Corticosteroid Induced Myopathy

Excerpt

Corticosteroid-induced myopathy is a highly prevalent toxic noninflammatory myopathy, which occurs as an adverse effect of prolonged oral or intravenous glucocorticoid use. It was first described in 1932 by Harvey Cushing, as part of a constellation of symptoms seen in Cushing syndrome. With the broader use of corticosteroids as therapeutic tools in the 1950s, corticosteroid-induced myopathy became a more well-known entity. This toxic noninflammatory myopathy typically has an indolent presentation and predominantly affects pelvic girdle muscles, and is associated with muscle weakness, atrophy, without associated pain. Acute steroid-induced myopathy in the critical care setting is another presentation. Workup typically reveals normal creatine kinase and no other signs of inflammatory disease, with EMG studies unremarkable and biopsy showing atrophy of type 2b fast-twitch muscle fibers. The diagnosis requires a high index of suspicion and is confirmed when muscle weakness improves after 3 to 4 weeks of tapering steroids, although improvement may take months to a year. Other than steroid withdrawal, other options include switching from fluorinated to nonfluorinated glucocorticoids, or alternate day dosing. Additionally, physical therapy in the form of resistance and aerobic exercise has shown in some studies to prevent and treat steroid-induced myopathy. As such, a program of screening for steroid-induced myopathy should be implemented in the appropriate patient population, and patients should be prescribed physical therapy as a preventive and treatment modality for this condition.