ACUTE QUADRIPLEGIC MYOPATHY - ANALYSIS OF MYOSIN ISOFORMS AND EVIDENCE FOR CALPAIN-MEDIATED PROTEOLYSIS

Immunocytochemical analysis or muscle specimens from 5 patients with a cute quadriplegic myopathy indictes that depletion of either fast or s low myosin occurs in this disorder. The initial lesion consists of foc al myosin loss in nonatrophic fibers. Other structural proteins (actin , titin, nebulin) are spared or affected only at an advanced stage of the disease. Attempts at regeneration, evidenced by expression of feta l myosin and desmin, occur in some fibers. Calpain expression is marke dly enhanced in the affected fibers, implicating an altered calcium ho meostasis in the evolution of the pathologic process. By contrast, cat hepsin B and ubiquitin expressions are only minimally affected. The hi story of 1 of our patients indicates that severe systemic illness in a nd of itself can cause acute quadriplegic myopathy. (C) 1997 John Wile y & Sons, Inc.