High-yield algorithms, recognition patterns, and exam traps — built for rapid last-minute recall.
Come Let's Get SunBurned (Superficial → Deep) C – Stratum Corneum L – Stratum Lucidum G – Stratum Granulosum S – Stratum Spinosum B – Stratum Basale
| Layer | Key Features | Clinical Relevance |
|---|---|---|
| Stratum Corneum | Dead keratinocytes, main barrier | Psoriasis → hyperkeratosis |
| Stratum Lucidum | Only in thick skin (palms, soles) | Absent in thin skin |
| Stratum Granulosum | Keratohyalin granules | Lichen planus → hypergranulosis |
| Stratum Spinosum | "Prickle cell layer," desmosomes | Pemphigus vulgaris |
| Stratum Basale | Melanocytes, stem cells | Basal cell carcinoma arises here |
| Term | Definition | Size | Example |
|---|---|---|---|
| Macule | Flat, colour change | <1 cm | Freckle, vitiligo |
| Patch | Flat, colour change | >1 cm | Port-wine stain, café-au-lait |
| Papule | Raised, palpable | <1 cm | Mole, wart, acne |
| Plaque | Raised, plateau-like | >1 cm | Psoriasis |
| Nodule | Solid, deeper than papule | >1 cm | Lipoma, dermatofibroma |
| Vesicle | Fluid-filled blister | <0.5 cm | Chickenpox, herpes |
| Bulla | Large fluid-filled blister | >0.5 cm | Bullous pemphigoid |
| Pustule | Pus-filled | Any size | Acne, folliculitis |
| Wheal | Transient, oedematous | Variable | Urticaria (hives) |
| Term | Definition | Example |
|---|---|---|
| Scale | Flaking of stratum corneum | Psoriasis, ichthyosis |
| Crust | Dried serum, blood, or pus | Impetigo (honey-coloured) |
| Erosion | Loss of epidermis only | Pemphigus vulgaris |
| Ulcer | Loss of epidermis + dermis | Diabetic foot ulcer |
| Fissure | Linear crack | Chronic eczema on hands |
| Lichenification | Thick skin with exaggerated markings | Chronic atopic dermatitis |
| Atrophy | Thinning of skin | Steroid overuse, ageing |
| Scar | Fibrous tissue replacing normal skin | Post-injury, acne scars |
| Term | Definition | Disease Example |
|---|---|---|
| Hyperkeratosis | Thickened stratum corneum | Psoriasis, calluses |
| Parakeratosis | Retained nuclei in stratum corneum | Psoriasis |
| Acanthosis | Thickened stratum spinosum | Acanthosis nigricans |
| Acantholysis | Loss of cell-cell adhesion | Pemphigus vulgaris |
| Spongiosis | Intercellular oedema in epidermis | Eczema |
| Dyskeratosis | Abnormal keratinization | Squamous cell carcinoma |
Chronic relapsing inflammatory skin disease — epidermal barrier dysfunction + Type I hypersensitivity.
"Intensely pruritic flexural eczema with xerosis; all stages present simultaneously; ↑ IgE"
| Age | Distribution | Key Features |
|---|---|---|
| Infants <2 yrs | Face, scalp, extensor surfaces | Weeping crusted lesions; diaper area spared |
| Children 2-12 yrs | Flexural surfaces (antecubital, popliteal), neck | Dry, lichenified plaques |
| Adults | Hands, wrists, ankles, flexures | Lichenification, fissures |
Step 1: Avoid triggers — harsh soaps, hot water, allergens Step 2: Topical steroids: hydrocortisone 1% (face) · mometasone/betamethasone (body) · clobetasol short-term (severe) Step 3: Emollients: petroleum jelly, aqueous cream — most important for MAINTENANCE Step 4: Antihistamines: hydroxyzine at night for pruritus Step 5: Treat secondary infection: mupirocin topical / oral antibiotics Steroid-sparing: Topical calcineurin inhibitors (tacrolimus, pimecrolimus)
Eczema herpeticum — disseminated HSV superinfection on eczema = MEDICAL EMERGENCY → IV acyclovir Secondary bacterial infection (S. aureus) — impetiginized eczema
Mechanism: Type IV (delayed) hypersensitivity — develops 24–72 h AFTER exposure Types: Allergic (nickel, poison ivy, PPD/henna) vs Irritant (soaps, detergents, acids)
"Angular/linear distribution with sharp geometric borders exactly where allergen contacted skin"
Classic Pakistani triggers: Henna/PPD · Nickel jewellery · Rubber footwear · Kohl/fairness creams
Remove offending agent — most important step Topical steroids (moderate to potent) Systemic steroids if severe: prednisolone 0.5–1 mg/kg Antihistamines for pruritus
Contact dermatitis develops 24–72 hours AFTER exposure (delayed hypersensitivity) — NOT immediate
Chronic inflammatory dermatosis associated with Malassezia species. Key pattern: Greasy yellow scales on erythematous base — sebaceous areas only — minimal pruritus
| Age | Presentation | Management |
|---|---|---|
| Infants | Cradle cap: thick yellow scales on scalp, diaper rash | Emollients, gentle washing |
| Adults | Scalp dandruff, facial involvement | Antifungal shampoos |
| HIV/AIDS | Severe, widespread, refractory | Treat underlying immunodeficiency |
Scalp: ketoconazole 2% shampoo · selenium sulfide · zinc pyrithione Face/body: topical antifungals + mild topical steroids AVOID prolonged steroid on face → telangiectasias, atrophy
Chronic T-cell mediated inflammatory disease with epidermal hyperproliferation.
"Well-demarcated erythematous plaques with SILVERY SCALES on EXTENSOR surfaces"
Signs: Auspitz sign (pinpoint bleeding on scale removal) · Koebner phenomenon · Nail pitting/oil spots/onycholysis
| Type | Features | Age | Triggers |
|---|---|---|---|
| Plaque | Most common (90%), thick silvery scales | Adults | Stress, infections |
| Guttate | "Raindrop" papules on trunk | Children/Young adults | Strep throat |
| Pustular | Sterile pustules — von Zumbusch or localised | Adults | Steroid withdrawal |
| Erythrodermic | >90% BSA — MEDICAL EMERGENCY | Any age | Systemic illness |
| Inverse | Flexural, minimal scale | Adults | Obesity, friction |
Mild BSA <5%: Topical steroids (first-line) · Vitamin D analogs (calcipotriol) · Tar · Emollients Moderate BSA 5-10%: Phototherapy: PUVA or NB-UVB ± topical agents Severe BSA >10% / PsA: Methotrexate (most used in Pakistan) · Cyclosporine · Acitretin (pustular) Biologics: TNF-α inhibitors (etanercept, adalimumab) · IL-12/23 inhibitors (ustekinumab)
"Sausage digits" → Psoriatic arthritis (dactylitis) Sudden onset child + sore throat → Guttate psoriasis Drugs worsening psoriasis: β-blockers, lithium, antimalarials, NSAIDs, steroid withdrawal
The 6 P's of Lichen Planus Pruritic · Purple · Polygonal · Planar (flat-topped) · Papules · Plaques
"Purple flat-topped polygonal papules with Wickham striae on FLEXOR wrists"
Histology: "Sawtooth" rete ridges · Hypergranulosis · Band-like lymphocytic infiltrate at DEJ Association: Hepatitis C — check LFTs and serology
Potent topical steroids (first-line) Systemic steroids if severe Topical calcineurin inhibitors for oral lesions Self-limited — resolves in 1–2 years
"Herald patch → Christmas tree distribution along Langer lines 7–14 days later"
Herald patch: 2–10 cm, oval, salmon-coloured with collarette scale
Spares face, palms, soles (vs secondary syphilis which involves palms/soles)
Self-limited — 6–8 weeks spontaneous resolution
DIFFERENTIAL: Secondary syphilis involves palms & soles — check VDRL/RPR if sexually active
IMPETIGO — Most Common Skin Infection in Children
"Honey-coloured crusted lesions around mouth and nose in a child"
| Type | Organism | Features |
|---|---|---|
| Non-bullous | S. aureus, S. pyogenes | Honey-coloured crusts on erythematous base |
| Bullous | S. aureus (exotoxin) | Flaccid bullae that rupture easily — trunk, face |
Localised: Topical mupirocin 2% TID × 7–10 days Widespread/bullous: Oral flucloxacillin or cephalexin × 7 days MRSA suspected: Clindamycin or co-trimoxazole Complication: Post-streptococcal GN (PSGN) — check urine R/E. Rheumatic fever does NOT follow skin infections.
