Objective: Here, we present three NIID cases. One of them, autopsy was performed.

Background: Neuronal intranuclear inclusion disease (NIID)(OMIM 603472) is a neurodegenerative disorder characterized by eosinophilic intranuclear inclusions in neuronal cells. Such inclusions are also found in non-neuronal cells. The clinical features and pathological findings in patients with NIID are highly varied.

Methods: Case 1 and 2 are adult onset NIID and case 3 is a juvenile onset. Case 1 is diagnosed as familial adult onset Parkinson’s disease with dementia, and case 2 is diagnosed as sporadic mild parkinsonism with dementia and psychosis. Case 3 is a juvenile onset familial case and diagnosed as oculopharyngeal muscular dystrophy (OPMD) with mental deterioration by muscle biopsy. Autopsy was performed after sudden death at age 42.

Results: In MRI imaging, diffuse cerebral atrophy was observed in all cases. High intensity of the cortico-medullary junction in diffusion-weighted imaging (DWI), which is characteristic findings in NIID, was seen in two adult onset cases. Ante-mortem diagnosis was made by identification of intranuclear inclusions with skin biopsy in two adult onset cases. Post-mortem diagnosis was made in juvenile case. In this case, acidophilic intranuclear inclusion body with positive p62 immune staining was observed, not only in neuron and glia cell, but all other organ tissues.

Conclusions: Intranuclear accumulation of abnormal proteins and/or dysfunction of protein degradation might underlie in the pathogenesis of NIID. However, NIID is considered as a heterogeneous disease entity and shows various clinical features. Not only neurologist, but also psychiatrist and pediatrician should pay attention to this heterogeneous disorder.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/three-cases-of-neuronal-intranuclear-inclusion-disease-niid/