Presenile onset of spinocerebellar ataxia type 1 presenting with conspicuous psychiatric symptoms and widespread anti‐expanded polyglutamine antibody‐ and fused in sarcoma antibody‐immunopositive pathology

A 50‐year‐old Japanese man showed slowly progressive gait disturbance and dysarthria. Neurological examination 5 years after onset revealed slow eye movement with nystagmus as well as limb and truncal ataxia. Magnetic resonance imaging showed atrophy of the cerebellum and brainstem. Because genetic examination revealed CAG repeat expansion of the ataxin‐1 gene, the patient was diagnosed with spinocerebellar ataxia type 1. Ten years after onset, he showed psychiatric symptoms with cognitive impairment, and antipsychotic drugs were administered. As psychiatric symptoms gradually worsened, particularly with regard to resisting nursing care and shouting, the doses of the drugs were increased. Although the clinicopathologic findings were generally identical to previously reported spinocerebellar ataxia type 1 cases with the exception of the conspicuous psychiatric symptoms, there are two notable immunohistochemical findings. Firstly, numerous anti‐expanded polyglutamine antibody‐immunopositive neuronal inclusions were extensively observed, including in the cerebral cortex and limbic system, but not in the Purkinje cells. Secondly, anti‐fused in sarcoma antibody‐immunopositive intranuclear inclusions were extensively observed. We posit that the anti‐expanded polyglutamine antibody‐immunopositive neuronal inclusions and possibly the anti‐fused in sarcoma antibody‐immunopositive inclusions, particularly those in the neocortex and limbic system, may correspond to the psychiatric symptoms and cognitive impairment that were observed in the patient.