Risk of Thromboembolism in ITP

ITP and Treatment Options

Immune thrombocytopenia (ITP) is a heterogeneous group of disorders characterized by autoimmune-mediated destruction of platelets as well as impaired production of platelets in the bone marrow. Various treatment approaches are used, ranging from high-dose immunoglobulins (IVIG) and corticosteroids to newer treatments like thrombopoietin receptor agonists (TPO-RA) or the anti-CD20 antibody rituximab and immunosuppressants, up to splenectomy.

Thromboembolic Events as a Complication of ITP

Several studies have also been published dealing with thromboembolism in the adult population with ITP. Thromboembolic events have been described in up to 8% of patients, including both venous and arterial events. Some studies even indicate an increased risk of thromboembolism in patients with ITP compared to the general population.

Risk Factors

Risk factors for thromboembolism can include ITP itself, due to pro-inflammatory manifestations – such as elevated pro-inflammatory cytokines. Another significant risk factor may be the treatment itself. Typical risk factors can include corticosteroids, especially in higher doses. IVIG can potentially contribute to thromboembolism through higher blood viscosity, platelet activation, or arterial vasospasm. Splenectomy has been described as a possible risk factor, especially for abdominal thrombotic events, but deep vein thrombosis or pulmonary embolism are also mentioned. Therefore, increased monitoring is recommended for patients post-splenectomy, particularly in the early period. The data available regarding TPO-RA administration are not entirely clear.

Other undeniable risk factors include present comorbidities: antiphospholipid antibodies, antiphospholipid syndrome, infections, malignancies, hyperlipidemia, and others. Factors such as age, potential obesity, pregnancy, or contraceptive use should also be considered.

Possible Preventive Measures

Patients undergoing splenectomy should be given postoperative thromboprophylaxis, typically with low-molecular-weight heparin (LMWH) at the usual dose if the platelet count is > 30,000/μl. The role of acetylsalicylic acid (ASA) in this indication is not entirely clarified.

Treatment of Thromboembolism in Patients with ITP

For the treatment of patients with ITP and thromboembolism, it is recommended to start treatment with unfractionated heparin (UFH) at half the therapeutic dose, with subsequent dose escalation if the initial dose was tolerated. UFH should later be replaced with LMWH. If the platelet count is > 30,000/μl, LMWH should be initiated at half the usual dose; if the platelet count is > 50,000/μl, a full dose of LMWH can be given. In cases of severe thrombocytopenia and the need for thromboembolism treatment, IVIG and corticosteroids can be administered to rapidly increase the platelet count above 30,000/μl.

Additionally, TPO-RA can be used to maintain a safe platelet count while reducing corticosteroid doses. Anticoagulation must not be administered to patients with life-threatening bleeding, regardless of platelet count. In patients with deep vein thrombosis, inserting a filter into the inferior vena cava can be considered.

For arterial thromboembolism, such as in coronary disease, the risk of myocardial infarction outweighs the risk of minor bleeding. In patients with a platelet count > 30,000/μl, ASA or other antiplatelet agents are recommended, just as in individuals without ITP. In patients with atrial fibrillation, anticoagulation with LMWH should be initiated, followed by a transition to warfarin with a lower target INR (e.g., 1.5–2.0), increasing only with good tolerance. In some patients, administration of TPO-RA has been found advantageous for maintaining platelet count.

Conclusion

Thromboembolic complications in patients with ITP pose a significant risk. Treatment and prevention must be personalized to minimize both bleeding and the risk of thromboembolism as much as possible.

(eza)

Source: Takagi S., Suzuki I., Watanabe S. Risk of thromboembolism in patients with immune thrombocytopenia. J Hematol Thrombo Dis 2015; 3: 1, doi: 10.4172/2329-8790.1000185.