Heterogeneous inclusions in neurofilament inclusion disease.

Neurofilament inclusion disease (NFID) is a rare disease, whose pathogenesis remains to be elucidated. Immunoreactivity of ubiquitin-binding protein p62 has been reported in various neurodegenerative diseases, but it has not been studied in NFID. In this report we show p62 immunoreactivity in neuronal perikaryon of three cases of NFID. We found inclusions in NFID to be heterogenous based on immunoreactivity for alpha-internexin, phosphorylated neurofilament-H, p62 and ubiquitin. Moreover, we showed both p62- and alpha-internexin-immunoreactive inclusions within the perikarya of the same neuron. Electron microscopy findings support the notion that inclusions in NFID are heterogenous. The present study extends the list of proteins that have been identified as components of neuronal inclusions in NFID, and may help account for the pathogenesis of NFID.