Dermatomyositis

Abstract

Dermatomyositis (DM) is one of the idiopathic inflammatory myopathies. A set of criteria to aid in the diagnosis and classification of DM and polymyositis were first proposed in 1975 by Bohan and Peter. Four of the five criteria are related to the muscle disease: progressive proximal symmetrical weakness; elevated muscles enzymes; an abnormal electromyogram; and an abnormal muscle biopsy; while the fifth was the presence of compatible cutaneous disease. Subsequently it has been recognized that there are many patients with compatible cutaneous disease that do not have initial manifestations of their muscles as defined by clinical weakness and elevated enzymes. Some of these patients have subtle changes on biopsy, electromyogram or MRI at diagnosis, and some develop these changes and possibly clinical manifestations later, while a small group of patients never seem to develop clinical muscle disease. In the patient with amyopathic DM the prognosis is good in the absence of malignancy. For patients with muscle disease, the prognosis depends upon the severity of the muscle disease, the presence of lung disease, oesophageal dysfunction and/or malignancy. Children and adolescents with DM often develop calcinosis that can result in disability or discomfort. Classically, the diagnosis of DM is confirmed by the presence of typical muscle symptoms and findings along with elevated muscle enzymes, or an abnormal electromyogram and/or an abnormal muscle biopsy. Recently MRI became widely available and abnormalities of this test might be useful in diagnosis. Treatment provides control of the muscle inflammation and results in a return to normal function of the patient who might otherwise become disabled from the weakness. The skin disease is often symptomatic and is cosmetically displeasing, therefore the goal of therapy is to relieve the symptoms and improve the patient's self-image and ability to interact with other people. Some patients with DM have an associated malignancy, and treatment of the malignancy might in some patients result in a control of the disease process. In children with DM treatments are aimed also at the prevention of calcinosis, or when the calcinosis occurs, at its eradication. This presentation will focus on two issues: the relationship of DM to internal malignancy, including an approach to the search for cancer and the management of the patient with DM.