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Pityriasis rubra pilaris — SCE Dermatology MCQ

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HardGeneral dermatology & dermatology in primary health carePityriasis rubra pilarisSCE Dermatology

A 68-year-old with new erythroderma has orange-red colour, islands of sparing, follicular hyperkeratosis and waxy palmoplantar keratoderma. Two biopsies are only partially supportive of pityriasis rubra pilaris, and he has lymphadenopathy. What must be actively excluded?

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Correct answer: A — Erythrodermic cutaneous T-cell lymphoma, including Sezary syndrome

Explanation lettering: E = shown as B · B = shown as D · D = shown as E

A is correct. The morphology suggests PRP, but adult erythroderma is a reaction pattern and clinicopathological discordance plus lymphadenopathy requires exclusion of cutaneous T-cell lymphoma or Sezary syndrome. Assessment may require repeat biopsies, blood film and flow cytometry, T-cell receptor studies and nodal evaluation in the appropriate multidisciplinary pathway. Miliaria, molluscum, seborrhoeic keratoses and localised candidal intertrigo do not plausibly produce this chronic whole-skin syndrome. Islands of sparing are supportive of PRP but not pathognomonic, and treatment should not proceed as if morphology alone has excluded malignancy.

Reference: DermNet erythroderma: https://dermnetnz.org/cme/emergencies/erythroderma