Apoptotic features accompany acute quadriplegic myopathy

Objective: To investigate the role of apoptosis in acute quadriplegic myopathy. Background: Acute quadriplegic myopathy is a muscular disease characterized by diffuse flaccid weakness occurring in patients with severe systemic illness and exposure to corticosteroids or neuroblocking agents. Myofiber atrophy and thick filament loss are the distinguishing pathologic features on muscle biopsy. Increased calpains expression and lysosomal and nonlysosomal proteolytic pathways have been claimed as possible pathogenic factors. Nevertheless, the mechanisms leading to myofiber atrophy and thick filament loss need further investigation. Patients and methods: The expression of ubiquitin and proapoptotic proteases as well as DNA fragmentation in muscle biopsies from three patients with acute quadriplegic myopathy were studied. Results: All patients exhibited an important overexpression of caspases, calpain, cathepsin B, and ubiquitin, and the presence of numerous apoptotic nuclei in over 70% of myofibers. Conclusions: These data suggest that apoptosis mediated by proteolytic proteases may play a role in the pathogenesis of acute quadriplegic myopathy.