Background: Machado-Joseph disease (MJD; spinocerebellar ataxia type 3) is a hereditary neurodegenerative disease caused by mutation of the MJD1 gene. Patients with MJD usually present with cerebellar ataxia, external ophthalmoplegia, pyramidal and extrapyramidal signs, and muscle wasting. However, it has been reported that these patients do not demonstrate dementia.
Case description: We noticed symptoms of dementia and delirium in 4 patients with MJD. The symptoms included abnormal behavior, excitation, an uncooperative attitude, crying, disorientation, slow thought processes, hallucinations, and delusions. These symptoms were observed in patients with a relatively young onset age, and after a long clinical course. In these patients, the CAG repeat length in the MJD1 gene was much longer compared with the mean repeat length found in patients with MJD. On electroencephalographical examination, they showed slow background activity, but computed tomography and magnetic resonance imaging scans showed no cerebrocortical atrophy. Neuropathological findings in 2 patients revealed a normal cortical structure on conventional morphological examination, but at immunohistochemical examination, we found abnormal staining by an antipolyglutamine antibody in the cerebrocortical neuronal nuclei.
Conclusions: Symptoms of dementia and delirium in patients with MJD could occur in the late stages, and they might be caused not by loss of cerebrocortical neurons, but by their dysfunction.