IDIOPATHIC INFLAMMATORY MYOPATHIES - INCLUSION-BODY MYOSITIS, POLYMYOSITIS, AND DERMATOMYOSITIS

In this review, the main emphasis is on new advances concerning sporad ic inclusion-body myositis and hereditary inclusion-body myopathy. Pol ymyositis and dermatomyositis are reviewed briefly. Hypotheses are pre sented regarding the possible cause and significance of abnormally acc umulated beta-amyloid protein, two other epitopes of beta-amyloid prec ursor protein, hyperphosphorylated tau, alpha1-antichymotrypsin, ubiqu itin, and prion protein in sporadic inclusion-body myositis and heredi tary inclusion-body myopathy. Because most of those proteins are also accumulated at the neuromuscular junction, ''junctionalization'' of ot her muscle fiber nuclei is a possibility. Attention is given to the fa ct that vacuolated muscle fibers in hereditary inclusion-body myopathy may represent early changes because they are virtually free of congop hilic amyloid deposit but, like sporadic inclusion-body myositis, cont ain large accumulations of beta-amyloid protein and prion.