Polymyositis and Dermatomyositis

Laboratory FeaturesElevation of sarcoplasmic enzymes in serum (creatine phosphokinase, aldolase, transaminases and lactic dehydrogenase) is valuable both for diagnosis and for following the clinical activity and response to treatment. Although some state that the transaminases are the most reliable,31,33,35 most authorities favor the creatine phosphokinase.2These serum enzymes are not infallible guidelines, for occasionally they remain entirely within the normal range despite active myositis1,51; likewise, when muscle atrophy is extensive in long standing disease, the enzymes may be normal despite active myositis. Motor-neuron diseases, Duchenne muscular dystrophy and other dystrophies, metabolic disorders, endocrinopathies, toxins . . .