A 41-year-old man is brought to the clinic by his sister because of progressive behavioral changes and abnormal movements over the past year. She reports that he has become increasingly irritable, has difficulty concentrating at work, and has made several inappropriate comments in social settings. Over the past 6 months, he has developed frequent involuntary, jerky movements of his hands and face that worsen with stress. Review of systems is notable for unintentional weight loss and insomnia. He denies headaches, seizures, or visual disturbances. Past medical history is unremarkable. He takes no medications. Family history is significant for a father who died in his early 50s after a long course of progressive dementia and movement abnormalities. The patient does not smoke and drinks alcohol socially. Vital signs are within normal limits. On physical examination, the patient is alert but has impaired attention and executive function. Neurologic examination reveals choreiform movements of the upper extremities and facial grimacing. MRI of the brain shows bilateral atrophy of the caudate nucleus.
D) Huntington disease
Huntington disease is an autosomal dominant neurodegenerative disorder caused by CAG trinucleotide repeat expansion in the HTT gene on chromosome 4. It is characterized by progressive chorea, psychiatric disturbances, and cognitive decline, typically beginning in mid-adulthood. Neurodegeneration primarily affects the caudate nucleus and putamen, leading to the characteristic MRI finding of caudate atrophy. The family history of a similarly affected parent strongly supports this diagnosis.
Answer choice A: Alzheimer disease, is incorrect. Alzheimer disease presents with gradual memory impairment and cognitive decline, typically without prominent movement disorders such as chorea. MRI findings involve cortical and hippocampal atrophy rather than caudate nucleus degeneration.
Answer choice B: Creutzfeldt-Jakob disease, is incorrect. Creutzfeldt-Jakob disease causes rapidly progressive dementia over weeks to months, often with myoclonus and characteristic electroencephalogram (EEG) and MRI findings. It does not present with a long prodrome of psychiatric symptoms or chorea.
Answer choice C: Dementia with Lewy bodies, is incorrect. Dementia with Lewy bodies is characterized by fluctuating cognition, visual hallucinations, rapid eye movement (REM) sleep behavior disorder, and parkinsonism. Chorea and caudate atrophy are not typical features.
Answer choice E: Wilson disease, is incorrect. Wilson disease presents with hepatic dysfunction, psychiatric symptoms, and movement disorders due to copper accumulation. It typically occurs in younger patients and is associated with Kayser-Fleischer rings on physical examination of the eyes and abnormal copper studies, which are not described here.
Key Learning Point
Huntington disease is an autosomal dominant disorder caused by CAG repeat expansion that leads to caudate nucleus degeneration, resulting in chorea, psychiatric symptoms, and progressive cognitive decline.
