Neurodegenerative Diseases USMLE Step 1 Practice Question
A 4 year old boy is brought to clinic because of frequent falls and difficulty climbing stairs. Examination shows proximal lower extremity weakness, enlarged calves, and use of his hands to rise from the floor. Serum creatine kinase is markedly elevated. Which of the following is the most likely underlying defect?
Answer choices
- APostsynaptic acetylcholine receptor antibodies
- BExpansion of CTG repeats in the DMPK gene
- CMutation in the chloride channel of skeletal muscle
- DDeletion causing frameshift mutation in the dystrophin geneCorrect answer
- EMutation in the ryanodine receptor causing malignant hyperthermia
- FNonsense mutation in the dystrophin gene creating a premature stop codon
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.