Metabolism USMLE Step 1 Practice Question
A 46 year old man presents with chronic back pain and dark staining of his underwear. He reports that his urine turns black if left standing in the toilet. Physical examination reveals bluish black discoloration of the ear cartilage and sclerae. Which of the following enzyme deficiencies is the most likely cause of this disorder?
Answer choices
- ADopamine beta hydroxylase
- BHomogentisate oxidaseCorrect answer
- CBranched chain alpha ketoacid dehydrogenase
- DTyrosinase
- EPhenylalanine hydroxylase
- FATP7B (Wilson disease)
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