Sporadic inclusion-body myositis: a proposed key pathogenetic role of the abnormalities of the ubiquitin-proteasome system, and protein misfolding and aggregation.

Sporadic inclusion-body myositis (s-IBM), the most common muscle disease of older persons, is of unknown cause and there is no successful treatment. We summarize our most recent findings in s-IBM muscle fibers, which demonstrate abnormalities of the ubiquitin-proteasome system, and abnormal accumulation, misfolding and aggregation of proteins. We propose that these changes, possibly provoked by the aging intra-muscle fiber cellular milieu, and aggravated by the oxidative stress, play a key pathogenic role in s-IBM. This evidence strongly suggests that mechanisms other than the immune/inflammatory response play the important role in s-IBM muscle fiber degeneration.