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18-Year-Old Male with Widespread Targetoid Rash

Can you diagnose this case?

David L. Kaplan, MDSeries Editor

Signs and Symptoms

This 18-year-old young man had been exposed to poison ivy 2 weeks previously and had developed Rhus allergic contact dermatitis on his legs that had responded to potent topical corticosteroids. He now presented with a few-day history of circular lesions on his hands, trunk, and extremities (with sparing of the mucous membranes) that he described as itchy and tender. He was otherwise healthy, and he denied any new medications and any recent upper respiratory infections or fever blisters.

What explains this man’s widespread targetoid rash?

Choose one to reveal diagnosis and discussion

Rebound allergic contact dermatitis
Urticaria
Erythema multiforme
New contact dermatitis from a different allergen
Measles

ANSWER: Erythema multiforme induced by poison ivy

See the full case at Consultant360

Rhus allergic contact dermatitis–induced erythema multiforme (EM) is an underreported but well-documented occurrence.1,2 Fortunately, this condition usually responds to treatment with systemic corticosteroids.

Urticaria tends to come and go, unlike these lesions, which have been present for a few days. There was no history of contact dermatitis, and the target-like lesions are characteristic of EM, not contact dermatitis. Measles starts with fever, runny nose, cough, red eyes, and sore throat, followed by a rash that spreads over the body with accompanying oral lesions, unlike what is seen in this patient’s case.

References
    1. Werchniak AE, Schwarzenberger K. Poison ivy: an underreported cause of erythema multiforme. J Am Acad Dermatol. 2004;51(5 suppl):S159-S160.
    2. Cohen LM, Cohen JL. Erythema multiforme associated with contact dermatitis to poison ivy: three cases and a review of the literature. Cutis. 1998;62(3):139-142.

David L. Kaplan, MD, is a clinical assistant professor of dermatology at the University of Missouri–Kansas City School of Medicine in Kansas City, Missouri, and at the University of Kansas School of Medicine in Kansas City, Kansas. He practices adult and pediatric dermatology in Overland Park, Kansas.