Metabolism USMLE Step 1 Practice Question
A 23-year-old woman presents with severe colicky abdominal pain, anxiety, and dark reddish urine three days after initiating phenobarbital for insomnia. Vital signs show HR 118/min, BP 142/88 mmHg, RR 20/min, temperature 37.2°C. Physical examination reveals tachycardia but no acute skin lesions or neurological deficits. Urinalysis demonstrates dark urine with elevated porphobilinogen. Serum electrolytes are normal. Deficiency of which enzyme most likely explains these findings?
Answer choices
- AALA dehydratase
- BFerrochelatase
- CBiliverdin reductase
- DUroporphyrinogen decarboxylase
- EPorphobilinogen deaminaseCorrect answer
- FCoproporphyrinogen oxidase
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