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Neuronal intranuclear inclusion disease (NIID) is a slowly progressive, neurodegenerative disease. NIID may affect any part of the nervous system (central, peripheral, and/or autonomic), as well as various organs.[14027] Signs and symptoms may begin anywhere from infancy to late adulthood, and can vary from person to person. In most cases, the disease begins in childhood.[14027]
Symptoms of NIID worsen over time and may include dementia, limb weakness, cerebellar ataxia, dystonia, parkinsonism, seizures, and autonomic dysfunction. Therefore, people with NIID may have impairment of balance, movement, cognition, communication, behavior, and the ability to function independently.[14027][14032] In general, limb weakness and ataxia are more common in children with NIID, while dementia is more common in people diagnosed in adulthood.[14027][14031]
The features of NIID result from the presence of eosinophilic intranuclear inclusions inside neurons and glial cells (abnormal masses of substances in the nuclei of cells of the nervous system).[14032][14027][14036] Recently, a genetic change in the NOTCH2NLC gene has been found to cause NIID.[15449]
Currently there is no treatment that cures or slows the progression of NIID, but medications that help control symptoms may improve quality of life.[14031] While the disease is ultimately fatal, life expectancy can range significantly, from one year to several decades after the diagnosis.[14027]
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