CELLULITIS — Classification by Depth
| Condition | Depth | Features | Organism |
|---|---|---|---|
| Erysipelas | Superficial dermis | Well-demarcated, raised, shiny red plaque; face common | GAS |
| Cellulitis | Deep dermis + subcut. | Ill-defined, warm, tender, red | S. aureus, GAS |
| Necrotizing Fasciitis | Fascia + muscle | Pain out of proportion, crepitus, dusky — SURGICAL EMERGENCY | Polymicrobial |
Mild outpatient: Oral flucloxacillin or cephalexin · elevate limb · treat tinea pedis Moderate-Severe: IV flucloxacillin or cefazolin · MRSA: add vancomycin or linezolid Necrotizing Fasciitis: SURGICAL EMERGENCY — immediate debridement + pip-tazo + vancomycin + ICU
Don't confuse cellulitis with DVT — both cause leg swelling, but DVT has NO erythema
HERPES SIMPLEX VIRUS (HSV)
| Type | Location | Transmission | Latency |
|---|---|---|---|
| HSV-1 | Orofacial (cold sores) | Oral secretions | Trigeminal ganglion |
| HSV-2 | Genital | Sexual contact | Sacral ganglion |
"Painful grouped vesicles on erythematous base — prodrome of tingling/burning precedes eruption"
Primary: Acyclovir 400 mg TID × 7–10 days OR valacyclovir 1 g BD × 7–10 days Recurrent: Start within 24 h of prodrome — acyclovir 400 mg TID × 5 days Suppressive: ≥6 recurrences/year → acyclovir 400 mg BD continuously Severe/immunocompromised: IV acyclovir
Eczema herpeticum — HSV on atopic eczema = MEDICAL EMERGENCY → IV acyclovir HSV-1 encephalitis → temporal lobe → IV acyclovir
VARICELLA-ZOSTER VIRUS (VZV)
| Disease | Type | Distribution | Contagious |
|---|---|---|---|
| Chickenpox | Primary infection | Generalised, centripetal | Highly — airborne + contact |
| Shingles (Herpes Zoster) | Reactivation | Unilateral dermatomal | Less — contact only |
"Chickenpox: crops at DIFFERENT stages simultaneously — dewdrop on rose petal appearance"
"Shingles: unilateral dermatomal vesicular rash — does NOT cross midline"
Hutchinson sign: vesicles on nasal tip → nasociliary involvement → risk of blindness (HZO)
Ramsay Hunt: ear vesicles + facial palsy + hearing loss
Chickenpox adults/immunocomp.: Acyclovir 800 mg 5× daily × 7 days Children: supportive Herpes Zoster — within 72 h: Acyclovir 800 mg 5× daily × 7 days OR valacyclovir 1 g TID × 7 days Postherpetic neuralgia: Gabapentin · Pregabalin · Amitriptyline
HPV — WARTS
| Type | HPV | Location | Features |
|---|---|---|---|
| Verruca vulgaris | 1,2,4 | Hands, fingers | Rough, hyperkeratotic — black dots = thrombosed capillaries |
| Plantar warts | 1,2 | Soles of feet | Painful, black dots |
| Flat warts | 3,10 | Face, hands | Smooth, flat-topped, multiple |
| Filiform warts | 1,2,4 | Face, neck | Thread-like projections |
| Condyloma acuminatum | 6,11 | Anogenital | Cauliflower-like — STI |
High-risk HPV 16, 18 → cervical cancer — NOT visible warts
First-line: Cryotherapy with liquid nitrogen — repeat every 2–3 weeks Alternatives: Topical salicylic acid 17–40% · Imiquimod (genital) · Podophyllin (genital — NOT in pregnancy)
MOLLUSCUM CONTAGIOSUM (Poxvirus)
"Flesh-coloured dome-shaped papules with central UMBILICATION — diagnostic sign"
Self-limited (6–12 months) · Children: trunk/extremities · Adults on genitals = STI
Giant molluscum in an adult → Think HIV / immunosuppression
DERMATOPHYTOSIS (TINEA)
Causative organisms: Trichophyton · Microsporum · Epidermophyton
| Type | Location | Features | Pakistan |
|---|---|---|---|
| Tinea capitis | Scalp | Scaly patches, alopecia, kerion (boggy mass) | Common (Children) |
| Tinea corporis | Body | Annular plaques with central clearing | Common |
| Tinea cruris | Groin | Pruritic — does NOT involve scrotum | Very common |
| Tinea pedis | Feet | Interdigital scaling, moccasin pattern | Common |
| Tinea unguium | Nails | Onychomycosis — thick, discoloured | Common |
| Tinea versicolor | Trunk/neck | Hypo/hyperpigmented macules | Very common |
Best initial test: KOH prep — septate hyphae (tinea) or spaghetti-and-meatballs (versicolor) Most accurate: Fungal culture — 2–4 weeks Wood's lamp: Only Microsporum fluoresces green — not routine
Topical (localised): Terbinafine cream BD × 2–4 weeks · Alt: clotrimazole, miconazole Oral ALWAYS for: Tinea capitis · Tinea unguium · Extensive/refractory disease Terbinafine 250 mg OD: Capitis: 4–6 wks · Unguium: 3 months Griseofulvin: Alternative for tinea capitis especially in children
Tinea incognito — tinea + topical steroids → atypical appearance, difficult to recognise Two feet one hand syndrome — tinea pedis + tinea manuum on dominant hand (scratching feet)
CANDIDIASIS
| Site | Features | Risk Factors |
|---|---|---|
| Oral thrush | White plaques — easily scraped off | Infants, antibiotics, steroids, HIV |
| Vulvovaginal | Thick white cottage cheese discharge, pruritus | Pregnancy, DM, antibiotics |
| Diaper dermatitis | Beefy red — inguinal folds + satellite lesions | Infants, wet diapers |
| Intertrigo | Red macerated rash in skinfolds | Obesity, DM, hot weather |
| Paronychia | Swollen nail fold, pus | Chronic water exposure |
Satellite lesions = DIAGNOSTIC of Candida · KOH: pseudohyphae + budding yeast
SCABIES
"Intense NOCTURNAL pruritus in MULTIPLE FAMILY MEMBERS — primary lesion is the BURROW"
Sites: Web spaces of fingers (MC) · Wrists · Axillary folds · Waistline · Genitals · Spares face in adults
First-line: Permethrin 5% cream — neck down, overnight 8–12 h, repeat after 1 week Alternative: Ivermectin 200 mcg/kg oral × 2 doses 1 week apart Pregnancy / infants <2 months: Sulfur 5–10% ointment CRITICAL: Treat ALL family members simultaneously · Wash all clothes/bedding in hot water Pruritus may persist 2–4 weeks post-treatment — hypersensitivity, NOT treatment failure
Crusted (Norwegian) Scabies — immunocompromised, thick crusts, HIGHLY contagious → ivermectin + permethrin combined
CUTANEOUS LEISHMANIASIS — endemic in Pakistan (KPK, Balochistan, Sindh)
"Painless chronic ulcer with raised VIOLACEOUS BORDER on exposed area — history of sandfly bite"
Cause: Leishmania tropica / L. major · Vector: Phlebotomus sandfly · Reservoir: dogs
| Type | Features | Pakistan |
|---|---|---|
| Localized CL | Single/few papules → nodules → painless ulcer with raised border | Very common |
| Lupoid leishmaniasis | Facial plaques, resembles lupus vulgaris (TB) | Common |
| Post-kala azar dermal | After visceral leishmaniasis treatment | Common (VL areas) |
| Diffuse CL | Multiple non-ulcerating nodules | Rare |
Slit skin smear: Amastigotes (Leishman-Donovan bodies) inside macrophages PCR: Most sensitive Culture: NNN medium
First-line Pakistan: Intralesional sodium stibogluconate (Pentostam) 0.5–2 mL — weekly × 4–6 weeks Systemic (multiple/facial): Sodium stibogluconate IM 20 mg/kg/day × 20 days OR Miltefosine 2.5 mg/kg/day × 28 days Prevention: Insect repellents · Bed nets · Treat dogs
CUTANEOUS LARVA MIGRANS
"Serpiginous snake-like track advancing mm/day after walking BAREFOOT on contaminated soil"
First-line: Ivermectin 200 mcg/kg single dose — repeat if needed Note: Self-limited weeks–months if untreated
Antibody target: IgG against DESMOGLEIN 3 (± desmoglein 1) Level: INTRAEPIDERMAL — acantholysis in stratum spinosum
"Flaccid blisters that rupture easily — oral erosions in 90% (often first sign) — Nikolsky POSITIVE"
Gold standard: Skin biopsy + Direct immunofluorescence (DIF) Histology: "Tombstone appearance" — basal cells remain attached; acantholysis above DIF: "Fishnet/net-like" pattern — IgG and C3 around keratinocytes Serology: Anti-desmoglein antibodies (ELISA)
Mainstay: High-dose prednisolone 1–2 mg/kg/day until no new blisters (4–6 weeks), then slow taper Steroid-sparing: Azathioprine · Mycophenolate mofetil · Rituximab (refractory)
High mortality if untreated — sepsis and fluid/electrolyte imbalance
Bullous Pemphigoid: IgG against hemidesmosomes (BP180, BP230) → SUBEPIDERMAL blistering
| Feature | Pemphigus Vulgaris | Bullous Pemphigoid |
|---|---|---|
| Blister type | Flaccid — rupture easily | Tense — intact |
| Mucosal involvement | Common (90%) | Rare |
| Nikolsky sign | Positive | NEGATIVE |
| Age | 40–60 years | >60 years (elderly) |
| Level | Intraepidermal | Subepidermal |
| DIF | Fishnet IgG around keratinocytes | Linear IgG at basement membrane |
| Prognosis | More severe | Better |
Strong association: Coeliac Disease (gluten sensitivity)
"Intensely pruritic grouped vesicles on EXTENSOR surfaces — patients scratch off blisters, see only excoriations"
DIF: Granular IgA deposits at dermal papillae tips — pathognomonic Check: Anti-tTG, anti-endomysial antibodies · Small bowel biopsy if indicated
Dapsone: Dramatic response within 48 hours — CHECK G6PD FIRST (risk of haemolysis) Long-term: Gluten-free diet
Autoimmune destruction of melanocytes → sharply demarcated DEPIGMENTED (white) macules and patches. Koebner positive: trauma → new lesions
Sites: Perioral · Periocular · Hands (dorsum) · Genitals · Extensor bony prominences
Associations: Thyroid disease (most common — Hashimoto's, Graves') · Type 1 DM · Pernicious anaemia · Addison's
Localised first-line: Potent topical steroids · Topical tacrolimus (face) Phototherapy: NB-UVB (preferred) · PUVA Rapidly progressive: Oral steroids pulse therapy Stable localised: Skin grafting · Melanocyte transplantation Always: Broad-spectrum sunscreen — prevent sunburn of depigmented areas
"Symmetric brown patches in mask-like distribution on face — women, darker skin Fitzpatrick IV–VI"
Triggers: Pregnancy · Oral contraceptives · Sun exposure · Cosmetics
Most important: Broad-spectrum sunscreen SPF 50+ and avoid triggers Triple combination cream: Hydroquinone 4% + Tretinoin 0.05% + Topical steroid Alternatives: Azelaic acid 20% · Kojic acid · Chemical peels · Laser
Recurrence very common despite treatment — sunscreen is maintenance, not optional
4 KEY PATHOGENIC FACTORS ↑ Sebum production (androgens) Follicular hyperkeratinization (plugging) Cutibacterium acnes colonisation Inflammation
| Grade | Lesions | Treatment |
|---|---|---|
| Mild — Comedonal | Blackheads, whiteheads, few papules | Topical retinoids (first-line) + benzoyl peroxide |
| Moderate — Papulopustular | Multiple papules, pustules | Above + oral doxycycline 100 mg BD × 3 months |
| Severe — Nodulocystic | Nodules, cysts, scarring | Oral isotretinoin 0.5–1 mg/kg/day × 4–6 months |
Isotretinoin cumulative dose target: 120–150 mg/kg | Monitor LFTs, lipids, pregnancy test MONTHLY
TERATOGENIC — two forms of contraception required in females on isotretinoin Acne fulminans: severe acne + fever + arthralgia → systemic steroids required Drug-induced acne (steroids, lithium, phenytoin) → monomorphic lesions — no comedones
"Adult acne" — but NOT acne. NO comedones. Central face. Triggers: sun, heat, alcohol, spicy food, stress.
