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

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. 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. 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),