Neuronal intranuclear inclusion disease with subclinical peripheral neuropathy: A case report

Neuronal intranuclear inclusion disease (NIID) is a slowly progressing neurodegenerative disease with various manifestations and high heterogeneity. Clinical characteristics, imaging, skin biopsy, and genetic testing are necessary for its diagnosis. Electromyography may also be a useful tool for diagnosing NIID. In this study, we report a patient with motor and sensory nerve demyelination changes accompanied by axonal damage.

A 64-year-old woman was admitted to our department with gradually worsening forgetfulness for over a year. After 6 years of follow-up, the symptoms progressively deteriorated.

Cerebrospinal fluid analysis revealed increased protein levels. Brain magnetic resonance imaging showed characteristic "ribbon-like" high signals in the corticomedullary junction area on diffusion-weighted imaging. High-intensity signals in the white matter were also observed on T2 and fluid-attenuated inversion recovery imaging. Electromyography revealed multiple peripheral nerve damage and conduction changes, including motor and sensory nerve demyelination changes, accompanied by axonal damage. Skin biopsy revealed inclusion bodies with strong positive staining for P62 and ubiquitin antibodies in the nuclei of sweat gland cells, adipocytes, and fibroblasts. Genetic testing indicated that the number of GGC repeats in NOTCH2NLC alleles were 14 and 134, respectively. Consequently, the patient was diagnosed with NIID.

Currently, no effective treatment is available to delay the progression of the disease.

We report a case of NIID with subclinical peripheral neuropathy, although the patient did not experience sensory symptoms such as numbness in the extremities. Electromyography can be used to detect subclinical peripheral nerve damage.