Idiopathic myositis: a rheumatological view

Twenty five patients with idiopathic myositis attended this department for long term follow up from 1980 to 1989. Twelve patients had primary polymyositis (four men, eight women) and six had primary dermatomyositis (three men, three women); five women had an overlap syndrome. Two patients had a malignant condition associated with the myositis. The mean age at diagnosis was 40 years. All of the patients had proximal muscle weakness, 18/25 had a raised creatine kinase value (mean 2325 IU/l), 19/20 had an abnormal electromyogram, and 19/24 had positive muscle biopsy samples. Of the disease specific antibodies, anti-Jo-1 was detected in only 1/21 patients tested (three patients with fibrosing alveolitis were negative for this antibody), but the 56 kDa antibody was detected in 12/17 patients. The HLA data analysed in the white patients (17/25) showed that 6/8 of those tested were HLA-DR3 positive. All patients were treated with prednisolone and azathioprine was used for 14/25 patients. Only three deaths occurred during the eight year follow up, but there was a substantial morbidity, which may reflect the referral pattern. Muscle strength tests and creatine kinase levels were useful in recording the response to treatment in some patients. These data emphasise that careful long term follow up of patients with myositis is mandatory and that although the present treatment strategy has substantially reduced the death rate, morbidity associated with the disease remains a major problem.