A 25-year-old asymptomatic woman is evaluated after her 28-year-old brother is diagnosed with Wilson's disease. Serum ceruloplasmin is 18 mg/dL (low-normal), liver enzymes are normal, and slit-lamp examination shows no Kayser-Fleischer rings. Which is the most appropriate next step to confirm or exclude Wilson's disease in this sibling?
- A Hepatic copper quantification on liver biopsy ✓
- B 24-hour urinary copper excretion
- C Genetic testing for ATP7B mutations
- D Serial monitoring of liver enzymes annually
Correct answer: A. Hepatic copper quantification on liver biopsy
Explanation
First-degree relatives of Wilson's disease patients require systematic screening. When ceruloplasmin is equivocal and K-F rings are absent, hepatic copper quantification (>250 µg/g dry weight) is the gold standard for diagnosis in asymptomatic siblings. 24-hour urinary copper alone can be equivocal in asymptomatic carriers. Genetic testing is confirmatory but requires identifying the specific ATP7A mutations in the index patient first. Observation without definitive testing is inappropriate given the availability of effective treatment.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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