THE renewed interest by physicians in detecting and treating muscle diseases and the increased awareness of them by the laiety has contributed, no doubt, to the more freqent diagnosis of muscular dystrophy in recent years. However, a large fraction of patients sent to our clinic with the diagnosis of muscular dystrophy were found to suffer from some other malady. The diseases most frequently mistaken for muscular dystrophy were polymyositis and the syndrome of "benign hypotonia." Polymyositis, with its protean manifestations and variable course, may mimic all of the forms of muscular dystrophy so closely that differentiation becomes especially difficult.
The diagnostic label of polymyositis is applied to a heterogeneous group of cases where muscle weakness is accompanied by one or more of the following clinical features: undoubted remission of weakness, muscular pain or tenderness, cutaneous eruptions accompanying the appearance or worsening of weakness, dysphagia, high levels of serum aldolase in