We report a case of neuronal intranuclear inclusion disease (NIID) confirmed by detection of intranuclear inclusions in a skin biopsy specimen. Brain magnetic resonance imaging showed mild cerebral atrophy and linear hyperintensities at the corticomedullary junction on diffusion-weighted images. This patient developed nonconvulsive status epilepticus with generalized periodic discharges on electroencephalography after recurrent symptoms of paroxysmal nausea and slowly progressive cognitive decline. There have been no previous reports of NIID with nonconvulsive status epilepticus to our knowledge. Since adult patients with NIID display a wide variety of clinical manifestations, skin biopsy should be considered in patients who have leukoencephalopathy of unknown origin.