Dermatology confusion pairs
9 Dermatology topics students commonly mix up on Step 2 CK, each with the fastest separator, a side-by-side comparison, and a free practice question.
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- Bullous pemphigoid vs Pemphigus vulgarisPresence of mucosal erosions with flaccid bullae is the fastest discriminator for pemphigus vulgaris.
- Stevens-Johnson syndrome vs Toxic epidermal necrolysisPercent body surface area detached is the key discriminator, below 10 percent for SJS and above 30 percent for TEN.
- Eczema vs PsoriasisFlexural intensely pruritic dermatitis favors eczema, while extensor sharply demarcated silvery plaques favor psoriasis.
- Erythema multiforme vs SJS/TENMucosal erosions with epidermal detachment after a high-risk drug indicate SJS/TEN rather than erythema multiforme.
- Melanoma vs Seborrheic keratosisEvolution in size, shape, or color is the highest-yield discriminator favoring melanoma over seborrheic keratosis.
- DRESS vs SJSMucosal erosions with epidermal detachment identify SJS rather than DRESS.
- Squamous cell carcinoma vs Basal cell carcinomaA pearly papule with rolled border and telangiectasias points to basal cell carcinoma.
- Cellulitis vs Stasis dermatitisBilateral chronic hyperpigmented pruritic edema favors stasis dermatitis, while acute unilateral tenderness favors cellulitis.
- Tinea versicolor vs VitiligoPresence of fine scale with positive KOH fungal elements distinguishes tinea versicolor from vitiligo.