[A multi-center retrospective study of organ involvement in adult patients with polymyositis or dermatomyositis].

Objective: To explore the prevalence and characteristics of main organ involvement in adult patients with polymyositis (PM) or dermatomyositis (DM) and determine their specific relative factors.
Methods: Using unified questionnaire, we retrospectively collected the medical records of 1 387 confirmed adult PM/DM patients from 2007 to 2012 at 22 rheumatology centers in China. Statistical analyses were performed with chi-square or Fisher exact test and multivariate analyses with logistic regression.
Results: A total of 1 387 patients were collected with 460 (33.2%) PM and 927 (66.8%) DM. The female:male ratio was 2.4: 1. Their onset age was ( 47 ± 14) years. A total of 1 031 (74.3%) patients had organ involvement. The prevalence of pulmonary involvement, arthritis, gastrointestinal and cardiac involvement were 44.6%, 32.3%, 21.9% and 20.3% respectively. The multivariate analysis indicated that older onset age (P < 0.01) was positively associated with pulmonary involvement while myalgia (P < 0.05) was negatively associated. Fever (P < 0.05), weight loss (P < 0.05) and Raynaud's phenomenon (P < 0.01) were positively associated with arthritis while muscle weakness (P < 0.05) negatively associated. Weight loss (P < 0.05), Raynaud's phenomenon (P < 0.01) and muscle weakness (P < 0.05) were positively associated with gastrointestinal involvement. Weight loss (P < 0.05) and swollen limbs (P < 0.05) were positively associated with cardiac involvement.
Conclusion: The prevalence of organ involvement is high in adult PM/DM patients. Our study may aid the diagnosis of organ damage in PM/DM patients.