Metabolism USMLE Step 1 Practice Question
A 7-month-old infant presents with lethargy, seizures, and rapid breathing following an overnight fast during a viral illness. Vital signs show HR 128/min, RR 32/min, BP 90/58 mmHg, temperature 38.2°C. Laboratory studies reveal blood glucose 35 mg/dL, venous pH 7.22 with lactate 8.2 mmol/L, and elevated ketones. Serum ammonia and liver transaminases are normal. Physical examination reveals no hepatomegaly. Deficiency of which enzyme most likely explains these findings?
Answer choices
- AGlucose 6 phosphatase
- BGalactokinase
- CFructose 1,6 bisphosphataseCorrect answer
- DPyruvate kinase
- EBranching enzyme
- FMedium chain acyl-CoA dehydrogenase (MCAD)
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