Neuromuscular Disorders USMLE Step 1 Practice Question
A 7-month-old male presents with progressive weakness and profound hypotonia since 5 months of age. Vital signs: HR 120/min, RR 28/min, BP 85/55 mmHg, temperature 37°C, SpO2 98% on room air. Examination reveals absent deep tendon reflexes and preserved sensation. Serum creatine kinase is normal at 95 U/L. Genetic testing confirms degeneration of anterior horn cells. Which of the following mutations is most likely responsible for this neuromuscular disorder?
Answer choices
- ADystrophin frameshift mutation
- BCTG repeat expansion in DMPK
- CDystrophin in frame mutation
- DPMP22 duplication
- ESMN1 deletionCorrect answer
- FCHRNA1 missense mutation
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