🏥 USMLE Exam Prep

A 35-year-old male presents with recurrent episodes of acute abdominal pain, psychiatric disturbances, and dark urine after consuming alcohol and taking a new medication. Lab tests reveal elevated urinary porphobilinogen and delta-aminolevulinic acid. Which enzyme deficiency is most likely responsible for this patient's symptoms?

A Ferrochelatase
B Uroporphyrinogen decarboxylase
C Porphobilinogen deaminase (hydroxymethylbilane synthase)
D Coproporphyrinogen oxidase

✓ Correct Answer: Option C

The patient's symptoms (acute abdominal pain, neuropsychiatric issues, dark urine) and elevated porphobilinogen/delta-aminolevulinic acid are classic for Acute Intermittent Porphyria (AIP), which is caused by a deficiency in porphobilinogen deaminase (also known as hydroxymethylbilane synthase).

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