Hereditary platelet function disorders are rare and result in a lifelong bleeding tendency. The diagnosis is made by platelet aggregation tests. In order to control heavy bleeding, platelet transfusions are usually required.
A normal hemostasis requires the platelet adhesion and activation.
Hereditary platelet function disorders are rare and result in a lifelong bleeding tendency. The diagnosis is made by platelet aggregation tests. In order to control heavy bleeding, platelet transfusions are usually required. A normal hemostasis requires the platelet adhesion and activation. For adhesion (.. D h of platelets with contact to the vascular subendothelium), both the Von Willebrand Factor (vWF) and the glycoprotein Ib – / – IX complex needed. The activation requires the glycoprotein IIb – / – IIIa complex, by which the platelet aggregation and the binding of fibrinogen to be promoted. When activation is adenosine diphosphate (ADP) released from platelet storage granules, and arachidonic acid converted by the enzyme cyclooxygenase into thromboxane A2. The released ADP acts on the P2Y12 receptors on other blood platelets, which they are activated and recruited to the site of injury. In addition ADP causes (and thromboxane A2) then changes in glycoprotein IIb – / – IIIa complex; by the subsequent increased fibrinogen it comes to the clumping of platelets. In congenital platelet dysfunction can occur at each of these steps to malfunction. Patients with pre-existing lifelong bleeding disorders in which the platelet and coagulation tests are normal, a disease must be accepted in this form circle. The diagnosis is usually made based on platelet aggregation tests; However deliver platelet aggregation tests no quantitative results, and often the interpretation is ambiguous (see Table: Results of aggregation tests in hereditary platelet function disorders). Results of aggregation assay in hereditary platelet disorders disease collagen, epinephrine, and ADP (low doses) ADP (high dose) ristocetin disorders of the amplification of platelet activation Decreases Normal Normal thrombasthenia (z. B. loss of the glycoprotein IIb / IIIa receptor) missing missing normal or reduced Disorders of platelet adhesion (eg. B. Bernard-Soulier syndrome, = von Willebrand’s disease) Normal Normal Decreases ADP adenosine diphosphate. Adhäsionsstörungen A rare autosomal recessive disease is the Bernard-Soulier syndrome. Here, the platelet adhesion is due to a defect of the glycoprotein Ib – / – IX complex which VWF binds the endothelium, disturbed. It can cause severe bleeding. The platelets are unusually large (giant platelets). There is no aggregation rather than by the addition of ristocetin aggregation with ADP, collagen and epinephrine, however, is normal. Giant platelets in combination with functional disorders also occur during May-Hegglin syndrome, a disease with disturbed thrombocytopenic leukocytes, and the Chediak-Higashi syndrome (Chediak-Higashi syndrome). In order to control heavy bleeding, platelet transfusions are necessary. A deficiency or defect in the charge of the platelet von Willebrand factor (VWF) results in von Willebrand’s disease (von Willebrand’s disease). It is usually treated with desmopressin or VWF replacement with pasteurized intermediate purity factor VIII concentrates, which contain VWF. Disorders of the release reaction diseases that affect the release reaction in platelet activation, are the most common hereditary platelet dysfunction and cause minor bleeding. They may be caused by a reduced ADP content in the platelet granules (storage pool deficiency), by disturbances in the conversion of arachidonic acid to thromboxane A2 or by disorders of platelet aggregation in response to thromboxane A2. Platelet aggregation tests show reduced aggregation after the addition of collagen, epinephrine, and low-dose ADP. A normal aggregation occurs after addition of high-dose ADP. The same pattern occurs after taking NSAIDs or aspirin and may last for several days. Therefore, platelet aggregation tests should not be performed in patients who have taken these drugs recently. The thrombasthenia (Glanzmann’s syndrome) is a rare autosomal recessive disease in which a defect of platelet glycoprotein complex IIb / IIIa is present that prevents the aggregation of the platelets. In patients severe mucosal bleeding may occur, for example. B. nosebleeds, which is controlled only by the application of a tamponade, and transfusion of platelets. confirms the diagnosis if not form platelet aggregates with the addition of epinephrine, collagen or high-dose ADP, however, a temporary aggregation is observed with ristocetin. In order to control heavy bleeding, platelet transfusions are necessary.