Neuromuscular Disorders USMLE Step 1 Practice Question
A 34-year-old man presents with difficulty releasing his grip after handshaking. He reports early frontal balding and recent cataracts. Vital signs are stable: BP 128/82, HR 78, RR 16, Temp 37°C, SpO2 98%. Physical examination reveals myotonia. Laboratory studies show elevated creatine kinase at 850 IU/L. He denies recent medication use or muscle pain. Which of the following is the most likely diagnosis?
Answer choices
- ADermatomyositis
- BMyotonic dystrophyCorrect answer
- CDuchenne muscular dystrophy
- DLambert-Eaton syndrome
- EPolymyalgia rheumatica
- FGlycogen storage disease type V (McArdle disease)
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.