Erythema multiforme: The Daily PANCE Blueprint
A 22-year-old college student presents to the clinic after noticing strange “bullseye” spots popping up on his palms and forearms. He says they started shortly after a cold sore breakout and are not itchy, but feel a little sore. He denies any new medications, no mucosal involvement, and feels otherwise well. What is the most likely diagnosis?
A. Erythema multiforme
B. Stevens-Johnson syndrome
C. Urticaria
D. Contact dermatitis
E. Bullous pemphigoid
Answer and topic summary
The answer is A. Erythema multiforme
Erythema multiforme (EM) is a hypersensitivity reaction often triggered by herpes simplex virus (HSV) infection. It presents with targetoid (target-shaped) lesions, commonly on palms, soles, and extensor surfaces. These lesions are symmetric, well-demarcated, and may appear in successive “crops.” EM is self-limited, and unlike Stevens-Johnson syndrome (SJS), it lacks mucosal involvement and systemic symptoms.
HSV is the most common infectious trigger, but medications like sulfa drugs and penicillin can also be associated.
Incorrect answer explanations:
- Stevens-Johnson syndrome – A more severe mucocutaneous reaction often drug-induced; involves widespread skin sloughing and painful mucosal erosions, which are absent in this case.
- Urticaria – Presents as transient wheals (hives) that are pruritic, not fixed target lesions, and unrelated to HSV.
- Contact dermatitis – Itchy, eczematous rash confined to areas of allergen exposure; no target lesions.
- Bullous pemphigoid – Occurs in older adults, features tense blisters, not target lesions, and no link to HSV.
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Smarty PANCE Content Blueprint Review:
Covered under ⇒ PANCE Blueprint Dermatology ⇒ ⇒
Also covered on the Family Medicine EOR and Pediatric PAEA rotation content topic list
