Abstract
Steroid myopathy is caused by excessive amount of glucocorticoids (GC) of endogenous or, more frequently, exogenous origin. Its underlying condition is atrophy of muscle fibres.
Type-II muscle fibres are involved preferentially and the atrophy is dominantly based on induction of proteolysis and concomitantly decreased proteosynthesis and due to dysregulation of muscle growth factors insulin-like growth factor-I (IGF-I) and myostatin. It develops after long-term use of high-dose of GC, the fluorinated forms are of higher risk.
The main manifestation is progressive painless skeletal muscle weakness affecting predominantly proximal and limb-girdle muscles, normal or slightly elevated serum levels of muscle enzymes are often seen. The treatment is based on reduction or cessation of GC use; in case of endogenous origin of GC the underlying disease needs to be treated.