Case Review: An unusual presentation of amyotrophic lateral sclerosis-like symptoms in confirmed adult-onset neuronal intranuclear inclusion disease

Background: Neuronal intranuclear inclusion disease (NIID) is defined via the presence of histopathologic eosinophilic hyaline intranuclear inclusion within not only the central and peripheral nervous system, but also the autonomic system as well as several visceral organs and dermal cells. The presence of these intranuclear inclusions produces a gradually progressive neurodegenerative disease characterized by a GGC repeat in the 5’ end of the Notch 2 N-terminal like C ( NOTCH2NCL ) gene. The primary types of clinical manifestation of NIID are exhibited by muscle weakness, dementia, and parkinsonism type. With NIID attaining a high heterogeneity in terms of clinical presentation, it is often easily misdiagnosed with other diseases including amyotrophic lateral sclerosis (ALS). Similar to NIID, ALS may also arise through the mutation of the NOTCH2NCL gene, leading to an extended GGC repeat and can coexist with NIID as reported by two cases. With this being mentioned, it can be hypothesized that ALS may contribute to a special phenotype of NIID and may attain comparable clinical attributes upon clinical diagnosis. Case presentation: In this case review, although the clinical presentation was highly indicative towards ALS, the patient was confirmed NIID via genetic analysis and skin biopsy. This can be further attributed to the absence of sensory and autonomic nerve impairment during the preliminary manifestation, and physical examination with upper motor neuron signs as well as the lack of hyper-intensive signals in the corticomedullary junctions in DWI. Conclusion: This review aims to provide insights towards the differential diagnosis of NIID with diseases exhibiting similar manifestation such as ALS.