Late-Onset Huntington's Disease: A Case Report and Literature Review.

Huntington's disease (HD) is a rare autosomal dominant neurodegenerative disorder caused by expansion of the cytosine-adenine-guanine (CAG) trinucleotide repeat in the huntingtin (HTT) gene. Although the disease typically presents in mid-adulthood, symptom onset after the age of 60, defined as late-onset Huntington's disease (LoHD), remains uncommon and may pose diagnostic challenges. We report the case of an 80-year-old man admitted for evaluation of progressive unintentional weight loss, whose clinical assessment revealed generalized chorea and progressive cognitive decline. Genetic testing identified an expanded CAG allele with 39 repeats, confirming the diagnosis of LoHD. Neuroimaging revealed ischemic leukoencephalopathy consistent with cerebral small vessel disease (CSVD), contributing to diagnostic complexity. This case highlights the importance of considering Huntington's disease in the differential diagnosis of late-onset chorea and cognitive impairment, even in the absence of a known family history.