Diagnostic Role of Antiphospholipid Antibodies and Microparticles in Immune Thrombocytopenic Patients With Thrombosis

Immune thrombocytopenia (ITP) is an acquired autoimmune disorder characterized by isolated thrombocytopenia and an increased risk of bleeding. Paradoxically, ITP is also associated with an increased risk of thrombosis (1).

Recent studies showed that the occurrence of thrombosis in patients with ITP is not purely accidental and can be considered a clinical reality with an important impact on the management of the disease (2).

The pathophysiological mechanism for thrombosis in ITP remains unclear. Sever bleeding episodes are relatively rare in some patients with ITP although having low platelet count, suggests that these patients may have a protective factor against bleeding (3).

Antiphospholipid (aPL) antibodies are a heterogeneous group of autoantibodies with high affinity for phospholipids such lupus anticoagulant (LA), β2glycoprotien І (β2GPІ), and anticardiolipin (anti-CL). They interfere with physiological mechanisms of coagulation and fibrinolysis, leading the haemostatic balance towards coagulation. Moreover, it seems to affect the physiological function of various cells such as platelets and endothelial cells (4).

Microparticles (MPs) are a diverse group of bioactive small-sized vesicles (100-1000nm) that can be found in body fluids and blood after activation, necrosis, or apoptosis of almost all cells. Although most MPs in human blood originate from platelets, MPs are also released from leukocytes, erythrocytes, endothelial cells, smooth muscle cells and cancer cells (5). They participate in intercellular communication and play a major role in homeostasis under physiological conditions and also in diseases (6). The most prominent property of MPs is their procoagulant potential, mainly based on phosphatidylserine exposure and tissue factor expression (7).