Serum levels of interferon α do not correlate with disease activity in patients with dermatomyositis/polymyositis

Idiopathic inflammatory myopathies include three major diseases: dermatomyositis (DM), polymyositis (PM) and inclusion body myositis.1,–,3 The ethiopathogenesis of these entities is still not well understood. Recent studies show an important role of type I interferon (IFN) in the proinflammatory process leading to disease manifestations in muscle tissue.4,–,6 In order to investigate the relationship of soluble IFNα serum levels with clinical and laboratory characteristics we analysed serum samples of 43 patients with DM/PM (24/19 patients with DM and PM, respectively; 32 women/11 men). Patients were selected from a cohort of 81 PM/DM cases with the preference for those who were anti-Jo-1 positive, and had muscle MRI performed. In total, 44% of patients (n=19) were not treated prior to the collection of blood samples (group 1). Patients treated with ≤20 mg of prednisone per day at the time of blood draw were assigned to group 2 …