Abstract Background Spinocerebellar ataxia type 31 (SCA31) is not usually associated with dementia, and autopsy in a patient with both conditions is very rare. Case presentation An 87-year-old male patient presented with ataxia and progressive dementia. Genetic testing led to a diagnosis of SCA31. Fifteen years after his initial symptoms of hearing loss and difficulty walking, he died of aspiration pneumonia. A pathological analysis showed cerebellar degeneration consistent with SCA31 and abundant argyrophilic grains in the hippocampal formation and amygdala that could explain his dementia. Conclusions This is the first autopsy report on comorbid argyrophilic grain disease with SCA31.
