Background Mortality of idiopathic inflammatory myositis (IIM) is high, and some studies explored the outcome in IIM patients with different clinical and serologic phenotypes[1]. However, few studies focused on the prognosis of the entire IIM patients, and compared their prognostic factors.

Objectives To clarify the mortality and independent risk factors related to death of IIM patients in a large multi-center prospective registry cohort in China.

Methods Patients registered before 31^st, December 2021 were included in our analysis. The baseline information at enrollment including demographics, comorbidities, clinical manifestations, immune indices, laboratory data was summarized. Death information was retrieved from our database and supplemented by National death surveillance system in China. Kaplan-Meier Curves as well as cumulative survival at 1, 3, 5 and 10 years was depicted, and Log-rank test was used to compare the mortality between different subgroups. Univariable Cox hazards regression analysis was used to identify potential risk factors for death, and factors with P value <0.05 were further analyzed using multivariable Cox regression model.

Results 4695 IIM cases were finally enrolled in our analysis, including 3012 dermatomyositis (DM; 64.2%), 616 polymyositis (PM; 13.1%), 951 antisynthetase syndrome (ASS; 20.2%), and 116 immune-mediated necrotising myopathy (IMNM; 2.5%). 72.8% were female. The median (interquartile range) follow-up time since disease onset was 33 (15-48) months, and the median interval in months between disease onset and diagnosis.279 cases were complicated with malignancy (6.3%). 550 deaths in total were recorded. The cumulative survival for the entire IIM patients at 1, 3, 5 and 10 years were 92.3%, 88.2%, 85.6%, and 79.7% (Figure 1a). A significant difference (P<0.05) in survival between different subgroups confirmed by log-rank test was observed (Figure 1b). Malignancy (126 cases, 22.9%) was the most frequent cause of deaths (Figure 1c), followed by cardiovascular diseases (98 cases, 17.8%), respiratory failure due to ILD (98 cases, 17.8%) and infections (98 cases, 17.8%). 51 myocardial infarctions/ischemic heart diseases caused the most death cases in the cardiovascular diseases group. Notably, most of infective cases were lung infections (82 cases). 5 (0.9%) suicides were also worth the whistle. Multivariable Cox hazard ratio proportional hazards model confirmed malignancy (HR=4.95, 95%CI 4.05-6.07), male (HR=1.58, 95%CI 1.33-1.88), ILD (HR=1.38, 95%CI 1.12-1.71), skin ulceration (HR=1.60, 95%CI 1.22-2.10), anti-Jo-1 antibody (HR=0.54, 95%CI 0.39-0.75), anti-MDA-5 antibody (HR=1.93, 95%CI 1.46-2.56), and anti-Ro 52 antibody (HR=1.29, 95%CI 1.05-1.58) as independent risk factors for mortality after adjusting for age (Figure 1d).

Conclusion The high mortality rates of IIM patients in China gave us an alert about their situation. As expected, malignancy was the biggest causes of death, again reminding us of importance for screening malignancy in IIM patients. The management of coronary artery diseases was also crucial considering nearly 1/10 deaths were caused by myocardial infarctions/ischemic heart diseases. High suicide rates revealed bad psychological states of IIM. Male patients had a significantly higher risk compared to female patients. ILD was a strong independent risk factor and also a major cause of death in IIM, emphasizing the center place of ILD in IIM management. Intensive immunosuppressive treatment and monitoring might be applicated in these patients. Anti-MDA-5 antibody and anti-Ro52 antibody predicted worse prognosis, while anti-Jo-1 antibody indicated a better one.

Reference [1]Li S, Sun Y, Shao C, et al. Prognosis of adult idiopathic inflammatory myopathy-associated interstitial lung disease: a retrospective study of 679 adult cases. Rheumatol Oxf Engl 2021;60:1195–204.

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Figure 1.

Acknowledgements: NIL.

Disclosure of Interests None Declared.