Chapter 38 - Thrombocytopenia and Thrombocytosis

Chemotherapy results in which condition? a. Acquired thrombocytopenia b. Inherited thrombocytopenia c. Acquired splenic sequestration d. Inherited thrombocythemia

*a. Acquired thrombocytopenia Wide arrays of chemotherapeutic agents used for the treatment of hematologic and nonhematologic malignancies suppress bone marrow megakaryocyte production and the production of other hematopoietic cells. Drug-induced thrombocytopenia is often the dose-limiting factor for many chemotherapeutic agents.

A 28-year-old woman sees her family physician complaining of easy bruising and menorrhagia. She has a platelet count of 60 × 10^9/L. All other hematology and routine coagulation tests are normal. She has a platelet-associated immunoglobulin G (IgG) autoantibody in her serum. Which is most likely? a. Chronic immune thrombocytopenic purpura b. Thrombotic thrombocytopenic purpura c. Acute immune thrombocytopenic purpura d. Hemolytic uremic syndrome

*a. Chronic immune thrombocytopenic purpura Chronic immune thrombocytopenic purpura is most often seen in women between the ages of 20 and 50 years of age. Patients most often complain of easy bruising, recurrent epistaxis, and menorrhagia. Platelet destruction in chronic immune thrombocytopenic purpura is the result of an IgG autoantibody, with various membrane glycoproteins being the most frequent targets.

A patient in the intensive care unit has anemia, schistocytes, and thrombocytopenia. The PT and PTT are elevated, and the fibrinogen is low. What diagnostic test should be used? a. D dimer to confirm acute DIC b. Bone marrow to confirm immune thrombocytopenic purpura c. Platelet antibody against P1A1 to confirm heparin-induced thrombocytopenia d. Platelet aggregometry to confirm posttransfusion purpura

*a. D dimer to confirm acute DIC In acute DIC, the D dimer is elevated, along with the other laboratory findings listed. None of the other conditions listed have the prolonged PT and PTT, low fibrinogen, and elevated D dimers.

What is the probable cause for thrombotic thrombocytopenic purpura? a. Deficiency of a metalloprotease needed to enzymatically degrade unusually large von Willebrand factor (VWF) multimers b. Abnormal synthesis of unusually large VWF multimers by endothelial cells c. Abnormal synthesis of unusually large VWF multimers by megakaryocytes d. Abnormal complexing of normal VWF multimers to create unusually large VWF multimers

*a. Deficiency of a metalloprotease needed to enzymatically degrade unusually large von Willebrand factor (VWF) multimers Patients with the more common form of thrombotic thrombocytopenic purpura are deficient in a metalloprotease (ADAMTS 13) needed to cleave unusually large VWF into the smaller VWF multimers normally found in plasma. Both endothelial cells and megakaryocytes normally make these unusually large VWF multimers.

What kind of antibody causes neonatal alloimmune thrombocytopenia? a. Maternal antibody against a fetal platelet antigen inherited from the father b. Fetal antibody directed against maternal platelet antigen c. Fetal antibody against a fetal platelet antigen inherited from the father d. Maternal autoantibody against a mother's platelet antigen

*a. Maternal antibody against a fetal platelet antigen inherited from the father Neonatal alloimmune thrombocytopenia develops when a mother develops an alloantibody against a platelet antigen inherited by the fetus from the father. These antibodies cross the placenta, bind to the antigen-bearing fetal platelets, and cause their premature destruction.

A patient has a platelet count of 650 × 10^9/L. The other hematology tests are normal. No evidence of hemostasis failure exists. Which is most likely? a. Reactive thrombocytosis b. Essential thrombocythemia c. DIC d. Polycythemia vera

*a. Reactive thrombocytosis The term reactive thrombocytosis refers to an abnormally high platelet count, typically more than 450 × 10^9/L, secondary to inflammation, trauma, or some other underlying and seemingly unrelated conditions. The platelet count does not usually exceed 800 × 10^9/L, and the elevation is transient.

Binding of therapeutic heparin to platelet factor 4 is used in testing to confirm: a. heparin-induced thrombocytopenia. b. acute immune thrombocytopenic purpura. c. chronic immune thrombocytopenic purpura. d. aspirin resistance.

*a. heparin-induced thrombocytopenia. Heparin-induced thrombocytopenia (HIT) is a good example of immune complex-induced thrombocytopenia, the fourth mechanism of drug induced thrombocytopenia. Binding of therapeutic heparin to platelet factor 4 (PF4), a protein released by activated platelets, or binding of PF4 to the platelet membrane causes a conformational change in PF4, resulting in the exposure of neoepitopes.

What is the correct term to describe a platelet count of 550 × 10^9/L when all other complete blood count (CBC) results are basically normal? a. Normal b. Thrombocytosis c. Thrombocytopenia d. Essential thrombocythemia

*b. Thrombocytosis This platelet count is elevated, so the correct terminology to describe it is thrombocytosis; this is most probably a reactive thrombocytosis. Platelets are also elevated in essential thrombocythemia, but they usually exceed 1 million/mL (1000 × 10^9/L), and other abnormalities would also be seen in the CBC.

What is the most serious clinical consequence of heparin-induced thrombocytopenia? a. Hemorrhage b. Thrombosis c. Factor XII activation d. Resistance to aspirin therapy

*b. Thrombosis Patients with heparin-induced thrombocytopenia develop thrombotic problems. Patients who develop heparin-induced thrombocytopenia should be removed from heparin therapy as soon as the diagnosis is made, because continued heparin therapy can lead to significant morbidity and mortality. After discontinuation of heparin, the platelet count begins to rise and should return to normal within a few days.

