A 40-year-old woman on long-term chloroquine for discoid lupus develops bullous lesions on sun-exposed areas with milia formation and scarring. Urine turns pink-red after sun exposure. Biochemical testing confirms elevated urinary and plasma porphyrins. This drug-induced condition mimics which primary blistering disorder?

• A Pemphigus vulgaris
• B Epidermolysis bullosa acquisita
• C Porphyria cutanea tarda ✓
• D Bullous systemic lupus erythematosus

Explanation

Porphyria cutanea tarda (PCT) presents with fragile, sub-epidermal blisters on sun-exposed skin (dorsa of hands and face), milia, hypertrichosis of the malar area, and hyperpigmentation. Urine shows coral-pink fluorescence under Wood's lamp due to excess uroporphyrins. Chloroquine in low doses is actually used to treat PCT (by mobilising hepatic porphyrins), but in this scenario, the drug exacerbated an underlying predisposition. PCT is caused by deficiency of uroporphyrinogen decarboxylase. Key differentiator: type VII collagen auto-antibodies and DIF deposits at DEJ distinguish EBA, which can clinically mimic PCT.

Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.