Thrombocytopenic conditions—autoimmunity and hypercoagulability: Commonalities and differences in ITP, TTP, HIT, and APS

Immune thrombocytopenia purpura (ITP), thrombotic thrombocytopenia purpura (TTP), heparin-induced thrombocytopenia (HIT), and antiphospholipid syndrome (APS) are clinical conditions associated with significant morbidity and mortality. These well-defined clinical syndromes have in common several properties: (1) their pathogenesis is immune mediated, specifically by autoantibodies; (2) thrombocytopenia is a hallmark in these four conditions; (3) except for the case of ITP, platelet and endothelial cell activation occurs in TTP, HIT, and APS, resulting in a prothrombotic state and an increased risk of thrombosis. Although these four immune-mediated syndromes are well-defined diseases, several case reports and studies have documented the association of two diseases in the same patient, illustrating the concept of the kaleidoscope of autoimmunity.