Objectives: In patients with ANCA-associated vasculitis (AAV), an increased incidence of venous thromboembolism (VTE), mainly during active disease, has been described. In a large cohort of AAV patients, we assessed the incidence of VTE and its relation with disease activity and classic risk factors for VTE.
Methods: Patients newly diagnosed with AAV between 1990 and 2005 and treated with cyclophosphamide and corticosteroids were included. Data were retrospectively retrieved from charts and by questionnaire. The incidence of VTE associated with and following a diagnosis of AAV was calculated (VTE/100 person-years) and related to periods with active disease.
Results: One hundred and ninety-eight patients with AAV were followed for 6.1 (0.2-17.6) yrs. In 23 patients (12%), 25 VTEs (17 deep venous thromboses, 3 pulmonary emboli, 5 both) occurred in association with AAV, of which 52% occurred during active disease, defined as 3 months before and after diagnosis or relapse of AAV. Overall, VTE incidence was 1.8/100 person-years, increasing to 6.7/100 during active disease. VTEs occurred significantly less frequently in patients with WG than in patients with microscopic polyangiitis and renal limited vasculitis. Classic risk factors were present in most patients at some moment during follow-up. There were no significant differences in classic risk factors between patients with and without AAV-associated VTE.
Conclusions: Patients with AAV have an increased risk of developing VTEs, especially when AAV is active. This finding could not be explained by classic risk factors, but is probably related to endothelial changes and hypercoagulability induced by AAV and its therapy.