Thrombocytopenia is one of the most frequent causes for hematologic consultation in the practice of medicine and may be life threatening. Although the normal platelet count in humans (150–400 × 109/L) far exceeds the minimal level required to avoid pathologic hemorrhage (<50 × 109/L), a number of medical conditions either increasing the destruction of platelets or reducing their production enhance the risk of bleeding. This chapter discusses an approach to the diagnosis of thrombocytopenia, grouping various causes by mechanism of action and describing our current understanding of the pathogenesis, treatment, and prognosis. In the vast majority of patients, a cause of thrombocytopenia can be identified and effective therapy instituted.
Acronyms and Abbreviations
AFLP, acute fatty liver of pregnancy; AML, acute myelogenous leukemia; ACOG, American College of Obstetricians and Gynecologists ; ASH, American Society of Hematology; ADP, adenosine diphosphate; ATP, adenosine triphosphate; APLA, antiphospholipid antibody; ATRUS, amegakaryocytic thrombocytopenia with radioulnar synostosis; APS, antiphospholipid syndrome; ATG, antithymocyte globulin; ARC, Arthrogryposis-renal dysfunction-cholestasis; CAPTURE, Antiplatelet Therapy in Unstable Refractory Angina; CVID, common variable immunodeficiency; CAMT, congenital amegakaryocytic thrombocytopenia; CTP, cyclic thrombocytopenia; DIC, disseminated intravascular coagulation; EDTA, ethylenediaminetetraacetic acid; EPIC, Evaluation of 7E3 for the Prevention of Ischemic Complications; EPILOG, Evaluation of Percutaneous Transluminal Coronary Angioplasty to Improve Long-term Outcome of c7E3 GPIIb-IIIa Receptor Blockade; EPISTENT, Evaluation of Platelet IIb/IIIa Inhibitor for Stenting; FPD/AML, Familial platelet disorder with propensity to myeloid malignancy; Flt-1, fms-like tyrosine kinase-1; GP, glycoprotein; HELLP, hemolysis, elevated liver enzymes, low platelets; HUS, hemolytic uremic syndrome; HIT, heparin-induced thrombocytopenia; HCV, hepatitis C virus; HIV, human immunodeficiency virus; HPA, human platelet alloantigens; ITP, immune thrombocytopenia; IPD, inherited platelet disorders; IVIg, intravenous immunoglobulin; ICSH, International Council for Standardization in Hematology; IWG, International Working Group; IDA, iron deficiency anemia; LTA, light transmission aggregometry; MHC, major histocompatibility complex; MACE, modified antigen capture enzyme-linked ımmunosorbent assay; MAIPA, monoclonal antibody-specific immobilization of platelet antigens; MDS, myelodysplastic syndrome; NAIT, neonatal alloimmune thrombocytopenia; PAIgG, platelet-associated immunoglobulin G; sFlt1, soluble Flt1; SLA, systemic lupus erythematosus; Treg, T regulatory; TAR, thrombocytopenia with absent radii; TPO, thrombopoietin; TRA, thrombopoietin receptor agonist; TTP, thrombotic thrombocytopenic purpura; VEGF, vascular endothelial growth factor; VWD, von Willibrand Disease; VWF, von Willebrand factor.
Platelets are anucleate blood cells produced in the marrow by polyploid cells termed megakaryocytes and were described in the 19th century after the application of the improved compound microscope allowed these very small cells, 2 μM in diameter, to be identified. Many early investigators are associated with the discovery of blood platelets, including Alfred Donné, Georges Hayem, Guilio Bizzozero, and William Osler, but it was James Homer Wright who in 1906, using his special stain (later called Wright stain), described the morphology of platelets with their central granular area and marginal hyaline zone and established that they were the product of the fragmentation of marrow megakaryocytes. Clot retraction was discovered long before platelets, but Hayem, through a ...