Neuronal intermediate filament inclusion disease (NIFID) is a frontotemporal lobar degeneration (FTLD) characterized by frontotemporal dementia (FTD), pyramidal and extrapyramidal signs. The disease is histologically characterized by the presence of abnormal neuronal cytoplasmic inclusions (NCIs) which contain α-internexin and other neuronal intermediate filament (IF) proteins. Gigaxonin (GAN) is a cytoskeletal regulating protein and the genetic cause of giant axonal neuropathy. Since the immunoreactive profile of NCIs in NIFID is similar to that observed in brain sections from Gan(Δex1/Δex1) mice, we speculated that GAN could be a candidate gene causing NIFID. Therefore, we performed a mutation analysis of GAN in NIFID patients. Although the NCIs of NIFID and Gan(Δex1/Δex1) mice were immunohistochemically similar, no GAN variant was identified in DNA obtained from well-characterized cases of NIFID.
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