Discussion on the Clinical and Electromyographic Aspects of Polymyositis

Among the very varied cases of flaccid paralysis it is necessary to recognize a group in which weakness and,muscular wasting are due to diffuse inflammatory changes in muscles. Though a syndrome of polymyositis has been known and described by many authors for nearly a hundred years, renewed interest in it is warranted for two reasons: (1) The frequent association of such muscular disease with skin changes-dermatomyositis being no longer a very uncommon diagnosis-and the recognition of the affinity of these cases with others of the so-called collagen-vascular or connective tissue diseases, especially scleroderma and lupus erythematosus. (2) The recognition that polymyositis may occur with no skin changes, or with minimal skin changes, and that the clinical picture then closely resembles that of primary muscular dystrophy. Though such cases are uncommon, they are not so rare as to be unimportant, for the very practical reasons that the prognosis and treatment may be quite different from those of true muscular dystrophy. They present a fairly well-defined clinical picture and a histological picture in a muscle biopsy which is usually distinctive. They have a varied course, sometimes rapid in onset and progress, sometimes insidious and chronic; and they may occur either in childhood or in adult life. They can be separated clearly from septic or parasitic infections of muscles, e.g. trichiniasis, but their etiology is as obscure as that of collagen-vascular diseases generally. In trying to define the clinical pictures I shall deal first with a group of cases in childhood which are probably of this nature. With the co-operation of Dr. John N. Walton I have recently studied, and published an account of, 8 children who recovered from an illness diagnosed in each case as muscular dystrophy (Nattrass, 1954). I shall mention some details of one or two only and summarize the others.