[A case of spinocerebellar ataxia 6 accompanied with schizophrenia]

An abnormally expanded CAG repeats (25, normal; 4-20) was identified in the alpha 1A voltage-dependent calcium channel (CACNA1A) gene of a 50-year-old Japanese man with 25 years history of schizophrenia. At age 45, he first noted unsteadiness of standing and gait, which gradually worsened subsequently. In addition to the psychiatric symptoms of schizophrenia, neurological examination revealed marked truncal ataxia and mild limb ataxia. Brain magnetic resonance imaging showed atrophy of the cerebellar vermis. Gene analysis confirmed the diagnosis of spinocerebellar ataxia type 6 (SCA 6). No family members showed similar neuropsychiatric symptoms except that the patient's father had been suffering from an unknown dementing disease. Occurrence of both schizophrenia and SCA 6 in the identical patient may be coincidental. However, growing evidence has shown that various mutations in the CACNA1A gene are associated with phenotypic variability, such as progressive ataxia, episodic ataxia, migraine, coma, epilepsy and mental retardation. Therefore, the schizophrenic symptoms, association of which with SCA 6 has previously reported in a few cases, may represent rare clinical features of the channelopathy associated with the mutation in the CACNA1A gene.