Background Idiopathic inflammatory myopathies (IIM) comprise an heterogeneous group of systemic diseases, with an important morbidity and mortality, depending on different clinical subgroups.
Objectives To study clinical manifestations, survival, causes of death and prognostic factors in a cohort of patients with IIM, focusing on different clinical subgroups.
Methods All patients with diagnosis of IIM (criteria of Tanimoto) (1) and follow-up in outpatient clinic between January 1988 and December 2005 were included. Clinical data was retrieved from clinical history. Patients were classified into 3 clinical subgroups: mixed connective tissue disease (Alarcόn-Segovia criteria) and IIM (Tanimoto criteria) (MCTD); overlap syndrome (Rheumatoid Arthritis, Systemic Erythematosus Lupus, or Scleroderma, all according to ACR criteria, and IIM according to Tanimoto Criteria); and Primary Myositis (Tanimoto criteria, not fullfiling other connective tissue disease criteria). Anti-Jo-1-antibodies were examined by ELISA and Line Immuno Assay standard methods. Survival analysis was studied with Kaplan-Meier curves, Cox logistic regression and logrank statistics. P<0,05 value was considered as significant.
Results In the present study, 110 patients were included, with 7 cases (6,4%) lost to follow-up. The median age at diagnosis was 42±22 years, with a ratio men:women of 5:1 and a follow-up period of 12,8±8,5 years. Patients were classified as primary myositis (50%), overlap syndrome (28.2%), and MCTD (21.8%). 18.2% patients tested positive for anti-Jo-1 antibodies. Age and sex distribution were similar between clinical subgroups. Secondary myositis had higher frequency of serious infections (64.5% in overlap syndrome vs. 32.7% in primary IIM vs. 54.2% in MCTD; p=0.012), articular (93.5% vs. 61.8% vs. 95.8%; p<0.001), joint (87.1% vs. 67.3% vs. 100%; p=0.002), hematologic (77.4% vs. 47.3% vs. 79.2%; p=0.004), neurologic (45.2% vs. 7.3% vs. 50%; p=0.001), renal (29% vs. 5.5% vs. 29.2%; p=0.005) and pulmonary manifestations (54.8% vs. 32.7% vs. 66.7%; p=0.011). There was a higher frequency, although not significant, of antiboides anti-Jo-1 in overlap syndrome (29% in overlap syndrome vs. 18.2% primary IIM vs. 4.2% in MCTD; OR 2.5; IC 95%: 0.9-6.9; p=0.060). During follow-up, 31 patients died (30,1%). Main causes of death were infections in primary IIM and overlap syndrome, and cardiovascular disease in MCTD. Survival rates were lower in overlap syndrome compared to primary IIM and MCTD. In multivariate analysis, adjusting for age and sex, prognostic mortality factors were male sex (HR 4.7; IC 95%: 1.4-16.1; p=0.013) and pulmonar manifestations (HR 4.5; IC 95%: 1.2-16.7; p=0.026) in overlap syndrome, and serious infections (HR 9.9; IC 95%: 2.0-49; p=0.005) in primary IIM.
Conclusions In our cohort, patients with secondary IIM had a higher frequency of extramuscular manifestations. Overlap syndrome had the worst survival rates within clinical subgroups. Main causes of death were infections in primary IIM and overlap syndrome, and cardiovascular disease in MCTD. Mortality was associated with male sex and pulmonar manifestations in overlap syndrome, and with serious infections in primary IIM.
Tanimoto K et al. J Rheumatol 1995 Apr;22(4):668-74.
Disclosure of Interest None Declared