Retrospective cohort study of coincident autoimmunity in dermatomyositis.

Patients with one autoimmune disease are at an increased risk for developing more, but no studies have evaluated coincident autoimmune disease in dermatomyositis (DM). This retrospective study seeks to determine the most common coincident autoimmune diseases in patients with DM. The most common coincident autoimmune diseases in the DM cohort included ulcerative colitis (11.11%), Sjogren's syndrome (10.56%) and systemic lupus erythematosus (10.56%). Patients with DM had 15 times the odds of developing one of the coincident autoimmune diseases compared with the control group (95% confidence interval 11.71-21.35, P < 0.0001). Clinicians caring for patients with DM should carefully surveil their patients for development of coincident autoimmune disease.