Dermatomyositis is frequently unrecognized because of lack of familiarity with its variable clinical manifestations. In the advanced stage of the illness the diagnosis is seldom difficult. This report concerns the clinical and laboratory findings and biopsy observations on muscle in the cases of 9 patients with dermatomyositis who were observed in Vanderbilt Hospital during one year. A certain number of the cases in this series were atypical, yet there were sufficient significant features to justify this diagnosis.
The cause of dermatomyositis is unknown. Frequently the earliest symptom is preceded by an acute infection. Although this disease may occur at any age, it usually occurs between the ages of 10 and 50 years. There is no significant sex predominance. Pathologically the salient lesions are present in the striated muscles; however, many other structures may be implicated. The onset of the disease may be abrupt or insidious; remissions and exacerbations are frequent.