What provokes thrombocytopathy?

Acquired thrombocytopathy. Violation of the functional properties of platelets is noted in many cases of severe infection and somatic diseases, but this is rarely accompanied by the development of hemorrhagic syndrome. The development of hemorrhagic syndrome in these diseases is often provoked by the appointment of physiotherapeutic procedures (UHF, UFO) or drugs that have side effects in the form of inhibition of the functional activity of platelets (medicinal, iatrogenic thrombocytopathies).

With acquired medicinal thrombocytopathies, hemorrhagic syndrome is often provoked by the simultaneous administration of several platelet-forming drugs. Among the thrombocytopoies, acetylsalicylic acid takes a special place, which in small doses (2.0-3.5 mg / kg) inhibits platelet aggregation, provoking the development of hemorrhagic syndrome, but in large doses (10 mg / kg) inhibits the synthesis of prostacyclin - an adhesion inhibitor and platelet aggregation to the damaged vascular wall, thereby promoting thrombogenesis.

Acquired thrombocytopathy is also found in hemoblastoses, B12-deficiency anemia, renal and hepatic insufficiency, DIC syndrome, scurvy and endocrinopathies.

With acquired thrombocytopathy, it is necessary to analyze the patient's pedigree, conduct a functional evaluation of platelets in parents and close relatives to exclude unrecognized hereditary forms of thrombocytopathy. Some hereditary diseases of the exchange of amino acids, carbohydrates, lipids and connective tissue are also accompanied by secondary thrombocytopathy (Marfan, Ehlers-Danlos syndromes, glycogenoses).

Hereditary thrombocytopathy is a group of genetically determined biochemical or structural abnormalities of platelets, which are accompanied by a violation of their haemostatic functions. Hereditary thrombocytopathies are the most common genetically determined hemostatic defect, detected in 60-80% of patients with recurrent bleeding of the vascular-platelet type and, presumably, in 5-10% of the population.

Depending on the type of molecular and functional disorders, the following types of hereditary thrombocytopathy are distinguished:

1. pathology of membrane proteins - receptors (glycoproteins) to endothelial collagen, von Willebrand factor, thrombin or fibrinogen - is manifested by a violation of adhesion and / or platelet aggregation
2. defects of platelet activation ("gray" platelet syndrome), due to the inadequacy of alpha and beta granules with substances involved in platelet activation, coagulation, and the formation of platelet thrombus. The defect is manifested by a violation of platelet activation and aggregation, delayed coagulation, retraction and platelet thrombus formation
3. a violation of the metabolism of arachidonic acid - is manifested by a violation of the synthesis of thromboxane A ₂ and platelet aggregation
4. violation of mobilization of Ca ^{2+ ions} - is accompanied by a violation of all types of platelet aggregation
5. deficiency of the third platelet factor - is manifested by a violation of the interaction between platelets and blood coagulation factors by retraction of the blood clot.

The absence of a complex of glycoproteins (GP) IIb / IIIa on their membrane, and hence the inability to bind fibrinogen, aggregate with each other, cause a retraction of the blood clot, is the basis of the defect in the functional activity of thrombocytes in thrombastenia (described in 1918 by the Swiss pediatrician Glanzmann). The combination IIb / IIIa is a receptor specific for platelets and megakaryocytes by an integrin complex mediating extracellular signals to the cytoskeleton of platelets, which initiates their activation by isolating mediators of vascular platelet hemostasis.

Hereditary membrane defects are the cause of the inability of platelets in atrombia to aggregate, with the Bernard-Soulier anomaly-to the binding of von Willebrand factor and adhesion to collagen. With different variants of hereditary thrombocytopathy with a defect in the release reaction, deficiencies of cyclooxygenase, thromboxane synthetase, etc., which lead to disruption of the mediator release of hemostasis, are revealed. With some hereditary thrombocytopathies, there is a deficit of dense granules (Khurdzhmansky-Pudlak disease, Landolt syndrome), a deficiency of protein granules (a syndrome of "gray" platelets) or their components, lysosomes. In the genesis of increased bleeding in all cases of thrombocytopathy, the most important is the violation of platelet interaction with each other, with the plasma link of hemostasis, the formation of the primary hemostatic plug.

Functional properties of platelets in the most common hereditary thrombocytopathies

Thrombocytopathy	The nature of the functional defect (diagnostic criteria)
Primary
Thrombosis	Absence or reduction of platelet aggregation induced by ADF, collagen and adrenaline, absence or sharp decrease in retraction of the blood clot
Atrombium	Reduction of platelet aggregation induced by ADP, collagen and adrenaline with normal retraction of the blood clot
Thrombocytopathy with impaired release response	A sharp decrease in platelet aggregation: normal primary aggregation, but no or sharp decrease in the 2nd wave of aggregation
Bernard-Soulier disease	Reduced platelet aggregation, induced by ristocetin, bovine fibrinogen in normal aggregation with ADP, collagen, adrenaline
Secondary
Von Willebrand's Disease	Normal aggregation of platelets with ADP, collagen, adrenaline, reduced with ristomycin (defect is corrected by donor plasma). The level VIII has been lowered. Decreased adhesive ability of platelets
Afibrinogenemia	The level of fibrinogen in the blood is sharply reduced in combination with reduced platelet aggregation