Neuromuscular Disorders USMLE Step 1 Practice Question
A 3-month-old male infant presents with poor feeding and generalized hypotonia for 2 weeks. Vital signs show HR 145/min, RR 32/min, BP 78/52 mmHg, and normal temperature. Physical examination reveals macroglossia, cardiomegaly on chest X-ray, and hepatomegaly. Serum creatine kinase is elevated at 850 U/L. The infant has no respiratory distress or seizure activity. Which enzyme deficiency most likely explains these findings?
Answer choices
- ABranching enzyme
- BMyophosphorylase kinase
- CLysosomal acid alpha glucosidaseCorrect answer
- DMuscle glycogen phosphorylase
- EDebranching enzyme
- FAcid maltase
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