Platelet reduction may be due to immunological causes (viral infection, drugs, connective tissue or lymphoproliferative diseases, blood transfusions) or non-immunological diseases (sepsis, ARDS). It show up petechiae, purpura and mucosal bleeding. The laboratory findings depend on the cause. Sometimes only the history may lead to the diagnosis. Therapy means treatment of the underlying disorder.
Platelet reduction may be due to immunological causes (viral infection, drugs, connective tissue or lymphoproliferative diseases, blood transfusions) or non-immunological diseases (sepsis, ARDS). It show up petechiae, purpura and mucosal bleeding. The laboratory findings depend on the cause. Sometimes only the history may lead to the diagnosis. Therapy means treatment of the underlying disorder. Acute respiratory distress syndrome (ARDS) patients with ARDS (Acute hypoxic respiratory failure (AHRF ARDS)) can develop a non-immunological thrombocytopenia, possibly secondary to remaining of platelets in the pulmonary capillary bed. Blood transfusions In the Post-transfusion purpura there is an immunologically mediated degradation of platelets. This is not of the immune thrombocytopenia (ITP Immune Thrombocytopenia ITP) () to define, except for the fact that within the previous 7-10 days a blood transfusion has taken place. The patients, mostly women, a platelet antigen (PLA-1), which is present in most people lack. The transfusion of PLA-1 positive platelets stimulates the production of anti-PLA-1 antibodies that can react by an undefined mechanism with the PLA-1-negative platelets of the patient. The consequences are severe thrombocytopenia, which subside within 2-6 weeks. A treatment by i.v. Immunoglobulin usually takes place successfully. Connective tissue and lymphoproliferative diseases connective tissue diseases (e.g., B. SLE) or lymphoproliferative disorders (z. B. lymphoma) may lead to an immunologically mediated thrombocytopenia. Corticosteroids and the usual for immune thrombocytopenia measures are effective; the treatment of the underlying condition is not always prolongs remission. Drug-associated immune thrombocytopenia medicines frequently used, occasionally induce thrombocytopenia, are heparin quinine trimethoprim / sulfamethoxazole glycoprotein IIb – / – IIIa inhibitors (e.g., abciximab, eptifibatide, tirofiban.) Hydrochlorothiazide carbamazepine acetaminophen chlorpropamide ranitidine rifampicin vancomycin occurs drug-induced thrombocytopenia in on the rule when a binding to platelets drug and a new “foreign” antigen forms, whereby an immune response is triggered. This disease is, apart from taking drugs in medical history, indistinguishable from the immune thrombocytopenia. After discontinuation of the drug platelet value rises again within 1-2 days and returned to normal within 7 days. (A table of thrombocytopenia inducing drugs with references of the causal relationship between drug and thrombocytopenia is available at Platelets on the Web.) Occurs at up to 1% of patients A heparin-induced thrombocytopenia (HIT) obtained unfractionated heparin. Even if heparin is taken in very low doses (eg. Heparin solution to hold open vascular access), it may come to heparin-induced thrombocytopenia. The usually is based on an immunological mechanism. Bleeding occur rarely, but it happens more often to the formation of thrombi that can cause vascular occlusion and life-threatening paradoxical arterial and venous thrombosis (z. B. thromboembolic occlusion of limb arteries, stroke, acute myocardial infarction). Heparin should be discontinued in all patients who develop thrombocytopenia and a new thrombosis or their platelet counts drop by more than 50%. Any heparin should be discontinued immediately and alleged; Tests for the detection of antibodies against platelet factor 4 bound to the heparin to be performed. The anticoagulation with anticoagulants of the non-heparin group (z. B. argatroban, bivalirudin, fondaparinux) is at least as long as required until the platelet counts have recovered. Low molecular weight heparin (LMWH) is less immunogenic than unfractionated heparin, but can not be given to patients with heparin-induced thrombocytopenia, as most antibodies against heparin-induced thrombocytopenia cross-react with LMWH. Lepirudin is no longer available. Warfarin should be replaced in patients with heparin-induced thrombocytopenia not by heparin and, if a long-term anticoagulation is required only begin after recovery of platelet count. Clinical calculator: pretest probability heparin-induced thrombocytopenia (4-T-Score) infections HIV infection can cause an immunologically induced thrombocytopenia that is clinically indistinguishable from the immune thrombocytopenia. If glucocorticoids are given, the platelet count may increase. However, since these drugs lead to a further suppression of the immune system, corticosteroids are often administered only at values ??<20,000 / ul. Platelet counts often are rising as a result of the initiation of antiviral treatment. Hepatitis C infection is often associated with thrombocytopenia. An active infection can cause thrombocytopenia that is indistinguishable from an immune thrombocytopenia with platelet counts <10,000 / ul. Easier thrombocytopenia (platelet count 40,000 to 70,000 / ul) may develop due to liver damage. The formation of the hematopoietic growth factor, thrombopoietin which regulates the megakaryocyte and platelet production is thereby reduced. The hepatitis induced thrombocytopenia as the immune thrombocytopenia (immune thrombocytopenic purpura (ITP): treatment) treated. Other infections, such as systemic viral infections (eg. As Epstein-Barr virus, cytomegalovirus), Rickettsia infections (eg. As Rocky Mountain Spotted Fever) and bacterial sepsis are often associated with thrombocytopenia. Pregnancy About 5% of women occurs in late pregnancy in usually asymptomatic thrombocytopenia (Gestationsthrombozytopenie). They usually runs in a mild form (platelets <70,000 / ul are rare), does not require treatment and disappear after delivery. However, severe thrombocytopenia in pregnant women with preeclampsia can and HELLP syndrome (hemolysis, elevated liver enzymes and low platelet counts, pre-eclampsia and eclampsia) develop. For women, it is the birth must be initiated immediately in the rule; is the platelet count <20,000 / ul (or <50,000 / ul, if a Caesarean section is scheduled), a platelet transfusion should be considered. Sepsis Sepsis often leads to a non-immunological thrombocytopenia, the extent of which is parallel to the severity of the infection. This thrombocytopenia various reasons for disseminated intravascular coagulation; Formation of immune complexes, which bind to platelets; Complement activation, attachment of platelets to damaged endothelial surfaces; Damage to the glycoprotein on the platelet surface and apoptosis of platelets.