Venous thromboembolism in patients with dermatomyositis and polymyositis

Objective. To assess the incidence of venous thromboembolic events in dermatomyositis and polymyositis patients, and associated factors. Methods. We retrospectively studied a cohort of 123 myositis patients (87 dermatomyositis, 36 polymyositis) from a single centre and identified cases with deep vein thrombosis and/or pulmonary embolism. Type of myositis, association with cancer, presence of thrombophilia, disease activity, and intravenous immunoglobulin therapy were analysed. Incidence rates were calculated on the basis of time to first venous thrombotic event. Patients with less than 12 months' follow-up were excluded. Results. Six new first thromboembolic events occurred in 6 of 96 patients studied (6.3%), all with dermatomyositis. Median time to development of venous thromboembolism was 4.3 months (IQR, 0.8-8.8) after the dermatomyositis diagnosis. Venous thromboembolism was significantly associated with intravenous immunoglobulin therapy (p < 0.05) and older age (p < 0.05), but not with cancer. All events (100%) occurred during active myositis. The incidence density of venous thromboembolism among patients with dermatomyositis according to the first year of follow-up was 9.3 per 1000 person-years (95% CI, 3.4 to 20.3). Conclusion. A trend toward venous thromboembolism was detected in patients with dermatomyositis.