Movement Disorders USMLE Step 1 Practice Question
A 28-year-old man with no prior psychiatric history presents with acute-onset chorea, compulsive behaviors, and emotional lability three weeks after group A streptococcal pharyngitis. Vital signs: BP 118/76, HR 92, RR 16, Temp 37.2°C, SpO2 98%. Laboratory studies show elevated anti-DNase B titers. Echocardiography reveals no valvular disease. He denies recent cocaine use. Which pathophysiologic mechanism best explains his neuropsychiatric syndrome?
Answer choices
- ADopamine depletion from streptococcal toxins
- BAutoimmune demyelination of motor tracts
- CViral reactivation in the substantia nigra
- DDirect bacterial invasion of the striatum
- EMolecular mimicry causing anti-basal ganglia antibodiesCorrect answer
- FExcitotoxic damage from glutamate released by activated microglia
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