[A case of neuronal intranuclear inclusion disease with coexisting Alzheimer's disease biomarker signature in cerebrospinal fluid].

The patient was a woman in her 70s who was admitted to the hospital for a evaluation due to complaints of forgetfulness and frequent falls. She was diagnosed with neuronal intranuclear inclusion disease (NIID) based on the high signal intensity at the corticomedullary junction on diffusion-weighted imaging (DWI) of the brain MRI, the presence of eosinophilic intranuclear inclusions on skin biopsy, GGC repeat expansion in the NOTCH2NLC gene, and her clinical symptoms. Despite the diagnosis of NIID, cerebrospinal fluid (CSF) biomarkers were positive for Alzheimer's disease (AD). Although cerebral blood flow SPECT did not show findings typical of AD, pathological involvement of both NIID and AD was suspected. Anticipating a rapid progression of cognitive decline, the early identification of these two neurodegenerative diseases was considered significant. CSF biomarkers for AD were found to be useful for understanding the complex underlying pathology in patients with cognitive impairment.