Metabolism USMLE Step 1 Practice Question
A 49-year-old man with chronic hepatitis C presents with fragile skin and blistering lesions on the dorsal hands worsening with sun exposure. Vital signs: BP 128/82, HR 88, RR 16, Temp 37.2°C, SpO2 98%. He reports dark urine and reports no abdominal pain or psychiatric symptoms. Laboratory studies show elevated transaminases and urine porphobilinogen level within normal limits. Which enzyme is most likely deficient?
Answer choices
- AFerrochelatase
- BALA synthase
- CProtoporphyrinogen oxidase
- DUroporphyrinogen decarboxylaseCorrect answer
- EPorphobilinogen deaminase
- FCoproporphyrinogen oxidase
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