Relationships between clinical features and distribution of mononuclear cells in muscle of patients with polymyositis.

We examined the relationships between the clinical features and outcome of 43 patients with polymyositis-dermatomyositis (PM-DM) and muscle biopsy findings, with specific reference to the pattern of distribution of inflammatory cells. Perifascicular inflammation was associated with the presence of the rash of DM. No relationships were found between the other patterns of distribution of inflammatory cells in muscle and various clinical findings in patients with PM-DM, or the clinical course of the disease. Vasculitis of large vessels (greater than or equal to 20 micron) was seen in only 5 cases (11%) and was not present in childhood PM-DM.