Prospective evidence of increased venous thromboembolism in hereditary hemorrhagic telangiectasia.

Hereditary Hemorrhagic Telangiectasia (HHT) is a rare vascular disease (1/5,000 prevalence) characterized by mucocutaneous telangiectasias and visceral arteriovenous malformations. Although hemorrhagic manifestations predominate, patients may also be at increased risk of thrombotic events. Previous studies on this topic have been mostly retrospective, and prospective data are lacking. We conducted a prospective registry-based study using a validated adjudication system to assess the incidence of venous thromboembolism (VTE) in subjects with a definite diagnosis of HHT. A total of 315 patients were included (mean age 54.3 ± 17.8 years; median 57, IQR 18-93; 42.2% > 65 years; 172 men, 143 women). Median follow-up was 14 months (IQR 6-99). Fifteen VTE events occurred, yielding an overall incidence of 23.1/1,000 patient-years. Incidence was 45.1/1,000 patient-years in subjects > 65 years-old and 11.6/1,000 patient-years in those ≤ 65 years-old. Four events were unprovoked, and eleven had identifiable provoking factors. In 4 cases, the provoking factor was hospitalization for an acute disease or the exacerbation of a chronic condition; none of these patients received in-hospital thromboprophylaxis. The observed VTE incidence in HHT appears higher than in the general population, particularly among older individuals. Underuse of prophylaxis may contribute to this excess risk. These findings underscore the need for individualized strategies that balance hemorrhagic and thrombotic complications in HHT.