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Pseudoporphyria — SCE Dermatology MCQ

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HardDrug ReactionsPseudoporphyriaSCE Dermatology

A patient taking naproxen develops fragile photodistributed dorsal-hand bullae. Histology and immunofluorescence resemble porphyria cutanea tarda, but plasma, urine and faecal porphyrins are normal. What is the best interpretation?

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Correct answer: C — Diagnose pseudoporphyria, stop the culprit and use photoprotection with wound care

Explanation lettering: C = shown as A · D = shown as B · A = shown as C · B = shown as D

A is correct. Pseudoporphyria reproduces the photosensitive fragility, subepidermal blister and immunopathology of PCT but lacks biochemical porphyrin elevation. Drugs including naproxen and some diuretics, dialysis and intense UVA exposure are recognized associations. Management is withdrawal of the provoking factor when feasible, photoprotection and wound care. Venesection or hydroxychloroquine targets true porphyrin excess and is not justified by normal studies. EBA and bullous pemphigoid require appropriate serological, salt-split and clinicopathological correlation rather than being inferred from one shared finding.

Reference: Primary report: naproxen-induced pseudoporphyria: https://pubmed.ncbi.nlm.nih.gov/7777834/