Background Clinical manifestations and prognosis of idiopathic inflammatory myopathies (IIM) are extremely heterogeneous which, combined with its low prevalence, makes difficult the study of the disease in the absence of multicenter studies.
Objectives To analyze the clinical characteristics and mortality in a cohort of patients diagnosed with IIM in rheumatology units from several hospitals in Madrid.
Methods A multicenter retrospective longitudinal descriptive study from REMICAM myositis study group was performed. All patients diagnosed with IIM according to Bohan and Peter1 criteria for myositis and in follow-up sometime between January 1980 and December 2014 in rheumatology units were included. Patients were classified into clinical subgroups: primary dermatomyositis (DM), primary polymyositis (PM), juvenile dermatomyositis (JDM), paraneoplasic myositis, overlap myositis (OM), inclusion body myositis (IBM) and necrotizing myositis (NM). Main causes of death and influence of age and sex were studied.
Results 485 cases were included in this study, with a medium age at diagnosis of 43,3±23,2 years and mean follow-up time of 11,3±19 years. Most cases were Caucasian (93%), and women (74,4%). The most frequent form of classification were primary myopathies (28,8% PM; 21% DM; 20,6% OM; 19,4% JDM; 8,3% paraneoplasic myositis; 1% IBM and 0.8% NM) and the most frequent myositis specific antibodies detected were anti-Jo-1 (16,3% anti-Jo-1; 4,1% anti-Mi-2; 2,7% anti-PM-Scl; 0,6% anti-SRP; 0,2% anti-Ku). 25,4% of patients died, with a higher mortality rate in men (32,5% vs. 22,9; p=0,04) and older age at onset (54,1±24,8 years vs. 37,2±26,4 years, p<0,001). The clinical subtypes with higher mortality were paraneoplasic myositis (70%) and OM (36%). Main causes of death were cancer (23,4%) and cardiovascular events (23,4%), followed by infections (22,4%), interstitial lung disease (7.5%) and other causes. In clinical subsets, main causes of death were infections in DM (37,5%), and cardiovascular disease in OM (32,3%) and PM (32,1%).
Conclusions In our cohort of IIM 25,4% of patients died, with a worse prognosis in men and older age at onset, mainly due to cancer and cardiovascular events. Cardiovascular events are the most important cause of death in PM and MCTD, and infections in DM.
Bohan A, Peter JB. N Engl J Med 1975 Feb 13;292(7):344-7.
Disclosure of Interest None declared