Rokkam Venkata R., Killeen Robert B., Kotagiri Rajesh
Banner University
University of Illinois
Once referred to ignobly as "blood dust," platelets are a component of blood produced in the bone marrow that have a vital role in the blood clotting process. The average platelet count in adults and children is usually between 150,000 and 450,000/μL (150 to 450 x 10/L), although the normal range may vary in different clinical laboratories. Thrombocytosis, or thrombocythemia, occurs when the platelet count exceeds 450,000/μL of blood. Thrombocytosis can be classified into primary and secondary (or reactive) thrombocytosis. This distinction is essential as it carries implications for evaluation, prognosis, and treatment. Primary thrombocytosis results from an unregulated abnormality in platelet production by bone marrow progenitor cells and is usually associated with myeloproliferative neoplasms. Primary thrombocytosis, especially in conditions such as essential thrombocythemia and polycythemia vera, carries an increased risk of thrombosis and bleeding compared to secondary thrombocytosis. Secondary thrombocytosis, also known as reactive thrombocytosis, is characterized by an abnormally high platelet count due to underlying events, infections or diseases, or certain medications. Secondary thrombocytosis, which is more common than primary thrombocytosis, is typically identified through routine laboratory studies. In most cases, secondary thrombocytosis symptoms are due to an underlying disorder rather than the thrombocytosis itself. Rarely, extreme thrombocytosis may lead to thrombotic events such as acute myocardial infarction, mesenteric vein thrombosis, and pulmonary embolism. Although secondary thrombocytosis is typically benign, the underlying causes—such as malignancy, connective tissue disorders, and chronic infections—can be associated with an increased risk of adverse outcomes. Approximately 80% to 90% of individuals with thrombocytosis are known to have secondary thrombocytosis. Causes of secondary thrombocytosis include transient conditions like acute blood loss or infection, as well as sustained factors such as iron deficiency, asplenia, cancer, chronic inflammation, or infectious diseases. Reactive thrombocytosis is a laboratory anomaly that generally resolves once the underlying causative condition is addressed.
血小板曾被不光彩地称为“血尘”，是骨髓产生的血液成分，在血液凝固过程中起着至关重要的作用。成人和儿童的平均血小板计数通常在150,000至450,000/μL（150至450×10⁹/L）之间，不过不同临床实验室的正常范围可能有所不同。当血小板计数超过450,000/μL血液时，就会发生血小板增多症，即血小板血症。血小板增多症可分为原发性和继发性（或反应性）血小板增多症。这种区分至关重要，因为它对评估、预后和治疗都有影响。原发性血小板增多症是由骨髓祖细胞血小板生成的无节制异常引起的，通常与骨髓增殖性肿瘤有关。与继发性血小板增多症相比，原发性血小板增多症，尤其是在原发性血小板增多症和真性红细胞增多症等情况下，血栓形成和出血的风险增加。继发性血小板增多症，也称为反应性血小板增多症，其特征是由于潜在事件、感染或疾病或某些药物导致血小板计数异常升高。继发性血小板增多症比原发性血小板增多症更常见，通常通过常规实验室检查来确定。在大多数情况下，继发性血小板增多症的症状是由潜在疾病引起的，而不是血小板增多症本身。极少数情况下，极端的血小板增多症可能导致血栓形成事件，如急性心肌梗死、肠系膜静脉血栓形成和肺栓塞。虽然继发性血小板增多症通常是良性的，但潜在病因，如恶性肿瘤、结缔组织疾病和慢性感染，可能与不良后果风险增加有关。已知约80%至90%的血小板增多症患者患有继发性血小板增多症。继发性血小板增多症的病因包括急性失血或感染等短暂情况，以及缺铁、无脾、癌症、慢性炎症或传染病等持续因素。反应性血小板增多症是一种实验室异常，通常在潜在病因得到解决后就会消退。
