Ultrasound in the inflammatory myopathies.

Dermato- or polymyositis must be diagnosed or ruled out early because early immunosuppressive therapy prevents irreversible muscle degeneration. Acute poly- and dermatomyositis are accompanied by normal or increased size, low echogenicity, and elevated perfusion of affected muscles, whereas in chronic poly- and dermatomyositis, the size and perfusion of affected muscles are reduced and echogenicity is increased. Although magnetic resonance imaging is more sensitive in detecting edema-like muscular changes and thereby acute myositis, contrast-enhanced ultrasound with its capability of measuring perfusion has become a useful diagnostic tool in diagnosing acute inflammation in poly- and dermatomyositis.