Porphyria cutanea tarda (PCT) is characterised by skin photosensitivity and blistering. The enzyme deficient is:

• A Uroporphyrinogen decarboxylase (UROD) ✓
• B Ferrochelatase
• C ALA dehydratase
• D Coproporphyrinogen oxidase

Explanation

PCT results from UROD deficiency (acquired most commonly, or autosomal dominant inherited), causing uroporphyrinogen accumulation; uroporphyrins absorb light and generate reactive oxygen species in the skin, causing photosensitivity, subepidermal blistering, and skin fragility. Ferrochelatase deficiency causes erythropoietic protoporphyria (burning pain without blistering). ALA dehydratase deficiency causes porphyria with neurovisceral attacks. Coproporphyrinogen oxidase deficiency causes hereditary coproporphyria.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.