Hereditary coproporphyria (HCP) is an acute hepatic porphyria with both neurovisceral attacks and, variably, cutaneous photosynthesis. Which enzyme is deficient?
- A Uroporphyrinogen decarboxylase
- B Protoporphyrinogen oxidase
- C Coproporphyrinogen oxidase ✓
- D Porphobilinogen deaminase
Correct answer: C. Coproporphyrinogen oxidase
Explanation
Hereditary coproporphyria results from deficiency of coproporphyrinogen oxidase, the sixth step of heme synthesis. Coproporphyrinogen III accumulates and is oxidized to coproporphyrin. Unlike AIP, HCP can also present with skin photosensitivity because the accumulated porphyrin is photosensitising. Variegate porphyria involves the next enzyme, protoporphyrinogen oxidase.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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