"Central facial erythema + papules/pustules + NO comedones — fair-skinned adult 30–50 years"
| Subtype | Features |
|---|---|
| Erythematotelangiectatic | Persistent flushing, telangiectasias |
| Papulopustular | Papules, pustules — looks like acne |
| Phymatous | Thickened skin, rhinophyma (bulbous nose) |
| Ocular | Blepharitis, conjunctivitis |
Mild-Moderate: Topical metronidazole or azelaic acid · Topical ivermectin Moderate-Severe: Oral doxycycline 40 mg OD (anti-inflammatory dose) · Oral isotretinoin (refractory) Phymatous: Oral isotretinoin · Laser · Surgical debulking
Seborrhoeic Keratosis: "Stuck-on" waxy warty brown papules · >50 yrs · Benign — no malignant potential
Leser-Trélat sign: sudden appearance of MULTIPLE seborrhoeic keratoses → suspect GI adenocarcinoma
Dermatofibroma: Firm dome-shaped nodule · brown-pink · <1 cm · legs · "Dimple sign" when pinched
"Rough sandpaper-like patches on sun-exposed areas in elderly — 5–10% risk of SCC"
Field therapy: Topical 5-FU · Topical imiquimod 5% · Chemical peels Individual lesions: Cryotherapy (most common) · Curettage · Excision
BASAL CELL CARCINOMA (BCC) — Most Common Skin Cancer 70–80%
"Pearly translucent nodule with telangiectasias, rolled border, central ulceration (rodent ulcer)"
LOCALLY invasive — RARELY metastasises Sites: Face (nose, periorbital), scalp, ears
Surgical excision: With clear margins — cure rate >95% Mohs surgery: For cosmetically sensitive areas — face Alternatives: Cryotherapy, curettage, radiation for elderly/poor surgical candidates
SQUAMOUS CELL CARCINOMA (SCC) — Second Most Common
"Firm erythematous nodule/plaque with central ulceration and crust — keratin pearls on histology"
CAN METASTASISE — high-risk sites: lips, ears, genitals, chronic scars
Marjolin ulcer — SCC in chronic wound/burn scar — aggressive, high metastasis risk
MELANOMA — Most Dangerous Skin Cancer
ABCDE Rule — All suspicious pigmented lesions A — Asymmetry B — Border (irregular) C — Colour (variegated) D — Diameter (>6 mm) E — Evolving (changing)
| Type | Features | Site | Prognosis |
|---|---|---|---|
| Superficial spreading | Most common (70%), horizontal growth | Trunk/legs | Good if early |
| Nodular | Aggressive, vertical, dark nodule | Any | Poor |
| Lentigo maligna | Slow, elderly, sun-damaged | Face | Good |
| Acral lentiginous | Palms, soles, nails | Hands/feet | Common Asians/Blacks |
Breslow <1 mm → >95% 5-yr survival | Breslow 1–2 mm → 90% | 2–4 mm → 75% | >4 mm → ~50%
Localised: Wide local excision ± sentinel LN biopsy if >1 mm Metastatic: Immunotherapy (pembrolizumab, nivolumab) · BRAF inhibitors · Chemotherapy Follow-up: Lifelong surveillance — risk of second primary
"Symmetrical generalised maculopapular rash 7–14 days after starting drug — most common drug eruption"
Common drugs: penicillins, sulfonamides, anticonvulsants
Management: Stop drug · Antihistamines · Topical steroids
Life-threatening drug reaction — spectrum by body surface area (BSA) affected.
| Condition | BSA | Mortality |
|---|---|---|
| SJS | <10% | 5–10% |
| SJS-TEN overlap | 10–30% | 10–30% |
| TEN | >30% | 30–50% |
"Targetoid lesions + MUCOSAL involvement (oral/ocular/genital >90%) + positive Nikolsky sign"
High-risk drugs: Sulfonamides · Anticonvulsants (phenytoin, carbamazepine, lamotrigine) · Allopurinol · NSAIDs
MEDICAL EMERGENCY — ICU/Burn unit STOP offending drug immediately Supportive: fluid resuscitation, wound care, temperature regulation, nutrition Ophthalmology consult — prevent blindness Consider: IVIG, cyclosporine (both controversial) Prevent secondary infection
Sepsis = most common cause of death in SJS/TEN Long-term: blindness, oesophageal/urethral strictures
"Tender erythematous nodules on ANTERIOR SHINS — panniculitis (subcutaneous fat inflammation)"
NODOSUM — Causes N – No cause (idiopathic 50%) O – Oral contraceptives D – Drugs (sulfonamides) O – Osteomyelitis S – Sarcoidosis/Strep U – UC/Crohn's M – Microbiology (TB, leprosy)
Common in Pakistan: TB · Sarcoidosis · Strep infections
First-line: Treat underlying cause · NSAIDs · Rest and leg elevation Persistent: Potassium iodide
"Target lesions (3 concentric zones) on palms and soles — most commonly triggered by HSV"
Types: EM minor (skin only) · EM major (skin + mucosa) — Nikolsky NEGATIVE
Treat cause: Antivirals for HSV Recurrent HSV-associated EM: Suppressive acyclovir
"Transient pruritic oedematous wheals lasting <24 hours — Type I hypersensitivity"
Acute <6 weeks: identifiable trigger · Chronic >6 weeks: usually idiopathic
Non-sedating antihistamines: cetirizine, loratadine Sedating at night: hydroxyzine Systemic steroids if severe · Epinephrine if anaphylaxis Chronic urticaria: High-dose antihistamines or omalizumab
"Dark velvety patches in axillae, neck, groin — most commonly insulin resistance"
| Cause | Notes |
|---|---|
| Insulin resistance (DM, obesity, PCOS) | Most common |
| Malignancy (gastric adenocarcinoma) | If rapid onset — paraneoplastic |
| Drugs (niacin, corticosteroids) | Drug-induced |
| You see… | Think… |
|---|---|
| "Honey-coloured crust" | Impetigo |
| "Dewdrop on rose petal" | Chickenpox |
| "Herald patch" → Christmas tree | Pityriasis rosea |
| "Target lesions" (bulls eye) | Erythema multiforme |
| "Stuck-on appearance" | Seborrhoeic keratosis |
| "Pearly nodule with telangiectasias" | BCC |
| "Annular plaque with central clearing" | Tinea corporis |
| "Spaghetti and meatballs" on KOH | Tinea versicolor |
| "Satellite lesions" | Candidiasis |
| "Umbilicated papules" | Molluscum contagiosum |
| "Serpiginous track" | Cutaneous larva migrans |
| "Tombstone appearance" histology | Pemphigus vulgaris |
| "Silvery scales on extensor surfaces" | Psoriasis |
| "Wickham striae" | Lichen planus |
| "Oil drop sign" nails | Psoriatic nail disease |
| Nocturnal pruritus — multiple family members | Scabies |
| Positive Nikolsky sign | Pemphigus · TEN · SSSS |
| You see… | Think… |
|---|---|
| Auspitz sign | Psoriasis |
| Koebner phenomenon | Psoriasis · LP · Vitiligo |
| "Pain out of proportion" | Necrotizing fasciitis — EMERGENCY |
| Giant molluscum in adult | HIV/immunosuppression |
| Sausage digits + psoriasis | Psoriatic arthritis (dactylitis) |
| Sandfly bite + painless ulcer | Cutaneous leishmaniasis |
| "Butterfly rash" on face | SLE or Erysipelas |
| Condition / Drug | Key Number / Fact |
|---|---|
| SJS / TEN BSA thresholds | SJS <10% · Overlap 10–30% · TEN >30% |
| TEN mortality | 30–50% |
| Pemphigus — oral involvement | 90% — often first sign |
| Isotretinoin dose | 0.5–1 mg/kg/day · Cumulative 120–150 mg/kg |
| Scabies permethrin | Apply overnight 8–12 h — repeat after 1 week |
| Herpes zoster treatment window | Within 72 hours of rash onset |
| Postherpetic neuralgia definition | Pain >3 months after rash heals |
| BCC cure rate | ≥95% with excision |
| Melanoma Breslow <1 mm | ≥95% 5-year survival |
| Melanoma Breslow >4 mm | ~50% 5-year survival |
| Morbilliform eruption timing | 7–14 days after starting drug |
| Pityriasis rosea resolution | 6–8 weeks spontaneously |
| Dapsone response in DH | Dramatic within 48 hours |
| Tinea unguium terbinafine | 3 months oral |
| Leishmaniasis intralesional Rx | Weekly × 4–6 weeks |
| Q1 |
|---|
| A 25-year-old woman has intensely pruritic vesicles on elbows and knees. She has chronic diarrhoea. KOH prep negative. A) Atopic dermatitis B) Contact dermatitis C) Dermatitis herpetiformis D) Scabies |
| Answer |
|---|
| C) Dermatitis herpetiformis Associated with coeliac disease. Granular IgA at dermal papillae. Dapsone gives dramatic response in 48 h — check G6PD first. |
| Q2 |
|---|
| 60-year-old in rural KPK, diabetes. Painless shin ulcer with raised violaceous border for 6 months. A) Venous ulcer B) Arterial ulcer C) Cutaneous leishmaniasis D) Pyoderma gangrenosum |
| Answer |
|---|
| C) Cutaneous leishmaniasis Endemic in KPK. Painless ulcer with raised violaceous border on exposed areas. Diagnose with slit skin smear (amastigotes). |
| Q3 |
|---|
| 7-year-old child. Honey-coloured crusted lesions around nose and mouth. First-line for localised disease? A) Oral flucloxacillin B) IV vancomycin C) Topical mupirocin D) Oral azithromycin |
| Answer |
|---|
| C) Topical mupirocin Localised impetigo → topical mupirocin 2% TID × 7–10 days. Oral antibiotics are for widespread or bullous disease. |
| Q4 |
|---|
| 45-year-old woman. Tense blisters on trunk. Nikolsky negative. DIF shows linear IgG at basement membrane. A) Pemphigus vulgaris B) Bullous pemphigoid C) Dermatitis herpetiformis D) Epidermolysis bullosa |
| Answer |
|---|
| B) Bullous pemphigoid Tense blisters + negative Nikolsky + linear IgG at BMZ = bullous pemphigoid. Pemphigus has flaccid blisters, positive Nikolsky, fishnet DIF. |
| Q5 |
|---|
| Nocturnal pruritus in finger web spaces — multiple family members affected. A) Atopic dermatitis B) Scabies C) Dermatitis herpetiformis D) Contact dermatitis |
| Answer |
|---|
| B) Scabies Classic: nocturnal pruritus + web space burrows + multiple household members. First-line: permethrin 5% cream. |
| Q6 |
|---|
| 70-year-old man. Pearly nodule on nose with telangiectasias and central ulceration. Most likely behaviour? A) Metastasise to lymph nodes B) Metastasise to lungs C) Locally invasive, rarely metastasises D) Spontaneous regression |
| Answer |
|---|
| C) Locally invasive, rarely metastasises Basal cell carcinoma — most common skin cancer. Locally invasive but RARELY metastasises. Cure rate >95% with excision. |
| Q7 |
|---|
| Sharply demarcated depigmented patches on hands and periorbital area. Anti-thyroid antibodies positive. A) Tinea versicolor B) Pityriasis alba C) Vitiligo D) Post-inflammatory hypopigmentation |
| Answer |
|---|
| C) Vitiligo Autoimmune destruction of melanocytes. Most common autoimmune association = thyroid disease (Hashimoto's/Graves'). |
Correct: B) Parakeratosis
Concept: Histopathology terminology — parakeratosis Recall
Why B: Parakeratosis is retained nuclei in the stratum corneum, classically seen in psoriasis. Hyperkeratosis (thickened corneum) coexists in psoriasis but is not the retained-nuclei finding.
