Polymorphic light eruption

Diagnosis: Polymorphic light eruption

Clinical Presentation

Polymorphic light eruption

Clinical History

Recurrent pruritic eruption on sun-exposed skin in spring/early summer. Improves with repeated exposure. Consistent morphology per patient.

Treatment

Sun protection (broad-spectrum UVA/UVB sunscreen). Prophylactic phototherapy in spring (NB-UVB, PUVA). Topical corticosteroids. Oral: short course prednisone, hydroxychloroquine, nicotinamide.

Differential Diagnosis

• Lupus erythematosus • Solar urticaria • Photoallergic drug eruption • Erythema multiforme • Actinic prurigo • Porphyria

Key Learnings

• Most common photodermatosis — pruritic papules/plaques on sun-exposed skin in spring/early summer • "Hardening" phenomenon: lesions improve with repeated sun exposure as summer progresses • Consistent morphology within individual patients but polymorphic between patients • Delayed onset: hours to days after UV exposure (distinguishes from solar urticaria) • More common in fair-skinned, females, and in northern latitudes • Photoprotection and controlled phototherapy ("desensitization") before summer are effective

Tags: dermatologist, dermatology, kodachrome, Polymorphic light eruption