alpha-chymotrypsin and Myositis

In 10 of 10 inclusion-body myositis (IBM) patients, including 1 hereditary case, vacuolated muscle fibers contained large or small cytoplasmic inclusions immunoreactive for alpha 1-antichymotrypsin (alpha 1-ACT). All IBM muscle biopsies had characteristic cytoplasmic tubulo-filaments by electron microscopy. None of 17 control muscle biopsies contained the alpha 1-ACT immunoreactive inclusions characteristic of IBM. In vacuolated muscle fibers, alpha 1-ACT immunoreactive inclusions colocalized with beta-amyloid protein and ubiquitin immunoreactivities. Our study provides the first demonstration of alpha 1-ACT accumulations in abnormal human muscle, and it suggest that, as in Alzheimer's disease and Down's syndrome, alpha 1-ACT may be involved in the pathogenesis of IBM.

Topics: Adolescent; Adult; Aged; Amyloid beta-Peptides; Brain; Child; Chymotrypsin; Cytoplasm; Humans; Immunohistochemistry; Inclusion Bodies; Microscopy, Electron; Middle Aged; Muscles; Myositis; Ubiquitins

Cases of proliferative myositis and fasciitis were studied immunohistochemically and ultrastructurally for further understanding of the nature of ganglion cell-like giant cells. Blood coagulation factor XIIIa, fibronectin, myoglobin, myosin, CPK MM, and alpha-1-antichymotrypsin were detected in three cases of proliferative myositis and two cases of proliferative fasciitis by the avidin-biotin-peroxidase complex method. Factor XIIIa (a fibrin-stabilizing factor) and fibronectin were strongly positive in the giant cells, but not in striated muscle fibers. A small quantity of myosin was demonstrated in the giant cells, but myoglobin and CPK MM were never demonstrated in these cells. No alpha-1-antichymotrypsin was demonstrated in the giant cells. One case of proliferative myositis showed ultrastructural features suggestive of fibroblast rather than muscle cell or histiocytic origin. Strongly positive factor XIIIa in the giant cells is suggestive of the fact that they are active fibroblasts.

Topics: Aged; alpha 1-Antichymotrypsin; Antigens, Surface; Chymotrypsin; Creatine Kinase; Factor XIII; Fasciitis; Female; Histocytochemistry; Humans; Immunoenzyme Techniques; Isoenzymes; Male; Microscopy, Electron; Middle Aged; Myoglobin; Myosins; Myositis; Transglutaminases