Discriminator: The stem asks specifically for the retained-nuclei feature, not the simple thickening.
| A) Hyperkeratosis | Hyperkeratosis is thickening of the stratum corneum — but no retained nuclei. |
| C) Acanthosis | Acanthosis is thickening of the stratum spinosum (e.g. acanthosis nigricans). |
| D) Spongiosis | Spongiosis is intercellular oedema of the epidermis — the hallmark of eczema. |
| E) Dyskeratosis | Dyskeratosis is abnormal premature keratinization, seen in squamous cell carcinoma. |
Trap: Term-swap — hyperkeratosis and parakeratosis coexist in psoriasis; the question targets the retained nuclei.
Future alert: Parakeratosis = retained nuclei in corneum → psoriasis; hyperkeratosis = thickened corneum without nuclei.
Correct: C) Acantholysis
Concept: Histopathology terminology — acantholysis Recall
Why C: Acantholysis is the loss of cell-cell adhesion (desmosome disruption), the defining lesion of pemphigus vulgaris.
Discriminator: "Loss of cell-cell adhesion" is the direct definition of acantholysis.
| A) Spongiosis | Spongiosis is intercellular oedema, typical of eczema — not loss of adhesion. |
| B) Parakeratosis | Parakeratosis is retained nuclei in the stratum corneum (psoriasis). |
| D) Hyperkeratosis | Hyperkeratosis is thickened stratum corneum, unrelated to adhesion loss. |
| E) Dyskeratosis | Dyskeratosis is abnormal premature keratinization, not loss of cohesion. |
Trap: Definition-flip — know acantholysis (adhesion loss) vs spongiosis (oedema); both involve the spinosum.
Future alert: Acantholysis → pemphigus group; spongiosis → eczema; memorise the pair.
Correct: D) Vesicle
Concept: Primary lesion classification — vesicle vs bulla Recall
Why D: A vesicle is a fluid-filled blister <0.5 cm; a bulla is >0.5 cm. Chickenpox vesicles fit the vesicle definition.
Discriminator: The size cut point (<0.5 cm) in the stem is the deliberate clue.
| A) Bulla | Bulla is a fluid-filled blister >0.5 cm — too large for these lesions. |
| B) Pustule | Pustule is pus-filled, not clear fluid. |
| C) Wheal | Wheal is a transient oedematous lesion (urticaria), not fluid-filled. |
| E) Nodule | Nodule is a solid lesion deeper than a papule (>1 cm). |
Trap: Size trap — the 0.5 cm cut-off separates vesicle from bulla; read the measurement.
Future alert: Vesicle <0.5 cm (chickenpox, herpes); bulla >0.5 cm (pemphigoid); pustule = pus.
Correct: E) Acanthosis
Concept: Histopathology terminology — acanthosis Recall
Why E: Acanthosis is thickening of the stratum spinosum — and it names the disease acanthosis nigricans.
Discriminator: "Thickened stratum spinosum" is the literal definition of acanthosis.
| A) Parakeratosis | Parakeratosis is retained nuclei in the stratum corneum (psoriasis). |
| B) Hyperkeratosis | Hyperkeratosis thickens the stratum corneum, not the spinosum. |
| C) Acantholysis | Acantholysis is loss of cell-cell adhesion (pemphigus). |
| D) Spongiosis | Spongiosis is intercellular oedema (eczema). |
Trap: Lookalike pair — acanthosis (thickening) vs acantholysis (breaking apart); one letter apart.
Future alert: Acanthosis = thickened spinosum; acantholysis = lost adhesion; do not swap.
Correct: A) Atopic dermatitis
Concept: Age-based distribution of atopic dermatitis Interpretation
Why A: Infantile atopic dermatitis classically affects face, scalp and extensor surfaces with sparing of the diaper area, with the atopic family history supporting it.
Discriminator: Infant age + extensor/face distribution + diaper-area sparing is the infantile atopic dermatitis pattern.
| B) Seborrheic dermatitis | Seborrheic dermatitis presents with greasy yellow scales on sebaceous areas (cradle cap), not weeping extensor lesions. |
| C) Contact dermatitis | Contact dermatitis follows a geometric allergen-contact distribution, not this age pattern. |
| D) Scabies | Scabies causes nocturnal pruritus with burrows in web spaces and affects family members. |
| E) Psoriasis | Psoriasis in infants is less typical and shows silvery scales, not weeping eczema. |
Trap: Age-distribution map — infants: face/extensors (diaper spared); children: flexures; adults: hands/wrists.
Future alert: Atopic dermatitis distribution flips extensor→flexural as the child grows.
Correct: B) Delayed Type IV hypersensitivity
Concept: Contact dermatitis mechanism — Type IV delayed hypersensitivity Interpretation
Why B: Allergic contact dermatitis is a Type IV delayed hypersensitivity developing 24-72 hours after allergen contact (here henna/PPD) — never immediate.
Discriminator: The 36-hour delay and the sharp geometric borders exactly matching the contact site are the decisive clues.
| A) Type I IgE-mediated immediate hypersensitivity | Type I IgE reactions are immediate (minutes), e.g. urticaria/anaphylaxis, not 36 hours later. |
| C) Type II antibody-mediated cytotoxicity | Type II reactions target cell-surface antigens with complement, not allergen contact sites. |
| D) Type III immune-complex deposition | Type III immune-complex disease (e.g. serum sickness) does not produce contact-bordered eruptions. |
| E) Direct irritant toxicity of the dye | Irritant dermatitis is dose-dependent chemical injury; allergic contact dermatitis is the delayed immune mechanism here. |
Trap: Timing trap — delayed (24-72 h) not immediate; classic MCQ discriminator for contact dermatitis.
Future alert: Contact dermatitis = 24-72 h delay; never answer "immediate hypersensitivity".
Correct: C) Emollients and gentle washing
Concept: Infantile seborrheic dermatitis (cradle cap) management Interpretation
Why C: In infants, cradle cap is managed with emollients and gentle washing; medicated ketoconazole shampoo is reserved for adult scalp involvement.
Discriminator: Age <2 years flips management from medicated shampoos to conservative emollients and washing.
| A) Ketoconazole 2% shampoo | Ketoconazole 2% shampoo is the adult scalp treatment, not first-line infant cradle cap care. |
| B) Potent topical corticosteroids | Prolonged steroids on the face are warned against (telangiectasias, atrophy); potent steroids are not first-line here. |
| D) Oral antifungal therapy | Oral antifungals are not used for uncomplicated infantile seborrheic dermatitis. |
| E) Topical tacrolimus | Topical calcineurin inhibitors are for steroid-sparing in eczema, not cradle cap. |
Trap: Age-shift — the same disease has different first-line management in infants vs adults.
Future alert: Cradle cap → emollients + gentle washing; adult scalp seborrheic dermatitis → ketoconazole shampoo.
Correct: D) IV acyclovir
Concept: Eczema herpeticum — disseminated HSV on eczema is an emergency Interpretation
Why D: Eczema herpeticum is disseminated HSV superinfection of eczematous skin and is a medical emergency requiring IV acyclovir.
Discriminator: "Punctuated vesicles + punched-out erosions + fever" in an atopic child is the eczema herpeticum pattern.
| A) Topical mupirocin to erosions | Mupirocin treats bacterial impetiginization, not disseminated HSV. |
| B) Oral antihistamines and observe | Observation with antihistamines would delay emergency antiviral therapy. |
| C) Increase topical steroid potency | More topical steroid is contraindicated — infection is the issue. |
| E) Oral flucloxacillin | Flucloxacillin covers bacteria, not HSV; this is a viral superinfection. |
Trap: Emergency override — eczema herpeticum outranks routine eczema care; answer IV acyclovir, not antibiotics.
Future alert: Eczema herpeticum = IV acyclovir; impetiginized eczema = mupirocin/oral antibiotics — know which is which.
Correct: E) Guttate psoriasis
Concept: Guttate psoriasis — strep-triggered raindrop papules Interpretation
Why E: Guttate psoriasis presents as raindrop-like papules on the trunk in children/young adults, typically 1-3 weeks after streptococcal pharyngitis.
Discriminator: Age + "raindrop" papules + recent sore throat are the guttate signature.
| A) Plaque psoriasis | Plaque psoriasis (90%) shows thick silvery scale on extensors, not acute raindrops. |
| B) Inverse psoriasis | Inverse psoriasis is flexural with minimal scale, driven by friction/obesity. |
| C) Pustular psoriasis | Pustular psoriasis shows sterile pustules (von Zumbusch or localised). |
| D) Erythrodermic psoriasis | Erythrodermic psoriasis covers >90% BSA and is a medical emergency. |
Trap: Subtype map — know which psoriasis fires after strep (guttate) vs on the extensors (plaque).
Future alert: Guttate psoriasis: child + strep → raindrop papules; plaque psoriasis: adult + extensor silvery scale.
Correct: A) Hepatitis C serology and LFTs
Concept: Lichen planus association with hepatitis C Interpretation
Why A: Lichen planus (pruritic, purple, polygonal, planar papules with Wickham striae) is associated with hepatitis C; LFTs and HCV serology are checked.
