[Neuronal intranuclear inclusion disease (NIID)]

Neuronal intranuclear inclusion disease (NIID) is a progressive neurodegenerative disease that had been diagnosed by autopsy until recently, but the number of cases has increased since skin biopsy was reported to be useful in 2011. In 2019, the genetical cause of NIID was identified as the extension of the GGC repeat sequence on the NOTCH2NLC gene, and genetic diagnosis became possible. In NIID, there are two groups: a group onset with cognitive dysfunction, and with leukoencephalopathy on head MRI and a high intensity signal at the corticomedurally junction on DWI, and a group with limb weakness. It is necessary to include NIID in the differential diagnosis of leukoencephalopathy and neuropathy, and it is necessary to combine skin biopsy and genetic testing to accurately diagnose of NIID and promote pathological elucidation.