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Polymorphic Light Eruption — SCE Dermatology MCQ

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HardPhotobiologyPolymorphic Light EruptionSCE Dermatology

A woman develops a pruritic papulovesicular eruption 24 hours after the first substantial sun exposure each spring. It resolves without scarring and becomes less readily provoked later in summer. Which feature most strongly supports polymorphic light eruption over subacute cutaneous lupus?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: B — Seasonal reduction in provocation after repeated exposure, reflecting cutaneous hardening

Explanation lettering: E = shown as A · A = shown as E

B is correct. PLE commonly recurs after early-season exposure and may become less severe with repeated exposure as hardening develops; this phenomenon is also exploited by supervised pre-season phototherapy. Photosite distribution, delayed onset and benefit from photoprotection occur in several photodermatoses and are not specific. Annular or papulosquamous morphology can occur in cutaneous lupus, whereas PLE is morphologically variable but usually remains consistent within one patient. Continued sunlight should never be prescribed as unsupervised treatment, and lupus does not invariably worsen linearly throughout summer. The discriminating clue is therefore the reproducible early-season pattern followed by reduced provocation without scarring.

Reference: BAD polymorphic light eruption information: https://www.bad.org.uk/pils/polymorphic-light-eruption