Discriminator: "Purple polygonal planar papules + Wickham striae on flexor wrists" is lichen planus, and the stem asks for its key association.
| B) Hepatitis B surface antigen | HBV is not the recognised lichen planus association — HCV is. |
| C) HIV antibody test | HIV does not drive lichen planus workup; molluscum/leishmaniasis vigilance does. |
| D) EBV serology | EBV is not linked with lichen planus. |
| E) CMV IgM | CMV is not part of lichen planus serology. |
Trap: Hepatitis letter swap — HCV (C) is the lichen planus association, not HBV.
Future alert: Lichen planus → check HCV serology + LFTs; remember the 6 Ps.
Correct: B) Palm and sole involvement
Concept: Pityriasis rosea vs secondary syphilis Interpretation
Why B: Pityriasis rosea spares the palms and soles; palm/sole involvement redirects to secondary syphilis (check VDRL/RPR), especially if sexually active.
Discriminator: Herald patch → Christmas tree is classic pityriasis rosea; palms/soles involvement is the syphilis red flag.
| A) Lesions distributed along Langer lines | Distribution along Langer lines is characteristic of pityriasis rosea, not a red flag. |
| C) Lesions with a fine collarette scale | Collarette scale is typical of the herald patch. |
| D) Spontaneous resolution expected by 6-8 weeks | Spontaneous resolution in 6-8 weeks is the expected pityriasis rosea course. |
| E) No lesion on the face | Facial sparing is expectable in pityriasis rosea. |
Trap: Cross-syndrome check — the source explicitly contrasts palms/soles (syphilis) with pityriasis rosea sparing them.
Future alert: Pityriasis rosea spares palms/soles; involvement there → VDRL/RPR for secondary syphilis.
Correct: C) Psoriatic arthritis with dactylitis
Concept: Psoriatic arthritis — dactylitis (sausage digit) Interpretation
Why C: Sausage digits are dactylitis — diffuse swelling of a whole digit from flexor tenosynovitis — a classic psoriatic arthritis manifestation; axial involvement is also seen.
Discriminator: "Sausage digit in a patient with psoriasis" maps straight to psoriatic arthritis with dactylitis.
| A) Osteoarthritis with Heberden nodes | Osteoarthritis targets DIP joints with Heberden nodes and sparing of the digit shaft-like swelling. |
| B) Rheumatoid arthritis pattern | Rheumatoid arthritis gives symmetric MCP/PIP synovitis, not whole-digit sausage swelling. |
| D) Gouty arthritis flare | Gout flares as acute podagra with exquisite metatarsophalangeal pain, not a whole swollen digit. |
| E) Septic arthritis | Septic arthritis is a single hot joint with fever — no psoriasis-linked digit pattern. |
Trap: Pattern match — "sausage digit + psoriasis" is dactylitis; do not reach for OA/RA.
Future alert: Dactylitis (sausage digit) → psoriatic arthritis; memorise the PsA patterns.
Correct: D) Staphylococcus aureus producing exfoliative toxin
Concept: Bullous impetigo — S. aureus exotoxin Interpretation
Why D: Bullous impetigo is caused by Staphylococcus aureus exotoxin producing flaccid bullae that rupture easily, typically on trunk and face.
Discriminator: "Flaccid bullae that rupture easily" is the bullous impetigo signature, contrasting with the honey-coloured crust of non-bullous impetigo.
| A) Streptococcus pyogenes | S. pyogenes (GAS) causes non-bullous impetigo with honey-coloured crusts, not flaccid bullae. |
| B) Streptococcus pneumoniae | S. pneumoniae is not an impetigo pathogen. |
| C) Pseudomonas aeruginosa | Pseudomonas is a hot-tub folliculitis/otitis pathogen, not bullous impetigo. |
| E) Candida albicans | Candida causes intertrigo and white plaques, not flaccid bullae. |
Trap: Bullous vs non-bullous — both are impetigo but the toxin-driven bullous form is staphylococcal.
Future alert: Bullous impetigo = S. aureus exotoxin; non-bullous = S. aureus + S. pyogenes.
Correct: E) Immediate surgical debridement with broad-spectrum IV antibiotics
Concept: Necrotizing fasciitis — surgical emergency Analysis
Why E: Pain out of proportion, crepitus and dusky skin over a swollen limb indicate necrotizing fasciitis — a surgical emergency needing immediate debridement plus broad-spectrum IV antibiotics.
Discriminator: The stem loads the red flags: diabetic host, pain out of proportion, crepitus, dusky colour.
| A) Oral flucloxacillin and limb elevation | Oral flucloxacillin treats mild cellulitis; it is dangerously inadequate for necrotizing fasciitis. |
| B) IV antibiotics with observation for 24 hours | Observation delays the only definitive therapy — surgery. |
| C) Warm compress and NSAIDs | Heat and NSAIDs mask a life-threatening emergency. |
| D) DVT ultrasound before any treatment | DVT gives unilateral swelling without crepitus or dusky skin; imaging first wastes time here. |
Trap: Emergency priority — crepitus + pain out of proportion override routine cellulitis care.
Future alert: Necrotizing fasciitis: pain out of proportion + crepitus + dusky skin → immediate surgery.
Correct: A) Trigeminal ganglion
Concept: HSV-1 latency — trigeminal ganglion Recall
Why A: HSV-1 remains latent in the trigeminal ganglion, reactivating as orofacial cold sores; HSV-2 instead enters the sacral ganglion for genital disease.
Discriminator: Orofacial HSV-1 selectively targets the trigeminal ganglion — the stem only mentions lip lesions.
| B) Sacral dorsal root ganglion | Sacral ganglion is the HSV-2 latency site for genital herpes. |
| C) Thoracic dorsal root ganglion | Thoracic dorsal root ganglia hold varicella-zoster, not HSV-1. |
| D) Trigeminal nucleus in the brainstem | Latency is in the peripheral sensory ganglion, not the brainstem nucleus. |
| E) Basal keratinocytes of the lip | Keratinocytes are the site of viral replication during reactivation, not latency. |
Trap: Ganglion map — HSV-1 trigeminal vs HSV-2 sacral vs VZV thoracic; do not swap.
Future alert: Latency map: HSV-1 → trigeminal ganglion; HSV-2 → sacral; VZV → dorsal root ganglia.
Correct: B) Herpes zoster ophthalmicus with risk of blindness
Concept: Hutchinson sign — nasociliary involvement, eye risk Interpretation
Why B: Vesicles on the nasal tip (Hutchinson sign) signal nasociliary nerve involvement and risk of herpes zoster ophthalmicus with corneal scarring and blindness — urgent ophthalmology.
Discriminator: Nasal tip + facial zoster is the Hutchinson sign; the stem asks for the complication it predicts.
| A) Postherpetic neuralgia | Postherpetic neuralgia is possible but not the specific nose-tip warning; the eye is the immediate concern. |
| C) Ramsay Hunt syndrome | Ramsay Hunt syndrome is zoster of the geniculate ganglion with facial palsy and ear pain. |
| D) Meningoencephalitis | Meningoencephalitis follows disseminated zoster, not a localised nasal tip lesion. |
| E) Secondary bacterial infection | Secondary infection is a general risk of any zoster, not the Hutchinson-specific one. |
Trap: Anatomy clue — "vesicles on the nasal tip" is the Hutchinson sign answer trigger.
Future alert: Hutchinson sign (nasal tip vesicles) → herpes zoster ophthalmicus → urgent ophthalmology.
Correct: C) Sulfur 5-10% ointment
Concept: Scabies in infants <2 months — sulfur ointment Recall
Why C: In pregnancy and infants under 2 months, permethrin and ivermectin are avoided; sulfur 5-10% ointment is the scabicide of choice.
Discriminator: The stem pins the age (<2 months), which flips the first-line choice to sulfur.
| A) Permethrin 5% cream | Permethrin 5% is the general first-line but is avoided in this age group (<2 months). |
| B) Oral ivermectin | Oral ivermectin is an alternative for older patients, not a 6-week-old infant. |
| D) Lindane lotion | Lindane is neurotoxic and should not be used in infants. |
| E) Benzyl benzoate | Benzyl benzoate is not the infant-first-line; sulfur is specified. |
Trap: Age-exception — the textbook first-line (permethrin) is wrong below 2 months; sulfur wins.
Future alert: Scabies: permethrin first-line; sulfur 5-10% in pregnancy/infants <2 months; treat all family members.
Correct: D) Pemphigus vulgaris
Concept: Pemphigus vulgaris — oral-first, acantholysis above basal layer Interpretation
Why D: Oral erosions as the first sign, flaccid blisters, positive Nikolsky, and suprabasal acantholysis with a tombstone row of basal cells are the pemphigus vulgaris signature.
Discriminator: Every clue sits in one camp: oral first + flaccid + Nikolsky positive + suprabasal acantholysis = PV.
| A) Bullous pemphigoid | Bullous pemphigoid gives tense blisters, negative Nikolsky, subepidermal split, elderly patients. |
| B) Dermatitis herpetiformis | Dermatitis herpetiformis is pruritic grouped vesicles on extensors with granular IgA. |
| C) Erythema multiforme | Erythema multiforme has target lesions, no acantholysis. |
| E) Epidermolysis bullosa | Epidermolysis bullosa is a genetic blistering disease of childhood, not this presentation. |
Trap: Clue pile-up — oral-first + tombstone basal row is PV, not the tense-blister mimics.
Future alert: PV: suprabasal acantholysis (tombstone row) + positive Nikolsky; BP: subepidermal + negative Nikolsky.
Correct: E) Hemidesmosomal proteins BP180/BP230
Concept: Bullous pemphigoid — anti-BP180/BP230 hemidesmosomal antibodies Recall
Why E: Bullous pemphigoid targets hemidesmosomal proteins BP180 (BPAG2) and BP230 (BPAG1) at the basement membrane zone, giving linear IgG on DIF.
Discriminator: The stem names the disease; the question is the molecular target — hemidesmosomes.
| A) Desmoglein 3 | Desmoglein 3 is the pemphigus vulgaris target, giving suprabasal acantholysis. |
| B) Desmoglein 1 | Desmoglein 1 is targeted in pemphigus foliaceus. |
| C) Type VII collagen | Type VII collagen is attacked in epidermolysis bullosa acquisita, not BP. |
| D) Tissue transglutaminase | Tissue transglutaminase relates to coeliac disease, a dermatitis herpetiformis association. |
Trap: Antibody-mapping — BP targets hemidesmosomes; the pemphigus group targets desmogleins.
Future alert: BP180/BP230 → hemidesmosomes; desmogleins → pemphigus; type VII collagen → EBA.
