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Pityriasis Rosea — SCE Dermatology MCQ

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EasyInflammatory DermatosesPityriasis RoseaSCE Dermatology

A 29-year-old woman presents with a well-demarcated salmon-pink plaque with fine collarette of scale (described as 'herald patch') on her trunk. Two weeks later, she develops multiple smaller ovoid pink patches distributed along skin cleavage lines in a 'Christmas tree' pattern. What is the most likely diagnosis?

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Correct answer: B — Pityriasis rosea

Pityriasis rosea classically presents with a herald patch (a single larger plaque, often misdiagnosed as tinea) followed 1-2 weeks later by a secondary eruption of smaller ovoid patches aligned along Langer lines (Christmas tree pattern on the back). It is thought to be associated with HHV-6 and HHV-7 reactivation. The condition is self-limiting, resolving within 6-12 weeks. Syphilis serology should be performed to exclude secondary syphilis, which can mimic pityriasis rosea. Treatment is symptomatic with emollients and moderate topical corticosteroids if pruritic.

Reference: BAD 2019 Patient Information on Pityriasis Rosea