[Sporadic adult-onset neuronal intranuclear inclusion disease with the main presentation of repeated cerebellar ataxia: a case study].

A 66-year-old woman suddenly experienced unsteadiness while walking; she had experienced the same symptom before, but it had resolved immediately. Her neurological findings showed cerebellar ataxia, absence of tendon reflex in the extremities, and orthostatic hypotension. MRI with DWI of the brain showed linear high-intensity areas at the white matter just below the cerebral cortex. Therefore, we suspected neuronal intranuclear inclusion disease (NIID). In her cutaneous skin biopsy, intranuclear inclusion bodies, which tested positive for an anti-ubiquitin antibody and anti-p62 antibody, were observed in sweat gland cells and fibroblasts; therefore, we diagnosed her with NIID. As no one in her family had similar symptoms, this was a case of sporadic NIID. Adult-onset NIID with the main presentation of cerebellar ataxia is rare; in our case, this repeated acute-onset symptom was a unique manifestation of the condition.