Background Idiopathic Inflammatory Myopathies (IIM) comprise an heterogeneous group of systemic diseases, with an important morbidity and mortality, depending on different age of onset.
Objectives To study clinical manifestations, survival and causes of death in a cohort of patients with IIM, focusing on different age at onset.
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 5 serological subgroups examined by ELISA and Line Immuno Assay standard methods (anti-Jo-1 antibodies, anti-U1-RNP, anti-PM-Scl, anti-Mi-2 and anti-Ku) and 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). Patients were classified into adult-onset IIM (A-IIM) and childhood-onset IIM (PED-IIM). 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. 92 patients (83.6%) were classified as A-IIM, and 18 patients (16.4%) as PED-IIM. Mean age at diagnosis was 48±19 years for A-MII and 12±4 years for PED-IIM, with a higher frequency of women among PED-IIM (80.4% for A-IIM vs. 100% for PED-IIM; p=0.04). Distribution into serological and clinical subgroups was similar between both groups, with a higher frequency, although not significant, of MCTD in PED-IIM (19.6% in A-IIM vs. 33.3% in PED-IIM; p>0.05) and anti-U1-RNP antibodies (33.7% vs. 55.6%; p=0.08).There were no differences in the distribution of other clinical and serological subgroups. Regarding clinical manifestations, PED-IIM had a higher frequency of arthritis (52.2% vs. 83.3%; p=0.015), and classical cutaneous dermatomyositis lesions, such as Gottron papules (12% vs. 33.3%; p=0.033) and heliotrope rash (16.3% vs. 38.9%; p=0.04). There were no significant differences between both groups regarding frequency of interstitial lung disease (70.5% in A-IIM vs. 66.7% PED-IIM) or other organ involvement. During follow-up, 31 patients died, 29.3% in A-IIM and 22.2% in PED-IIM, with a mean survival of 23.7±1.8 years for A-IIM and 27.3% ± 2.8 years for PED-IIM, without statistical differences. Main causes of death were infections and cardiovascular disease in both groups.
Conclusions In our cohort, patients with childhood-onset IIM had a higher frequency of female distribution, arthritis and classical cutaneous dermatomyositis lesions compared to adult-onset IIM. Frequency of interstitial lung disease and anti-Jo-1 antibodies were similar between both groups. Survival rates and main causes of death were similar between adult-onset and childhood-onset IIM.
Tanimoto K et al. J Rheumatol 1995 Apr;22(4):668-74.
Disclosure of Interest None Declared
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