Acute myopathy with selective degeneration of myosin filaments following status asthmaticus treated with methylprednisolone and vecuronium

We report two cases of severe, acute myopathy with selective degeneration of myosin filaments in asthmatics who developed respiratory failure with hypercapnia and acidosis requiring endotracheal intubation, administration of vecuronium and prolonged ventilatory support. Hypoxia was documented in one case and probably present in the other. Both patients received prolonged treatment with high doses of intravenous methylprednisolone. Flaccid quadriparesis was noted after discontinuation of vecuronium. Muscle biopsy showed nonspecific myopathic changes on light microscopy. Electron microscopy revealed selective loss of myosin filaments in many fibers. Recovery occurred within 2 months with supportive treatment. This entity is probably related to a combination of high doses of corticosteroids, vecuronium administration and metabolic abnormalities associated with respiratory failure.