Prognosis and treatment of polymyositis with particular reference to steroid resistant patients.

Eight boys and six girls with polymyositis examined between 1967 and 1982 were studied. The mean age of disease onset was 5 years 5 months. The initial regimen was prednisolone, 1.2 to 2.3 mg/kg/day, and after four weeks this dose was decreased gradually to a maintenance level of 5 to 20 mg on alternate days. The total treatment period was 3 years 6 months on average. Eleven of the 14 children had a uniphasic course, and steroids were stopped without a resurgence of the disease: three were refractory to steroid treatment. One of these died of a cardiomyopathy seven years after the onset of the illness despite treatment with steroids and cyclophosphamide; the second was treated with adrenocorticotrophic hormone after prednisolone, but without benefit; and in the third a series of treatment with lympho-plasmapheresis and cyclophosphamide resulted in some improvement. As cardiac involvement in polymyositis may become overt if the disease persists for many years, patients refractory to steroids should be given alternative treatment.