Neurodegenerative Diseases USMLE Step 1 Practice Question
A 42 year old man is evaluated for involuntary movements and personality change. His father died in his early 50s after progressive dementia. Examination shows choreiform movements and impaired saccadic eye movements. MRI demonstrates atrophy of the caudate nuclei with enlargement of the lateral ventricles. Which of the following best describes the genetic basis of this disorder?
Answer choices
- APaternal uniparental disomy of chromosome 15
- BAutosomal recessive CTG trinucleotide repeat expansion
- CAutosomal dominant CAG trinucleotide repeat expansion with anticipationCorrect answer
- DX linked mutation in dystrophin
- EMitochondrial mutation affecting oxidative phosphorylation
- FAutosomal dominant polyglutamine expansion in the ATXN3 gene (spinocerebellar ataxia type 3)
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.