A 40-year-old man of South African descent presents with recurrent acute abdominal pain and neuropathy, and separately complains of painful blistering lesions on sun-exposed skin. Plasma shows fluorescence at 626 nm on excitation. The most likely enzyme defect is:
- A Coproporphyrinogen oxidase
- B Protoporphyrinogen oxidase ✓
- C Uroporphyrinogen decarboxylase
- D Ferrochelatase
Correct answer: B. Protoporphyrinogen oxidase
Explanation
Variegate porphyria results from protoporphyrinogen oxidase deficiency and uniquely combines neurovisceral attacks with cutaneous photosensitivity. It is highly prevalent among South Africans due to a founder mutation, and plasma fluorescence at 626 nm is its diagnostic signature. Hereditary coproporphyria (option A) also shows both features, but lacks the founder association and the characteristic plasma peak, while PCT and EPP cause no neuropsychiatric attacks.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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