Recent progress in neuronal intranuclear inclusion disease: a review of the literature.

To summarize the current understanding of neuronal intranuclear inclusion disease (NIID) and improve the understanding of the physician about this condition. We searched PubMed with keywords related to NIID and selected publications which seemed appropriate. We analyzed its clinical features, pathogenesis, evaluation methods, treatment options, and research prospectives. NIID is a degenerative condition which can affect multiple organ systems especially central nervous system. Its clinical features greatly vary, and making the exact diagnosis is often difficult. There are several genes which have been associated with this disorder. Some specific signs on diffusion-weighted-imaging (DWI) sequence of magnetic resonance (MR) imaging are characteristics to NIID. Intranuclear inclusions have been found in various nonneural cells of the body; therefore, the term systemic intranuclear inclusion disease is, perhaps, better suited to explain this disorder. There are several disorders which need to be ruled out before making the diagnosis, and neuroimaging and biopsy analysis should be combined to support the diagnosis.