Correct: A) G6PD level
Concept: Dermatitis herpetiformis — dapsone and G6PD screening Interpretation
Why A: DH (pruritic grouped vesicles on extensors, granular IgA at dermal papillae, coeliac link) responds dramatically to dapsone, but dapsone causes haemolysis — check G6PD first.
Discriminator: The stem plants the DH diagnosis and the dapsone start; G6PD is the pre-dapsone safety check.
| B) Serum creatinine | Renal monitoring matters for other drugs; dapsone has haemolysis as its key risk in G6PD deficiency. |
| C) Thyroid function tests | Thyroid tests are not a dapsone prerequisite. |
| D) Chest X-ray | Chest X-ray screens sarcoidosis/TB, not dapsone toxicity. |
| E) Fasting plasma glucose | Glucose is unrelated to dapsone initiation. |
Trap: Drug-safety hook — every dapsone question in exams is about G6PD screening.
Future alert: Dapsone: dramatic 48-h response in DH, but check G6PD first (haemolysis risk).
Correct: B) Dapsone
Concept: Dermatitis herpetiformis — dapsone response within 48 h Recall
Why B: Dapsone produces a dramatic improvement in DH itching within 48 hours; long-term control relies on the gluten-free diet.
Discriminator: "Dramatic response within 48 hours" is the exam phrase attached to dapsone in DH.
| A) Cetirizine | Antihistamines blunt itch generally but do not give the dramatic 48-h DH response. |
| C) Oral prednisolone | Steroids are not first-line for DH; dapsone is. |
| D) Acyclovir | Acyclovir is an antiviral — irrelevant to DH. |
| E) Topical mometasone | Topical steroids help limited lesions but not the DH signature response. |
Trap: Phrase-lock — "dramatic within 48 hours" + DH = dapsone, every time.
Future alert: DH: itch responds to dapsone in 48 h; GFD is the long-term therapy.
Correct: C) Thyroid disease
Concept: Vitiligo — most common autoimmune association is thyroid disease Recall
Why C: Vitiligo is an autoimmune destruction of melanocytes; thyroid disease (hypo/hyperthyroidism) is the most commonly associated autoimmune condition, so screening is advised.
Discriminator: "Sharply demarcated depigmented macules + white forelock" is vitiligo; the question asks its classic association.
| A) Addison disease | Addison disease is associated but far less common than thyroid disease in vitiligo. |
| B) Pernicious anaemia | Pernicious anaemia is associated with vitiligo but is not the most frequent. |
| D) Type 1 diabetes mellitus | Type 1 diabetes co-occurs, but thyroid disease tops the list. |
| E) Coeliac disease | Coeliac disease links with dermatitis herpetiformis, not vitiligo. |
Trap: Most-common ladder — thyroid disease is the number one vitiligo association in exams.
Future alert: Vitiligo → screen thyroid; associations ladder: thyroid > others.
Correct: D) Topical tacrolimus
Concept: Vitiligo management — topical tacrolimus for facial lesions Interpretation
Why D: Localised vitiligo is treated with potent topical steroids or topical tacrolimus on the face (steroid-sparing, avoids steroid atrophy); phototherapy (NB-UVB preferred) is the mainstay for more extensive disease.
Discriminator: The stem pins two facts: localised + facial — which selects topical tacrolimus.
| A) Oral PUVA as first line | Oral PUVA is not first-line; NB-UVB phototherapy is preferred and reserved for extensive disease. |
| B) Systemic corticosteroid pulses | Rapidly progressive disease uses oral steroid pulses, not stable localised lesions. |
| C) Skin grafting | Skin grafting is for stable, small lesions, not the immediate first-line choice. |
| E) Hydroquinone | Hydroquinone lightens hyperpigmentation — it would worsen depigmented vitiligo. |
Trap: Location and stability drive vitiligo management — face shifts to tacrolimus.
Future alert: Vitiligo: localised → potent steroids/tacrolimus (face); extensive → NB-UVB; grafting for stable small areas.
Correct: E) Strict broad-spectrum SPF 50+ sunscreen and trigger avoidance
Concept: Melasma — sunscreen and trigger avoidance are the foundation Interpretation
Why E: Melasma is driven by UV and hormones; strict SPF 50+ broad-spectrum sunscreen and avoiding triggers (sun, OCPs, cosmetics) form the cornerstone, with depigmenting agents added for active lesions.
Discriminator: Pregnancy + symmetric cheek hyperpigmentation = melasma; every guideline leads with protection, not creams.
| A) Triple combination cream alone | Triple combination cream works for active lesions but is never the sole first step and is avoided in pregnancy. |
| B) Chemical peeling as first-line | Chemical peels are adjuncts, not first-line. |
| C) Monotherapy with azelaic acid | Azelaic acid is an option for those avoiding hydroquinone, not the cornerstone. |
| D) Kojic acid serum only | Kojic acid is a mild adjunct, not the primary management. |
Trap: Foundation-first — melasma management always starts with sunscreen, not the cosmetic cream.
Future alert: Melasma: SPF 50+ and trigger avoidance first; topical depigmenting agents second.
Correct: A) Oral contraceptives
Concept: Melasma triggers — OCPs, pregnancy, sun, cosmetics Recall
Why A: Melasma is triggered by sun exposure, pregnancy, oral contraceptives and cosmetics; stopping the OCP may improve it.
Discriminator: The stem describes melasma on OCPs; the pill is itself the classic trigger in this list.
| B) Streptococcal pharyngitis | Streptococcal pharyngitis triggers guttate psoriasis, not melasma. |
| C) Lithium therapy | Lithium worsens psoriasis and can cause drug-induced acne, not melasma. |
| D) Dairy intake | Dietary history is irrelevant to melasma; drugs and UV are the triggers. |
| E) Cold exposure | Cold exposure is not a melasma trigger; sun is. |
Trap: Trigger list recall — sun, pregnancy, OCPs, cosmetics are the melasma quartet.
Future alert: Melasma triggers: sun, pregnancy, OCPs, cosmetics — remove/modify them.
Correct: B) Doxycycline 100 mg BD for 3 months
Concept: Moderate papulopustular acne — oral doxycycline Interpretation
Why B: Moderate inflammatory acne (papules and pustules, no nodules) is treated with a tetracycline — doxycycline 100 mg BD for about 3 months — added to topical therapy.
Discriminator: Nodule-free inflammatory acne defines moderate severity; that is the doxycycline tier, not isotretinoin.
| A) Isotretinoin as first-line | Isotretinoin is reserved for severe nodulocystic acne or treatment failure — not first-line here. |
| C) Minocycline 1 g once daily | Minocycline dose is 50-100 mg BD (not 1 g daily) and is a second-line tetracycline option. |
| D) Co-trimoxazole | Co-trimoxazole is not standard first-line acne therapy. |
| E) Topical erythromycin alone | Topical erythromycin alone is inadequate for widespread inflammatory lesions. |
Trap: Severity ladder — nodules/scars push to isotretinoin; papulopustular-only stays on doxycycline.
Future alert: Moderate acne → doxycycline 100 mg BD × 3 months; nodulocystic → isotretinoin.
Correct: C) Two forms of contraception and monthly pregnancy testing
Concept: Isotretinoin — teratogenicity requires dual contraception plus pregnancy tests Recall
Why C: Isotretinoin is profoundly teratogenic; females need two forms of contraception plus monthly pregnancy tests, along with monthly LFTs and lipid monitoring.
Discriminator: Isotretinoin + woman of reproductive age — the exam answer is always dual contraception.
| A) Monthly eye examination | Ophthalmology review is not the mandatory monthly monitor; teratogenicity is the core concern. |
| B) Weekly full blood count | LFTs and lipids are the blood monitors — monitored monthly, not weekly FBC. |
| D) Annual electrocardiogram | ECG is not part of isotretinoin monitoring. |
| E) Renal ultrasound | Renal imaging has no role in isotretinoin care. |
Trap: Drug-safety priority — teratogenicity beats every other monitoring detail for isotretinoin.
Future alert: Isotretinoin: dual contraception + monthly pregnancy test, LFTs, lipids; cumulative 120-150 mg/kg.
Correct: D) Systemic corticosteroids
Concept: Acne fulminans — systemic corticosteroids required Analysis
Why D: Acne fulminans (ulcerating acne with fever and arthralgia) is a systemic inflammatory eruption that requires systemic corticosteroids, typically with cautious isotretinoin later.
Discriminator: Sudden ulcerating acne + fever + arthralgia is the acne fulminans triad — corticosteroids, not routine acne drugs.
| A) Begin isotretinoin at full dose | Full-dose isotretinoin can flare acne fulminans further; it is introduced cautiously after steroids. |
| B) Oral doxycycline alone | Doxycycline treats ordinary inflammatory acne but not the systemic flares of fulminans. |
| C) Topical retinoids only | Topical therapy is far too weak for a febrile illness. |
| E) Reassurance with 6-week review | Reassurance is wrong — fever and ulceration need treatment. |
Trap: Distinct entity — fever + arthralgia moves the answer from acne routine to systemic steroids.
Future alert: Acne fulminans: ulcerating acne + fever + arthralgia → systemic corticosteroids.
Correct: E) Rosacea
Concept: Rosacea — central-face erythema/papules, flushing, no comedones Interpretation
Why E: Rosacea presents with central facial flushing, erythema and papules in middle-aged fair-skinned patients; the absence of comedones is the key discriminator from acne vulgaris.
Discriminator: "Central face + flushing + never had comedones" is the rosacea template.
| A) Acne vulgaris | Acne vulgaris requires comedones — explicitly absent here. |
| B) Perioral dermatitis | Perioral dermatitis clusters small papules around the mouth and often spares the nasal-forehead axis. |
| C) Atopic dermatitis | Atopic dermatitis is eczematous with pruritus, distributed flexurally, not central-face flushing. |
| D) Allergic contact dermatitis | Contact dermatitis is a geometric, contact-site eruption, not a fixed central-face pattern. |
Trap: Comedone gate — no comedones separates rosacea from acne vulgaris.
Future alert: Rosacea: central-face flushing/papules, no comedones; rhinophyma is the phymatous end.
Correct: A) Face
Concept: Mohs surgery — cosmetically sensitive facial locations Recall
Why A: Mohs micrographic surgery is preferred for BCC in cosmetically sensitive areas such as the face, where tissue-sparing margin control matters; excisional surgery elsewhere cures >95%.
