P148 Long-term survival of patients with idiopathic inflammatory myopathies: Anatomy of a single-center cohort
Authors: Guimarães Francisca , Yildirim Resit , Isenberg David A 
Published: April 2023

Abstract

Background/Aims
Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of immune-mediated systemic diseases, characterized by muscle inflammation and multiple systemic manifestations. We aimed to characterize clinical manifestations, course, treatment, and mortality of IIM patients. We have also attempted to assess predictors of mortality in IIM.

Methods
Retrospective single center study IIM patients followed between 1980 and June 2022, including IIM patients fulfilling three or four of the Bohan and Peter criteria. Patients were divided in 6 groups: adult-onset polymyositis (APM), adult-onset dermatomyositis (ADM), juvenile-onset dermatomyositis (JDM), ‘overlap’ myositis (OM), cancer-associated myositis (CAM), and antisynthetase syndrome (ASyS). Sociodemographic, clinical and immunological features and treatment were collected. Additionally, disease complications and causes of death were recorded. The log rank test was used to compare survival curves between subgroups. The Cox proportional hazards regression was used to assess predictors of mortality.

Results
A total of 158 patients were included with a mean age at diagnosis of 40.81±15.63 years. Most patients were female (77.2%) and Caucasian (63.9%). The most frequent diagnoses were ADM (35.4%), OM (20.9%) and APM (24.7%), respectively. The majority of patients presented with both upper and lower limb involvement (89.2%), with a mean creatinine kinase level of 4423 ± 7633 U/L. Electromyography, muscle biopsy and magnetic resonance were positive for active myositis in 81.3% (104/128), 77.7% (101/130) and 40.9% (54/132), respectively. Antinuclear antibodies were positive in 62.4% of the patients. Remitting and relapsing (RR) was the most common disease course (35.4%). Most patients were treated with a combination of steroids and one-to-three immunosuppressive drugs (74.1%). Interstitial lung disease, gastrointestinal and cardiac involvement were frequent, affecting 38.5%, 36.5% and 23.4% of the patients, respectively. The survival rates at 5, 10, 15, 20 and 25 years of follow-up were 89%, 74%, 67%, 62% and 43%, respectively. During a median follow up of 13.61 ± 10.24 years, 46 (29.1%) have died, mainly due to infection (28.3%), followed by malignancy (19.6%) and cardiovascular events (10.9%). Positive biopsy (p = 0.044), Jo-1 (p = 0.039), malignancy (p = 0.026), cardiac involvement (p = 0.011) and infections (p = 0.016) were associated with mortality. Older age at diagnosis (HR:1.058, 95CI 1.031-1.085), cardiac involvement (HR: 3.23, 95CI 1.60-6.53), and malignancy (HR 2.20, 95CI 1.09-4.44) were independent predictors of mortality.

Conclusion
IIM is a rare disease with important systemic complications. Older age at diagnosis, cardiac involvement, and malignancy are independent predictors on mortality. Early diagnosis and aggressive treatment of cardiac involvement could improve survival of these patients.
Disclosure
F. Guimarães: None. R. Yildirim: None. D.A. Isenberg: None.