Risk Factors for Thrombosis in Immune Thrombocytopenia

Immune thrombocytopenia (ITP) is a rare autoimmune disease (annual incidence: 3-4/105 inhabitants) leading to an increased risk of spontaneous bleeding. ITP is said "primary" when not associated to other systemic disease (lymphoma, systemic autoimmune disease, chronic infectious disease…). First-line treatment is based on corticosteroids. Intravenous immunoglobulin (IVIg) is added in case of serious bleeding. In about 70% of adult cases, ITP becomes persistent or chronic (lasting \>3 months and \>12 months, respectively). Second-line treatments are then indicated. Among them, thrombopoietin-receptor agonists (TPO-RAs), romiplostim and eltrombopag are increasingly used. Splenectomy is used as ultimate treatment. Paradoxically, the risk of thrombosis is higher in ITP patients in comparison with the general population, due to the release of young hyperactive platelets from bone marrow. The incidence of thrombosis in ITP patients has been estimated between 0.5 and 3/100 patients-years. However, risk factors for thrombosis in ITP are not known, except splenectomy that is used in very few patients now. The role of other ITP treatments in thrombosis occurrence has been evoked, particularly for corticosteroids and IVIg. TPO-RAs have been associated with a risk of thrombosis in clinical trials and pharmacovigilance studies, even in case of low or normal platelet count. However, this risk has not been measured in the real-life practice, adjusted for other risk factors for thrombosis.