Ultrastructural observations in myopathy complicating Cushing's disease.

The ultrastructural findings in a muscle biopsy of a patient with Cushing's disease associated with severe myopathy are described. They included pronounced mitochondrial damage, thickening and deep invaginations of the sarcolemmal basement membrane, and thickening of the basement membrane of the capillaries. In addition, the muscle fibers showed a marked degree of disarray and wide interfibrillar spaces, containing large numbers of vacuoles, which presented degenerated mitochondria. The similarity between these findings and the ultrastructural features of corticosteroid-induced myopathy is discussed.