investigations
Last reviewed 10/2022
The diagnosis of dermatomyositis is made on the basis of the clinical picture and raised circulating muscle enzymes; most usefully, serum creatinine kinase, and serum aldolase; less characteristic are the changes in serum SGOT or serum LDH.
Muscle biopsy may be performed, which shows muscle necrosis, phagocytosis of muscle fibres, and an inflammatory infiltrate. A suitable area should be identified by electromyography.
Autoantibodies such as ANF and RF are often positive.
electromyography in polymyositis