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Causes and pathogenesis of thrombotic thrombocytopenic purpura
Last reviewed: 06.07.2025
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The causes of thrombocytopenic purpura are not precisely established; among the factors preceding the development of idiopathic thrombocytopenic purpura, viral and bacterial infections (40% of cases), vaccinations and gamma globulin administration (5.5%), surgical operations and injuries (6%) are noted; in 45% of cases, the disease occurs spontaneously without previous causes. In most patients with idiopathic thrombocytopenic purpura, the premorbid background, physical and psychomotor development do not differ from healthy children.
The term "idiopathic" indicates a spontaneous onset of the disease and an etiology that has not yet been identified.
Pathogenesis of thrombocytopenic purpura. Thrombocytopenia leads to a disorder in the platelet link of hemostasis and contributes to the development of hemorrhagic syndrome of the petechial-spotted (microcirculatory) type. Thrombocytopenia is accompanied by angiotrophic insufficiency, which causes dystrophic changes in the endothelium of small vessels and capillaries and leads to a decrease in the resistance of the vascular wall and an increase in its porosity for erythrocytes. This is manifested by small-point hemorrhages (petechiae) in places with higher hydrostatic pressure (lower limbs); the number of petechiae can be easily increased by using compression of the limbs with a tourniquet.
Hemorrhagic syndrome in idiopathic thrombocytopenic purpura is characterized by prolonged bleeding from small vessels due to the inability of platelets to form a platelet plug at the sites of endothelial damage. Significant changes occur in the vascular wall and under the influence of the pathoimmune process. Due to the commonality of the antigenic structures of platelets and endothelial cells, endothelial cells are destroyed by antiplatelet antibodies, which increases the clinical manifestations of hemorrhagic syndrome.
In the pathogenesis of idiopathic thrombocytopenic purpura, the immunopathological synthesis of antiplatelet autoantibodies (IgG) by splenic lymphocytes is of key importance. They are fixed on various receptors of platelet and megakaryocyte membranes, which confirms the pathoimmune nature of the disease and the hypothesis of primary dysfunction of the lymphoid system in idiopathic thrombocytopenic purpura. Due to the autoimmune process, platelets lose their adhesive-aggregation properties and quickly die, being absorbed by mononuclear cells in the spleen, and in more severe cases - in the liver and other organs of the reticuloendothelial system ("diffuse" type of sequestration). With the "diffuse" type of platelet sequestration, splenectomy is not effective enough. The half-life of their disappearance is half an hour or less.
In idiopathic thrombocytopenic purpura, the number of megakaryocytes in the bone marrow, although significantly increased, is characterized by functional immaturity (the number of immature forms increases, while the number of functionally active ones decreases).