Discriminator: The stem asks where Mohs is added — the face is the specified cosmetically sensitive zone.
| B) Back | Back lesions are low-risk sites where simple excision with clear margins suffices. |
| C) Lower legs | Lower legs are non-cosmetic sites; simple excision is standard. |
| D) Abdomen | Abdomen is not a Mohs-priority site. |
| E) Forearms | Forearms do not carry the facial cosmetic-tissue concern. |
Trap: Site-specific surgery — Mohs = face/cosmetically sensitive; trunk/extremities = simple excision.
Future alert: BCC: surgical excision with clear margins (cure >95%); Mohs for face; cryotherapy/radiation for poor candidates.
Correct: B) Squamous cell carcinoma arising in a chronic scar
Concept: Marjolin ulcer — SCC in a chronic wound or burn scar Interpretation
Why B: A Marjolin ulcer is a squamous cell carcinoma arising in a chronic wound or burn scar — it is aggressive with high metastatic potential.
Discriminator: "Ulcer inside a chronic burn scar + invasive keratinocytes" defines Marjolin ulcer.
| A) Viral-induced benign ulcer | The biopsy proof of invasion excludes any benign process. |
| C) Basal cell carcinoma variant with pearly borders | BCC shows basaloid islands and pearly borders, not keratinocyte invasion in a scar. |
| D) Stage IV pressure ulcer | Pressure ulcer is a non-neoplastic wound due to immobility, not scar-site carcinoma. |
| E) Pyoderma gangrenosum | Pyoderma gangrenosum is an inflammatory ulcer with undermined violaceous borders, not malignant cells. |
Trap: Name lock — chronic scar + SCC = Marjolin ulcer; expect the "aggressive, metastatic" follow-up.
Future alert: Marjolin ulcer = SCC in chronic scar/burn wound — aggressive, high metastasis risk.
Correct: C) Acral lentiginous melanoma
Concept: Acral lentiginous melanoma — palms, soles, nail beds; common in dark skin Interpretation
Why C: Acral lentiginous melanoma arises on palms, soles and subungual sites and is the most common melanoma subtype in Asian and Black populations.
Discriminator: "Sole of the foot in a dark-skinned patient" is the acral lentiginous location clue.
| A) Superficial spreading melanoma | Superficial spreading melanoma is the commonest subtype in fair-skinned populations on intermittently sun-exposed skin. |
| B) Nodular melanoma | Nodular melanoma is a rapidly growing nodule but is not site-selective for the sole. |
| D) Lentigo maligna melanoma | Lentigo maligna melanoma occurs on chronically sun-damaged facial skin of the elderly. |
| E) Desmoplastic melanoma | Desmoplastic melanoma is an uncommon sclerosing variant, not the sole-predominant type. |
Trap: Population-site map — acral lentiginous owns palms/soles/nail beds, especially in darker skin.
Future alert: Acral lentiginous melanoma: palms, soles, subungual — commonest subtype in Asian/Black patients.
Correct: D) About 90%
Concept: Melanoma prognosis — Breslow thickness strata Recall
Why D: Breslow thickness drives melanoma survival: <1 mm has >95%, 1-2 mm about 90%, 2-4 mm about 75% and >4 mm about 50% 5-year survival.
Discriminator: The stem fixes Breslow at 1.5 mm — squarely in the 1-2 mm band (about 90%).
| A) About 50% | About 50% corresponds to >4 mm Breslow thickness. |
| B) Greater than 95% | Greater than 95% applies to lesions thinner than 1 mm. |
| C) About 75% | About 75% belongs to the 2-4 mm group. |
| E) About 60% | About 60% is not one of the strata given for the classic bands. |
Trap: Number-band mapping — 1-2 mm is the 90% tier; memorise the four survival bands.
Future alert: Breslow survival: <1 mm >95%; 1-2 mm 90%; 2-4 mm 75%; >4 mm ~50%.
Correct: E) Wide local excision and sentinel lymph node biopsy
Concept: Sentinel lymph node biopsy for melanoma >1 mm Interpretation
Why E: Melanomas thicker than 1 mm undergo wide local excision plus sentinel lymph node biopsy for staging and prognosis.
Discriminator: The 1.8 mm thickness crosses the >1 mm threshold — that is the sentinel node indication.
| A) No further intervention | Lesions >1 mm need nodal staging — doing nothing is incomplete management. |
| B) Wide local excision alone is always sufficient | Wide excision alone is acceptable only for thinner (in situ/<1 mm) tumours. |
| C) Radiotherapy as primary treatment | Radiotherapy is not primary treatment for melanoma. |
| D) Systemic chemotherapy first | Chemotherapy is not a first-line staging step; surgery and nodal assessment come first. |
Trap: Threshold recall — the >1 mm Breslow cut-off triggers sentinel lymph node biopsy.
Future alert: Melanoma >1 mm → wide excision + sentinel lymph node biopsy; <1 mm → wide excision alone.
Correct: A) Morbilliform drug eruption
Concept: Morbilliform eruption — the commonest drug reaction pattern Interpretation
Why A: A symmetrical maculopapular rash beginning 7-14 days after a culprit drug (amoxicillin) is the classic morbilliform drug eruption — the most common pattern of drug eruption.
Discriminator: Timing (10 days), symmetry, and the absence of fever and mucosal lesions favour morbilliform over its mimics.
| B) Stevens-Johnson syndrome | SJS requires blistering and mucosal involvement with a rapidly progressive necrolysis. |
| C) Scabies | Scabies gives nocturnal pruritus with burrows in web spaces. |
| D) Measles | Measles presents with fever, cough, coryza and conjunctivitis before the rash. |
| E) Erythema multiforme | Erythema multiforme shows target lesions, predominantly on palms and soles. |
Trap: Prototype pattern — symmetrical maculopapular + new drug = morbilliform until proven otherwise.
Future alert: Morbilliform = most common drug eruption, 7-14 days after drug, symmetric maculopapular.
Correct: B) Toxic epidermal necrolysis with 30-50% mortality
Concept: TEN — >30% BSA detachment, 30-50% mortality Interpretation
Why B: Epidermal detachment over 40% BSA in a drug reaction is toxic epidermal necrolysis (>30% BSA), carrying a 30-50% mortality; SJS is <10% BSA and overlap 10-30%.
Discriminator: The 40% BSA figure places the case beyond SJS and overlap into TEN territory.
| A) Stevens-Johnson syndrome with about 10% mortality | SJS is <10% BSA detachment; 40% is far beyond it. |
| C) SJS-TEN overlap with near-universal survival | Overlap is 10-30% BSA — not 40%, and survival is far from universal. |
| D) Erythema multiforme major with <5% mortality | Erythema multiforme has target lesions and no widespread necrolysis. |
| E) Staphylococcal scalded skin syndrome with low mortality | SSSS is staphylococcal, affects young children, and spares mucosal surfaces. |
Trap: BSA ladder — SJS <10%, overlap 10-30%, TEN >30% with 30-50% mortality.
Future alert: TEN >30% BSA, mortality 30-50%; SJS <10%; overlap in between.
Correct: C) Sepsis
Concept: SJS/TEN — sepsis is the leading cause of death Recall
Why C: Skin barrier loss in SJS/TEN leads to infection; sepsis and multiorgan failure are the most common causes of death.
Discriminator: "Most common cause of death" in SJS/TEN is a fixed exam fact — sepsis.
| A) Hypovolaemia | Fluid loss matters but infection dominates mortality. |
| B) Renal failure | Renal failure usually follows sepsis rather than being the primary killer. |
| D) Cardiac arrhythmia | Arrhythmias are not the leading terminal event in SJS/TEN. |
| E) Pulmonary embolism | Pulmonary embolism is not a characteristic SJS/TEN mortality cause. |
Trap: Fixed fact — barrier loss → sepsis → death; the burn-unit analogy predicts the answer.
Future alert: SJS/TEN: sepsis is the most common cause of death — surveillance for infection is key.
Correct: D) Allopurinol
Concept: High-risk SJS/TEN drugs — sulfonamides, anticonvulsants, allopurinol, NSAIDs Recall
Why D: Allopurinol is one of the classic high-risk drugs for SJS/TEN, along with sulfonamides, anticonvulsants (phenytoin, carbamazepine, lamotrigine) and NSAIDs.
Discriminator: The stem asks for the recognised high-risk trigger; only allopurinol is on that list.
| A) Oral contraceptives | OCPs are not an SJS/TEN trigger list drug. |
| B) Paracetamol | Paracetamol is a common drug but not a high-risk SJS/TEN name. |
| C) Metformin | Metformin is not among the classic high-risk drugs. |
| E) Domperidone | Domperidone is a prokinetic, not a recognised SJS/TEN trigger. |
Trap: Trigger list recall — sulfonamides, anticonvulsants, allopurinol, NSAIDs are the big four.
Future alert: SJS/TEN high-risk drugs: sulfonamides, anticonvulsants (phenytoin, carbamazepine, lamotrigine), allopurinol, NSAIDs.
Correct: E) Tuberculosis, sarcoidosis and streptococcal infection
Concept: Erythema nodosum — TB, sarcoidosis, streptococcal causes Interpretation
Why E: Erythema nodosum (tender anterior shin nodules = septal panniculitis) is a reactive pattern; in our setting TB, sarcoidosis and streptococcal infection head the workup list.
Discriminator: Tender shin nodules = erythema nodosum; the question localises the cause list to Pakistan, where TB leads.
| A) Systemic lupus erythematosus | SLE is not a primary cause of erythema nodosum. |
| B) Candidiasis | Candidiasis does not produce shin nodules. |
| C) Rheumatoid arthritis | Rheumatoid arthritis is not an erythema nodosum cause. |
| D) Drug allergy | Drugs are a recognised cause but fungal "drug allergy" is not the lead answer in this setting. |
Trap: Setting-shifted workup — the geographically relevant list (TB/sarcoid/strep) beats generic causes.
Future alert: Erythema nodosum: tender anterior shin nodules; Pakistan workup → TB, sarcoidosis, strep.
Correct: A) Early or suppressive antiviral therapy with acyclovir
Concept: Erythema multiforme — HSV-triggered, treat the trigger with antivirals Interpretation
Why A: Recurrent erythema multiforme is most often triggered by herpes simplex; early (or suppressive) acyclovir reduces recurrences, whereas steroids are not first-line.
Discriminator: "Target lesions + cold sore trigger" is the HSV-driven recurrent EM pattern — treat HSV.
| B) Systemic corticosteroids as first-line | Systemic steroids are not first-line for HSV-triggered EM and may worsen the viral trigger. |
| C) Dapsone | Dapsone is for dermatititis herpetiformis, not EM. |
| D) Topical antifungal therapy | Antifungals target tinea, not EM. |
| E) Surgical debridement | Debridement belongs to necrotizing infections, not EM. |
Trap: Trigger therapy — recurrent EM answers with antivirals against the HSV driver.
