Date: Sunday, October 21, 2018
Session Type: ACR Poster Session A
Session Time: 9:00AM-11:00AM
Background/Purpose: Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of autoimmune diseases with systemic involvement and excess mortality. We aim to describe the causes and evaluate predictors of mortality in patients at a tertiary-care academic medical institution in Singapore.
Medical records of patients newly diagnosed with IIM in the Department of Rheumatology and Immunology, Singapore General Hospital, between 2003-2017 were retrospectively reviewed. Patients recruited fulfilled the 2017 EULAR/ American College of Rheumatology (ACR) classification criteria for polymyositis (PM), dermatomyositis (DM), immune-mediated necrotizing myopathy (IMNM) and amyopathic dermatomyositis (ADM). Demographics, disease manifestations and treatment for cases were collected using a standardized protocol. In-hospital cause of death was determined by two independent reviewers according to categories set apriori. Person-years follow-up was calculated from date of cohort entry to either death or censor date. Univariate Cox proportional hazard (PH) regression was used to examine the association between each variable and mortality. We included both variables that were reported to be associated with mortality in the literature or variables with p<0.1 in the multivariate Cox regression model. We used the stepwise forward selection approach to select variables that were significant at p<0.05.
Of 100 patients (23% male, 76% Chinese), 58% and 40% fulfilled the definite and probable EULAR/ACR criteria for IIM respectively; 50% PM, 43% DM, 6% ADM and 1% juvenile myositis (Table 1). Mean age of diagnosis was 53.7 (SD 14.7) years, with 359.0 person-years follow-up from initial diagnosis. Of those who underwent a muscle biopsy (N=77), 99% had features consistent with that of an inflammatory myositis. 40% of all patients were positive for myositis-specific/associated antibodies. (Figure 1). Forty-one percent of all patients had interstitial lung disease (ILD). There were 26 deaths (26%), translating to mortality rate of 72.4 per 1000 patient years. 62% percent of deaths were due to infection (pneumonia [n=14], infective endocarditis [n=1], staphylococcus bacteraemia [n=1]), whilst 19% were due to ILD. In the multivariate analysis, Chinese ethnicity (HR 0.48 95% CI 0.24-0.96, p = 0.039) and male gender (HR 2.58 95% CI 1.22-5.50, p = 0.014) were independent predictors of mortality.
Conclusion: Pneumonia and ILD are the leading causes of death for IIM in this Asian cohort. Chinese and male gender were independent predictors of mortality.
- I.E. Lundberg, et al. 2017 EULAR/ACR classification criteria for adult and juvenile idiopathic inflammatory myopathies and their major subgroups. 2017. Ann Rheum Dis, 76 (12):1955-64.
Table 1: Baseline characteristics of patients recruited
|Male, n (%)||23 (23.0)|
|Chinese, n (%)||76 (76.0)|
|Non-Chinese, n (%)||24 (24.0)|
|Polymyositis, n (%)||50 (50.0)|
|Dermatomyositis, n (%)||43 (43.0)|
|Clinically Amyopathic Dermatomyositis, n (%)||6 (6.0)|
|Juvenile Dermatomyositis, n (%)||1 (1.0)|
|Clinical features and investigations:|
|Concomitant Autoimmune disease*, n (%)||21 (21.0)|
|Malignancy within 3 years of diagnosis, n (%)||16 (16.0)|
|Presence of ILD, n (%)||41 (41.0)|
|Asymptomatic, n (%)||12 (12.0)|
|Nonspecific interstitial pneumonia, n (%)||26 (26.0)|
|Usual interstitial pneumonia, n (%)||13 (13.0)|
|Organising Pneumonia, n (%)||4 (4.0)|
|Electromyogram, n (%)||88 (88.0)|
|Muscle biopsy done, n (%)||77 (77.0)|
|Patients with 1 MSA/MAA, n (%)||25 (25.0)|
|Patients with 2 MSAs/MAAs, n (%)||12 (12.0)|
|Anti-Jo-1, n (%)||14 (14.0)|
|Anti-Ro52, n (%)||14 (14.0)|
|Anti-MDA5, n (%)||5 (5.0)|
|Anti-SRP, n (%)||4 (4.0)|
|Anti-PM-Scl75, n (%)||4 (4.0)|
|Anti-TIF1g, n (%)||4 (4.0)|
|ESR, mm/Hr, mean (SD)||40 (30)|
|Creatine Kinase, U/L, mean (SD)||2889 (4388)|
|Aldolase, U/L, mean (SD)||40 (47)|
|Alanine aminotransferase, U/L, mean (SD)||107 (115)|
|Aspartate aminotransferase, U/L, mean (SD)||140 (142)|
|Lactose Dehydrogenase, U/L, mean (SD)||1290 (837)|
Abbreviations: ILD (Interstitial lung disease), HRCT (High-resolution computed tomography), ESR (Erythrocyte sedimentation rate)
*Autoimmune thyroiditis, Systemic sclerosis, Systemic lupus erythematosus, Rheumatoid arthritis, Sjögren syndrome, Microscopic polyangiitis
To cite this abstract in AMA style:Chuah TY, Kwan YH, Lui NL, Fong W. Risk Factors Associated with Mortality in Inflammatory Myositis: An Asian Perspective [abstract]. Arthritis Rheumatol. 2018; 70 (suppl 10). https://acrabstracts.org/abstract/risk-factors-associated-with-mortality-in-inflammatory-myositis-an-asian-perspective/. Accessed December 5, 2019.
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