Mortality in idiopathic inflammatory myopathy: results from a Swedish nationwide population-based cohort study.

Patients with idiopathic inflammatory myopathies (IIMs) suffer an increased burden of comorbidities, but data on mortality in recently diagnosed IIM are conflicting. Also, little is known when, if ever, in relation to IIM diagnosis, mortality is increased. METHODS: A population-based IIM cohort of patients diagnosed between 2002 and 2011 and general population comparators were identified using healthcare registers. They were linked to the cause of death register for follow-up. RESULTS: 224 (31%) of the 716 patients with IIM and 870 (12%) of the 7100 general population died during follow-up. This corresponded to a mortality rate of 60/1000 person-years in IIM and 20/1000 person-years in the general population. The cumulative mortality at 1 year after diagnosis was 9% in IIM and 1% in the general population, and increased in both IIM and the general population with time. The overall hazard ratio (HR) 95%CI of death comparing IIM with the general population was 3.7 (3.2 to 4.4). When we stratified on time since diagnosis, we noted an increase in mortality already within the first year of diagnosis compared with the general population, HR 9.6 (95% CI 6.9 to 13.5). This HR then plateaued around 2 after >10 years with the disease, although the estimates were not statistically significant. Malignancies, diseases of the circulatory and respiratory system were common causes of death. CONCLUSION: Mortality is increased in patients with contemporary IIM. The increased mortality was noted within a year of diagnosis, which calls for extra vigilance during the first year of IIM diagnosis.

Survival and cancer risk in an unselected and complete Norwegian idiopathic inflammatory myopathy cohort.

OBJECTIVE: To utilise an exposed/unexposed cohort strategy for mortality and cancer analyses across unselected and complete cohorts of patients with idiopathic inflammatory myopathy (IIM) resident in south-east Norway (denominator population 2.6 million), between 2003 and 2012. METHOD: IIM cases were identified by comprehensive searches through patient administrative databases followed by manual chart review. Polymyositis (PM) and dermatomyositis (DM) cases were classified by the Peter and Bohan and/or Targoff diagnostic criteria and sporadic inclusion body myositis (sIBM) by the European NeuroMuscular Centre (ENMC) criteria from 1997 and/or 2011. Every patient was matched for sex, age and residential area with 15 unexposed/non-IIM individuals drawn from the national population registry. RESULTS: Total mortality in the IIM cohort was 27% (87/326). Standardized mortality rate (SMR) was higher in DM (2.6) than PM (2.4) and sIBM (1.7). IIM-related causes of death were frequent (64%) and included cancer (all IIM subsets), aspiration (sIBM), pulmonary complications (PM/DM) and infections (PM/DM). Multivariate analyses identified age at diagnosis (PM and sIBM), positive anti-SSA (PM), cancer (DM), and DLCO < 60% (DM) as independent mortality risk factors. Cancer risk was increased in DM (standard incidence rate 2.0) and PM (SIR = 1.3), but not in sIBM (SIR = 0.9). Ovarian cancer was more prevalent in DM than in the general population (8.3% vs 1.1%). CONCLUSION: Our results suggest that mortality rates and cancer risk remain elevated in DM, and to a lesser degree also in PM. Mortality rate was also increased in sIBM, but some deaths appeared to be due to potentially preventable causes.

[Myositis-specific autoantibodies]. / Myosittspesifikke autoantistoffer.

BACKGROUND: Myositis-specific antibodies (MSA) are autoantibodies that are almost exclusively detected in idiopathic inflammatory myopathies (IIM). This article provides an overview of these autoantibodies and how they can be used clinically to identify subgroups of IIM. MATERIAL AND METHODS: The article is based on a non-systematic literature review and our own experience. RESULTS: MSA can be detected in up to 50 % of patients with IIM. Patients with anti-synthetase antibodies have a constellation of clinical findings termed "the anti-synthetase syndrome", in which interstitial lung disease dominates the clinical picture. Anti-Mi2 antibodies is another myositis-specific antibody. Patients with anti-Mi2 antibodies often have classical dermatomyositis, while the anti-SRP antibody identifies patients with severe myopathy, poor response to treatment with corticosteroids and histological findings of muscle cell necrosis - often lacking inflammatory infiltrates. The newly detected anti-CADMp140 appears to be associated with amyopathic or hypomyopathic dermatomyositis, previously called dermatomyositis sine myositis. Anti-p155 antibodies are most often found in patients who also have cancer. INTERPRETATION: Myositis-specific antibodies may be useful for identification of clinical subgroups of IIM and can thereby affect the choice of medical treatment.