Thrombosis in inflammatory bowel disease: clinical setting, procoagulant profile and factor V Leiden

Patients with inflammatory bowel disease have an increased frequency ofthromboembolism, and microvascular thrombosis has been proposed as acontributory pathogenic factor. The mechanism of enhanced procoagulantactivity is not understood. We examined the clinical setting ofthromboembolic events in 52 patients with Crohn's disease or ulcerativecolitis, and assessed the procoagulant laboratory profile, including FactorV Leiden, in a subset of 20 patients to identify procoagulant risk factors.Patients who developed thrombosis tended to be young; 60% of thromboticevents occurred in patients under 50 years. Multiple thromboembolicepisodes occurred in 13% and unusual sites of thrombosis (e.g.intracardiac, cerebral, inominate veins) in 11%. No risk factor wasidentifiable in 52% of cases and two-thirds of thromboses occurred in anout-patient setting. The mortality rate was 8%. Evidence for inflammatorydisease activity was found in only 45% of patients with ulcerative colitisat the time of the thromboembolic event, in contrast to 89% of those withCrohn's disease. Assays for specific coagulation defects were negative inall cases tested (protein S, C were normal in 17/17; anti-thrombin III,anti-phospholipid antibodies and activated protein C resistance werenegative in 20/20, and only 1/20 patients was found to be heterozygous forFactor V leiden. Thrombosis in inflammatory bowel disease is importantbecause it occurs in a young population, often in unusual sites, and has ahigh mortality. The development of thrombosis is related to activeinflammatory disease in most patients with Crohn's disease but apparentlynot in those with ulcerative colitis. Since approximately half of thepatients had no other identifiable risk factor, there remains a substantialgroup of patients with IBD who develop thrombosis for unknown reasons.