Clinical Characteristics and Associated Factors for Infection and in-Hospital Mortality in Inpatients with Polymyositis/Dermatomyositis in China: A Retrospective Study.

Purpose: To investigate the clinical features of infection, and associated factor for in-hospital mortality in a southern Chinese cohort with polymyositis/dermatomyositis (PM/DM). Patients and Methods: Clinical data were retrospectively reviewed from 2015 to 2022 from a tertiary hospital in southern China. Associated factors for infection and in-hospital mortality were analyzed by multivariate logistic regression analysis. Results: A total of 554 patients with PM/DM were included, and 35.6% (197/554) of them developed 404 episodes of infection. Half of the patients developed infection within 4 months after disease onset. Bacterial infection was predominant (249/404, 61.6%). Lung was the most involved (242/404, 59.9%). Gram-negative bacteria the leading pathogens (64/84, 76.2%). Patients with anti-MDA5 positive were prone to develop severe infections (35.1% vs 16.4%, P<0.001) and had higher mortality (11.7% vs 3.4%, P=0.01). The in-hospital mortality was 6.5% (36/554). Infection was the leading cause of death (20/36, 55.6%). Older age (adjusted odds ratio (OR): 1.05, 95% confidential interval (CI): 1.02-1.09, P=0.004), ILD (adjusted OR: 2.76, 95% CI: 1.11-6.84, P=0.03), number of episodes of infection (adjusted OR: 1.91, 95% CI: 1.53-2.38, P<0.001), and elevated serum creatinine (Scr) (adjusted OR: 6.83, 95% CI: 1.77-26.40, P=0.01) were associated with in-hospital mortality. Conclusion: Infection is an early complication in PM/DM with a high proportion of lung involvement and predominance of gram-negative bacteria. It is a major contributor to in-hospital mortality. Older age, ILD, and number of episodes of infection are associated with poor prognosis.