Objective: Huntington’s disease (HD) is an autosomal dominant neurodegenerative disorder caused by CAG repeat expansion in the HTT gene, typically presenting in midlife with chorea, cognitive decline, and psychiatric symptoms.

Background: However, late-onset HD, defined as onset after age 60, may occur, particularly in patients with relatively smaller CAG repeat expansions. Late-onset HD often progresses slowly and may initially present with focal or asymmetric chorea, leading to misdiagnosis as post-stroke chorea or other secondary movement disorders. Reports of late-onset HD initially misdiagnosed as post-stroke chorea remain limited.

Method: A 78-year-old woman was referred to the neurology outpatient clinic for evaluation of abnormal facial movements and mild limb weakness.

Results: One month earlier, brain MRI at a local medical center revealed acute infarction in the right lenticulostriate artery territory, and she was diagnosed with oromandibular dyskinesia associated with stroke. She received standard medical therapy for stroke and haloperidol for symptomatic control. Her medical history included hypertension, diabetes mellitus, and hyperlipidemia. There was no family history of movement disorders, and no exposure to medications known to cause abnormal movements. Neurological examination showed mild dysarthria, left-sided weakness, and choreic movements involving the left extremities and orofacial region. The onset of the abnormal movements was unclear and did not markedly worsen immediately after the stroke. One year later, chorea appeared in the right extremities, and over the following two years it progressively involved the entire body. The patient also developed progressive cognitive decline. Initial cognitive testing showed a Mini-Mental State Examination (MMSE) score of 17 and a Global Deterioration Scale (GDS) score of 3, which deteriorated three years later to MMSE 9, GDS 5. Given the progressive course, genetic testing for HD was performed, identifying 40 CAG repeats in the HTT gene, confirming the diagnosis of late-onset Huntington’s disease.

Conclusion: Post-stroke chorea usually occurs acutely and often improves over time, whereas Huntington’s disease is progressive. Careful longitudinal observation and timely genetic testing are essential for differentiating late-onset HD from post-stroke chorea.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/late-onset-huntingtons-disease-misdiagnosed-as-post-stroke-chorea-a-case-report/