Porphyria cutanea tarda (PCT) is the most common porphyria. The deficient enzyme causes cutaneous blistering in sun-exposed areas but NO neurological symptoms. Which drug is a classical precipitant of symptomatic PCT?
- A Chloroquine (at low doses) ✓
- B Phenobarbital
- C Succinylcholine
- D Rifampicin
Correct answer: A. Chloroquine (at low doses)
Explanation
PCT is caused by deficiency of uroporphyrinogen decarboxylase (UROD). Uroporphyrinogen I accumulates and is oxidized to uroporphyrin I, which causes photosensitivity and blistering. Precipitants include alcohol, hepatitis C, HIV, estrogens, and chloroquine. At low doses (not the high doses used for malaria/lupus), chloroquine mobilizes porphyrins from the liver, worsening PCT acutely. Treatment is phlebotomy (to reduce hepatic iron) or low-dose chloroquine (paradoxically used therapeutically at controlled doses). Phenobarbital precipitates AIP (not PCT).
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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