Neuronal intranuclear inclusion disease: recognition and update.

Area of Science:

• Neurology
• Genetics
• Pathology

Background:

• Neuronal intranuclear inclusion disease (NIID) was historically viewed as a neurodegenerative disease.
• Advances in skin biopsy diagnostics have significantly improved NIID detection rates.
• The disease is characterized by eosinophilic intranuclear inclusions in neural and other tissues.

Purpose of the Study:

• To update the understanding of NIID, including its discovery, clinical features, and diagnostic approaches.
• To review the genetic basis, specifically the NOTCH2NLC gene mutation, and its expanding spectrum of associated disorders.
• To provide new insights into the diagnosis and treatment of NIID based on recent findings and clinical experience.

Main Methods:

• Review of recent literature on NIID discovery milestones and genetic identification.
• Analysis of clinical phenotypes, including neurological and autonomic disturbances.
• Examination of laboratory findings and diagnostic advancements, such as skin biopsy and genetic testing.

Main Results:

• The GGC repeat expansion in the 5'-untranslated region of the NOTCH2NLC gene is identified as the causative mutation for NIID.
• This mutation is associated with a broad spectrum of neurological disorders beyond typical NIID phenotypes.
• The prevalence and ethnic distribution of the NOTCH2NLC expansion require further investigation, with current data suggesting a higher frequency in Asian populations.

Conclusions:

• NIID is a complex, multi-system degenerative disease with a recently elucidated genetic cause.
• The NOTCH2NLC gene expansion broadens the understanding of NIID and related disorders, necessitating further research into its full phenotypic spectrum.
• Continued research is crucial to refine diagnostic criteria and develop effective treatments for NIID and associated conditions.