Comparison between idiopathic deep vein thrombosis of the upper and lower extremity regarding risk factors and recurrence

Summary.  Background:  The pathogenesis and natural course of idiopathic upper extremity deep vein thrombosis (UEDVT) are unclear. Objective:  To compare patients with UEDVT and with idiopathic lower extremity deep vein thrombosis (LEDVT) regarding risk factors and recurrence. Methods:  We followed 50 patients with first idiopathic UEDVT and 841 patients with first idiopathic LEDVT for an average of 59 and 46 months, respectively. We excluded patients with natural inhibitor deficiency, lupus anticoagulant, cancer, pregnancy, isolated pulmonary embolism (PE), or long‐term antithrombotic treatment. The endpoint was recurrent venous thromboembolism (VTE). Results:  In comparison to LEDVT patients, UEDVT patients were younger (38 ± 13 years vs. 49 ± 16 years, P  < 0.001), slimmer (body mass index: 24 ± 4 vs. 27 ± 5, P  < 0.001), less frequently had a family history of VTE (18% vs. 31%, P  = 0.06) or concomitant PE (8% vs. 31%, P  =0.001), were less frequently carriers of factor V Leiden (12% vs. 30%, P  = 0.009), and had lower thrombin generation marker levels (D‐dimer, 283 ± 361 ng mL −1 vs. 456 ± 446 ng mL −1 , P  < 0.001; peak thrombin, 298 ± 101 n m vs. 363 ± 111 n m , P  = 0.001). Recurrence occurred in two of 50 patients with UEDVT (4%) and in 129 of 841 patients with LEDVT (15%). After 5 years, the likelihood of recurrence was 2% [95% confidence interval (CI) 0–6] among UEDVT patients and 19% (95% CI  16–22; P  = 0.02) among LEDVT patients. As compared to LEDVT patients, the adjusted risk of recurrence was 0.26 (95% CI  0.06–1.05; P  = 0.059) in UEDVT patients. Conclusion:  The pathogenesis and natural course of the disease differ between patients with idiopathic UEDVT and LEDVT.