Pattern of adult onset of polymyositis and dermatomyositis and association with malignancy.

A retrospective study of 22 adult patients with dermatomyositis (DM) or polymyositis (PM) was performed. Male to female ratio was 1:2.7. Mean age of onset was 37.3 +/- (16.3) and symptoms were present for a mean of 11.2 +/- 14.6 months before diagnosis. Primary polymyositis was diagnosed in 11 (50%), primary dermatomyositis in three (13.6%). PM/DM was associated with connective tissue disease in three (13.6%) and malignancy in five patients (22.7%). Muscle disease followed the diagnosis of malignancy by a mean of 12.2 months (one to 36 months). All were female. Diffuse erythema was observed in all three patients with DM and malignancy. Arthritis was seen more frequency in our patients (55%). Sixty-eight percent of patients showed substantial improvement of muscle disease with steroids alone or in combination with other immunosuppressive agents, 18% did not improve or their disease progressed in spite of the treatment. Three patients died (14%), two from respiratory failure and one from underlying malignancy.