Future alert: Erythema multiforme: target lesions, palms/soles, HSV-triggered → early/suppressive acyclovir.
Correct: B) High-dose nonsedating antihistamines, with omalizumab if refractory
Concept: Chronic urticaria — high-dose nonsedating antihistamines, escalation to omalizumab Interpretation
Why B: Chronic urticaria (>6 weeks) is managed with step-up high-dose nonsedating antihistamines; refractory cases escalate to omalizumab.
Discriminator: Wheals <24 h for >6 weeks defines chronic urticaria — antihistamine step-up is the pathway.
| A) Stop all suspect foods and recheck alone | Diet elimination alone is not the management; chronic urticaria is mostly idiopathic. |
| C) Long-term systemic corticosteroids | Long-term systemic steroids are avoided due to adverse effects. |
| D) Oral doxycycline | Doxycycline treats acne, not urticaria. |
| E) Topical corticosteroids alone | Topical steroids do not control generalised wheals. |
Trap: Duration threshold — >6 weeks flips acute management into the chronic urticaria path.
Future alert: Chronic urticaria (>6 weeks): step-up nonsedating antihistamines; omalizumab for refractory cases.
Correct: C) Insulin resistance
Concept: Acanthosis nigricans — insulin resistance is the commonest association Interpretation
Why C: Acanthosis nigricans (velvety hyperpigmentation of flexures) is most commonly a marker of insulin resistance; sudden rapid onset should raise suspicion for a paraneoplastic cause.
Discriminator: Axillary/neck velvety darkening in an obese adult points to insulin resistance, not an endocrine tumour.
| A) Adrenal insufficiency | Adrenal insufficiency gives diffuse hyperpigmentation (mucous membranes, palmar creases), not velvety flexural patches. |
| B) Thyroid carcinoma | Thyroid carcinoma is not a recognised acanthosis nigricans association. |
| D) Coeliac disease | Coeliac disease associates with dermatitis herpetiformis, not this finding. |
| E) Cushing syndrome | Cushing syndrome has striae, moon face and central obesity — not velvety flexural darkening. |
Trap: Marker logic — flexural velvety darkening = insulin resistance; rapid onset flips the thinking to malignancy.
Future alert: Acanthosis nigricans = insulin resistance (common); rapid onset → paraneoplastic (gastric adenocarcinoma).
Correct: D) Dewdrop on a rose petal
Concept: Buzzword — dewdrop on a rose petal = chickenpox Recall
Why D: "Dewdrop on a rose petal" describes chickenpox: clear vesicles (dewdrop) on an erythematous base (rose petal), present at different stages simultaneously.
Discriminator: Crops of vesicles at differing stages in a child is the classic chickenpox description.
| A) Honey-coloured crusted lesions | Honey-coloured crusts are the impetigo signature. |
| B) Herald patch | A herald patch precedes the Christmas-tree rash of pityriasis rosea. |
| C) Spaghetti-and-meatballs on KOH | Spaghetti-and-meatballs refers to tinea versicolor on KOH. |
| E) Target lesions | Target lesions belong to erythema multiforme. |
Trap: Phrase match — the stem itself mirrors the definition; "dewdrop + rose petal" = chickenpox.
Future alert: Buzzwords: dewdrop on rose petal = chickenpox; honey-coloured crust = impetigo; herald patch = PR.
Correct: E) Necrotizing fasciitis — surgical emergency
Concept: Buzzword — pain out of proportion = necrotizing fasciitis Recall
Why E: "Pain out of proportion" over a swollen limb is the buzzword for necrotizing fasciitis, a surgical emergency, until proven otherwise.
Discriminator: The phrase is the exam trigger; the answer must name the emergency.
| A) Cellulitis | Cellulitis is tender but the pain is proportionate to the erythema. |
| B) Deep vein thrombosis | DVT presents with swelling, not pain out of proportion or systemic toxicity. |
| C) Erysipelas | Erysipelas is a well-demarcated superficial infection with proportionate pain. |
| D) Simple abscess | An abscess is localised and fluctuant, not diffusely overwhelming pain. |
Trap: Buzzword reflex — the phrase maps to necrotizing fasciitis; mention surgery in the answer.
Future alert: "Pain out of proportion" → necrotizing fasciitis → immediate surgical debridement.
Correct: A) Tinea versicolor
Concept: Buzzword — spaghetti-and-meatballs on KOH = tinea versicolor Recall
Why A: The "spaghetti and meatballs" appearance (short hyphae + spores) on KOH is diagnostic of tinea versicolor (Malassezia).
Discriminator: The phrase is the answer key; hypopigmented chest patches reinforce tinea versicolor.
| B) Tinea corporis | Tinea corporis shows long septate hyphae, not the mixed hyphae-spore pattern. |
| C) Candidiasis | Candidiasis shows budding yeast and pseudohyphae, not this pattern. |
| D) Onychomycosis | Onychomycosis affects nails and shows hyphae on nail clippings. |
| E) Erythrasma | Erythrasma is bacterial (Corynebacterium) with coral-red fluorescence under Wood lamp. |
Trap: Phrase-grounded — spaghetti-and-meatballs is fixed to tinea versicolor, not other tinea.
Future alert: Spaghetti-and-meatballs on KOH → tinea versicolor; confirm with the phrase in stems.
Correct: B) Within 72 hours of rash onset
Concept: Power number — zoster antivirals within 72 hours Recall
Why B: Antivirals (acyclovir/valacyclovir) for herpes zoster must be started within 72 hours of rash onset to reduce acute pain and the risk of postherpetic neuralgia.
Discriminator: The stem asks the therapy window — 72 hours from rash onset is the fixed number.
| A) Within 1 week of crusting | Crusting means the replicative phase has passed; starting then is too late for maximal benefit. |
| C) Only after postherpetic neuralgia develops | Waiting for PHN is wrong — antivirals are preventive, given early. |
| D) Only in immunocompromised patients | Antivirals benefit immunocompetent patients within the window as well. |
| E) At any time up to 2 weeks | The benefit falls off sharply after 72 hours, not 2 weeks. |
Trap: Number lock — 72 hours is the zoster antiviral window; do not stretch it.
Future alert: Zoster antivirals within 72 hours of rash onset; PHN = pain >3 months after healing.
Correct: C) Postherpetic neuralgia
Concept: Power number — PHN is pain persisting beyond 3 months Recall
Why C: Postherpetic neuralgia is defined as pain persisting more than 3 months after the zoster rash has healed.
Discriminator: Persistent pain at 4 months crosses the 3-month post-healing threshold — PHN.
| A) Acute zoster pain | Acute zoster pain accompanies the active rash phase, not months after healing. |
| B) Recurrent herpes zoster | Recurrent zoster would show a new rash, not pain alone. |
| D) Chronic pruritus syndrome | Pruritus is itch, not pain. |
| E) HSV reactivation | HSV reactivation produces vesicles, not isolated persistent pain. |
Trap: Threshold number — >3 months of pain after healing is the PHN definition.
Future alert: PHN = pain >3 months after zoster healing; risk factors: age, severe acute pain.
Correct: D) 120-150 mg/kg
Concept: Power number — isotretinoin cumulative dose 120-150 mg/kg Recall
Why D: The standard cumulative isotretinoin target is 120-150 mg/kg (at 0.5-1 mg/kg/day), which lowers relapse rates in severe acne.
Discriminator: The stem asks the cumulative target — 120-150 mg/kg is the fixed power number.
| A) 50-75 mg/kg | 50-75 mg/kg is far below the relapse-reducing cumulative target. |
| B) 80-100 mg/kg | 80-100 mg/kg is insufficient as a course target. |
| C) 200-250 mg/kg | 200-250 mg/kg exceeds the standard course and adds toxicity without benefit. |
| E) 300 mg/kg | 300 mg/kg is above the accepted cumulative range. |
Trap: Number lock — cumulative 120-150 mg/kg; daily dose is 0.5-1 mg/kg/day — do not mix.
Future alert: Isotretinoin: 0.5-1 mg/kg/day, cumulative 120-150 mg/kg; monitor LFTs, lipids, pregnancy.
Correct: E) Phlebotomus sandfly
Concept: Cutaneous leishmaniasis — Phlebotomus sandfly vector Interpretation
Why E: A painless chronic ulcer with a violaceous border after a bite is cutaneous leishmaniasis, transmitted by the Phlebotomus sandfly (Leishmania tropica/L. major).
Discriminator: Painless chronic ulcer + violaceous border + bite history is the leishmaniasis vignette; the vector question follows.
| A) Anopheles mosquito | Anopheles mosquitoes transmit malaria. |
| B) Ixodes tick | Ixodes ticks transmit Lyme disease. |
| C) Culex mosquito | Culex mosquitoes transmit filariasis and West Nile virus. |
| D) Tsetse fly | Tsetse flies transmit African trypanosomiasis. |
Trap: Vector map — Phlebotomus sandfly is the leishmaniasis vector; it is the only one on the list.
Future alert: Leishmaniasis: painless ulcer + violaceous border + sandfly bite; vector = Phlebotomus.
Correct: A) To kill mites hatching from eggs present at the first application
Concept: Scabies — repeat application after 1 week to hit newly hatched mites Recall
Why A: Permethrin is repeated after one week because eggs survive the first application; the second dose kills mites hatching in the interim and prevents reinfestation.
Discriminator: The rationale for the scheduled repeat is the egg-hatch cycle — the stem asks exactly that.
| B) It is unnecessary — a single application always suffices | Guidelines mandate the repeat; single application leaves hatching eggs untreated. |
| C) To treat bacterial superinfection | Superinfection is treated separately with antibiotics, not extra scabicide. |
| D) To prevent post-scabetic itch | Post-scabetic itch persists 2-4 weeks and is hypersensitivity, not a reason to retreat. |
| E) Only needed if symptoms persist after four weeks | The repeat is scheduled at 1 week regardless of later symptoms. |
Trap: Mechanism of schedule — the 1-week repeat targets the egg-hatch cycle, not symptom persistence.
Future alert: Scabies: permethrin overnight, repeat after 1 week (egg hatch); treat all family members; itch may persist 2-4 weeks.
This MedCORE is not a medical textbook. It is only designed for rapid, last-minute recall and should be treated like a high-yield cheat sheet, not a complete learning resource. Use it to memorize critical algorithms and recognition patterns.