Characterization of relapses in adult idiopathic inflammatory myopathies

The objective of the current report was to determine the relapse rates and characterize the nature of relapses during the disease course of adult patients with idiopathic inflammatory myopathies (IIM). A retrospective cohort study of 53 medical records of patients with polymyositis (PM), dermatomyositis (DM), connective tissue disease (CTD)-associated myositis, and malignancy-associated myositis at an academic rheumatology center was performed. Medical records were reviewed to determine clinical presentation, initial treatment, and clinical follow-up, with an emphasis on relapses. Relapses were defined as a sustained elevation in serum creatine kinase (CK) levels in the absence of an alternative etiology. Patients were followed for an average of 65±43 months. All patients received corticosteroids, and 35 patients received additional immunosuppressive medications as part of their initial treatment. Serum CK levels normalized in 51 patients, and muscle strength normalized in 43 patients. Biochemical relapse was observed in 33 patients (65%). Patients with PM and CTD-associated myositis had a higher relapse rate compared to DM and malignancy-associated myositis patients. Multiple relapses were observed in 17 patients. Relapses tended to occur within the first 2 years after treatment initiation and during the tapering phase of treatment. No risk factors were unequivocally identified, although advanced age and increased duration of symptoms prior to treatment initiation had nonsignificant associations with increased risk of relapse. In conclusion, initial treatment of IIM results in a high rate of normalization of serum CK and muscle weakness. However, physicians should be aware of the high rate of relapse in patients with IIM.