A platelet count that falls below the lower limit of normal, i.e., 150000/microliter (for adults) is defined as thrombocytopenia. Platelets are blood cells that help in blood clotting and wound healing — risks associated with thrombocytopenia range from no risk at all to bleeding risks and thrombosis. The correlation of severity of thrombocytopenia and bleeding risk is uncertain. Spontaneous bleeding can occur with a platelet count under 10000/microliter and surgical bleeding with counts below 50000/microL. Thrombocytopenia is associated with risk of thrombosis in conditions like heparin-induced thrombocytopenia (HIT), antiphospholipid antibody syndrome (APS), disseminated intravascular coagulation (DIC), thrombotic microangiopathy (TMA), paroxysmal nocturnal hemoglobinuria (PNH).
Normal platelet count range varies by different ages, sexes, and ethnicity. Women, young individuals, and non-Hispanic blacks have slightly higher platelet counts.
In normal conditions, platelets get removed by monocytes/macrophages of the reticuloendothelial system. The life span of platelets is 8 to 10 days.
In immune-mediated thrombocytopenia, anti-platelet autoantibodies bind to platelets and megakaryocytes, resulting in increased platelet destruction by the reticuloendothelial system and decreased platelet production.
Anti-platelets antibodies are present in primary ITP, drug-induced ITP, lymphoproliferative disorders, autoimmune conditions like SLE and in chronic infections like HEP C, HIV, and Helicobacter pylori.
Non-immune mediated increased platelet destruction occurs in mechanical valve replacement patients, preeclampsia/HELLP syndrome, DIC, and thrombotic microangiopathy. In conditions like DIC and thrombotic microangiopathy, increased platelet consumption within thrombi takes place.
Dilutional thrombocytopenia presents in massive fluid resuscitation and massive blood transfusion.
Redistribution of platelets:
In normal individuals, one-third of platelet mass is in the spleen. In conditions that cause splenomegaly and increases spleen congestion (cirrhosis) results in increased platelet mass in spleen and a decrease in circulating platelets.
Review of peripheral blood smear. Analysis of platelet size and morphology helps in identifying conditions that are associated with platelet destruction and increased platelet consumption.
Adhesion of platelets to polymorphonuclear cells is known as “platelet satellitism” can be identified by review of a peripheral blood smear.
A review of WBC and RBC morphology may suggest a specific condition.
History. Obtaining a thorough history helps to identify the etiology of thrombocytopenia. Patients with platelets greater than 50000/mL, rarely have symptoms. Patients with platelets under 20000/mL most likely have spontaneous bleeding.
Physical Examination includes examining the skin and other sites of bleeding and examination of liver, spleen, and lymph nodes. Bleeding caused by thrombocytopenia characteristically demonstrates petechiae, nonpalpable purpura, and ecchymosis. Dry purpura refers to purpura in the skin; wet purpura refers to purpura in the mucosa. Examine for hepatomegaly and splenomegaly which occur in lymphoma, chronic liver disease, and other hematologic conditions. Enlarged lymph nodes are present in infections, autoimmune disorders, lymphoma, and other malignancies.
Evaluation of patients with isolated thrombocytopenia includes obtaining a CBC, peripheral blood smear, HIV, and HCV tests.
In asymptomatic, mild thrombocytopenia patients, repeat CBC and routine monitoring is the recommended process.
Thrombocytopenic emergencies that require immediate action includes conditions of suspected HIT, TTP, HUS, drug-induced ITP, pregnancy with severe thrombocytopenia, bleeding with severe thrombocytopenia, urgently needed an invasive procedure in the presence of severe thrombocytopenia, leukopenia, and aplastic anemia.
In patients with bleeding and severe thrombocytopenia, treatment includes platelet transfusion.
Management includes identifying the underlying cause and treating it.
Primary immune thrombocytopenia:
This condition is a diagnosis of exclusion. First line treatment includes glucocorticoids and intravenous immune globulins; these agents inhibit autoantibody production and platelet degradation. Second line treatment includes rituximab, immunosuppressive drugs, and splenectomy. Third line agents are thrombopoietin receptor agonists, which stimulate platelet production.
TTP gets treated with plasma exchange.
In patients with secondary ITP managing the underlying condition is recommended, like, in SLE, SLE treatment is with immunosuppressive agents, and in patients with H. pylori-associated thrombocytopenia, eradication of H.pylori increases platelet count.
Psuedothrombocytopenia: Invitro platelet clumping results from ethylenediaminetetracetic acid (EDTA) dependent agglutinins, inadequately anticoagulated specimen, glycoprotein IIb/IIIa inhibitors. Giant platelets are counted as white blood cells rather than platelets by an automated counter.
A prospective study, it was found that patients with mild thrombocytopenia (100000 to 150000/microliter) have a 10-year probability of developing autoimmune disorders of 12 %.
Severe thrombocytopenia is associated with severe internal bleeding. Bleeding in the brain is fatal.
In heparin-induced thrombosis (HIT), arterial and venous thrombosis is seen leading to deep venous thrombosis, pulmonary embolism, cerebrovascular accident, and myocardial infarction.
In TTP microvascular thrombosis involving various organ systems predominantly central nervous system, whereas in HUS kidneys are affected.
Newly- diagnosed patients with thrombocytopenia are referred to a hematologist to confirm the diagnosis. In patients with unexplained thrombocytopenia, consulting hematologist is the recommendation. Immediate consultation is necessary for conditions like TTP, HUS, HIT, aplastic anemia, leukemia, and other bone marrow failure conditions.
Pregnant patients with HELLP/preeclampsia require an obstetrician consultation.
Educate patients about activity restrictions. Patients with a platelet count over 50000/mL should be cautious while participating in contact sports. Restriction from contact sports and other potentially traumatic activities is recommended in patients with platelets count under 10000/ mL.
Educate patients that certain over the counter medications like aspirin, Non-steroidal anti-inflammatory drugs, and ginkgo biloba interfere with platelet function. Educate patients about quinine-containing beverages and herbal teas, causing the low platelet count.
Due to the complexity of this condition, management of emergent thrombocytopenic conditions requires a multidisciplinary team of health care professionals, including specialty-trained nursing, pharmacists, physicians, and specialists working together collaboratively to achieve optimal patient outcomes.
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