A 35-year-old woman with neurologic symptoms presents with a markedly decreased platelet count. She has moderate anemia with many red cell fragments on the blood film, as well as polychromasia and nucleated red blood cells (RBCs). The prothrombin time (PT) and partial thromboplastin time (PTT) are both normal. Which is the most likely diagnosis? a. Immune thrombocytopenic purpura b. Thrombotic thrombocytopenic purpura c. Hemolytic uremic syndrome d. DIC

*b. Thrombotic thrombocytopenic purpura Thrombotic thrombocytopenic purpura is characterized by thrombocytopenia, a microangiopathic hemolytic anemia with schistocytes (red cell fragments), and neurologic abnormalities. It is most common in women 30 to 40 years of age.

All are often associated with thrombocytosis except: a. hemorrhage. b. alcoholic liver disease. c. iron deficiency. d. inflammation.

*b. alcoholic liver disease. The only condition listed that is not associated with reactive thrombocytosis is alcoholic liver disease.

Which patient group is most commonly diagnosed with acute immune thrombocytopenic purpura? a. Older men after an infection b. Infants born to women who had eclampsia c. Children after having an infection d. Adult patients with enlarged spleens

*c. Children after having an infection Acute immune thrombocytopenic purpura is primarily a disorder of children. It frequently occurs 1 to 3 weeks after an infection.

What is the most common infectious cause of congenital neonatal megakaryocytic hypoplasia? a. Epstein-Barr virus b. Human immunodeficiency virus (HIV) c. Cytomegalovirus d. Rubella

*c. Cytomegalovirus Cytomegalovirus is the most common infectious agent causing congenital neonatal megakaryocytic hypoplasia. Cytomegalovirus appears to inhibit megakaryocytes and their precursors, resulting in impaired platelet production.

A 4-year-old child becomes very sick after drinking contaminated water. Kidney function tests are markedly elevated. Thrombocytopenia is mild, and a few schistocytes are noted on the blood film. Which is most likely the diagnosis? a. Immune thrombocytopenic purpura b. Thrombotic thrombocytopenic purpura c. Hemolytic uremic syndrome d. DIC

*c. Hemolytic uremic syndrome Hemolytic uremic syndrome is found primarily in children between the ages of 6 months to 4 years. In outbreaks of HUS associated with consumption of E. coli-contaminated water, both children and adults have developed HUS.

A 23-year-old man is brought by helicopter to a major trauma center after a severe motorcycle accident. He has major abdominal trauma, including a ruptured spleen, and is taken to surgery, where his spleen is removed. Two weeks after surgery, his platelet count peaks at 950 × 10^9/L. What is the most likely cause for this high platelet count? a. Reactive thrombocytosis secondary to trauma b. Essential thrombocythemia c. Postsplenectomy thrombocytosis d. Reactive thrombocytosis secondary to acute blood loss

*c. Postsplenectomy thrombocytosis Removal of the spleen characteristically results in a thrombocytosis that can reach or even exceed 1000 × 10^9/L (1 million/mL). The platelet count usually peaks 1 to 3 weeks after surgery and generally remains elevated for 1 to 3 months. Platelet counts generally are not this elevated in reactive thrombocytosis, and they do not peak 2 to 3 weeks after surgery.

Which is an example of a quantitative platelet disorder related to distribution? a. Thrombotic cytopenic purpura b. Essential thrombocythemia c. Splenomegaly d. Hemolytic uremic syndrome

*c. Splenomegaly An abnormal distribution of platelets may cause thrombocytopenia. The spleen sequesters approximately one-third of the total platelet mass. When the spleen is enlarged (splenomegaly), most platelets are sequestered in the enlarged spleen, resulting in a lower venous blood count.

What is the single most common cause of clinically important bleeding? a. Hemophilia b. Fibrinogen deficiency c. Thrombocytopenia d. Qualitative platelet disorders

*c. Thrombocytopenia The single most common cause of clinically important bleeding is thrombocytopenia with a platelet count less than 100 × 10^9/L.

What are the primary clinical manifestations of essential thrombocythemia? a. Platelet dysfunction b. Hemorrhage c. Thrombosis d. All of the options

*d. All of the options Patients with essential thrombocythemia have platelet dysfunction and may either bleed or experience thrombosis.

Which factor does the Coppo score consider in thrombotic thrombocytopenic purpura? a. Creatinine levels b. Platelets counts c. Antinuclear antibodies d. All of the options

*d. All of the options The score described by Coppo, which considers creatinine levels, platelet counts, and the presence of antinuclear antibodies, offers high positive predictive values and specificity, but low sensitivity in TTP.

Which is a commonly used drug that can cause thrombocytopenia? a. Warfarin b. Aspirin c. Ibuprofen d. Heparin

*d. Heparin Heparin is associated with drug-induced thrombocytopenia; this is called heparin-induced thrombocytopenia, and it can have serious thrombotic complications. Warfarin does not affect the platelet count. Aspirin and ibuprofen both affect platelet function.

Which results in ineffective thrombopoiesis? a. Immune thrombocytopenic purpura b. Thrombotic thrombocytopenic purpura c. Disseminated intravascular coagulation (DIC) d. Megaloblastic anemia

*d. Megaloblastic anemia Thrombocytopenia because of ineffective thrombopoiesis is one of the usual features of megaloblastic anemias. Vitamin B12 and folic acid are both required for normal maturation of megakaryocytes in the bone marrow.

What is believed to be the cause for acute immune thrombocytopenia purpura in children? a. Development of a platelet-specific autoantibody b. Development of a white cell autoantibody that cross-reacts with platelet membrane antigens c. Development of an allogeneic antibody after transfusion of random allogeneic platelets d. Nonspecific binding of immune complexes to the platelet membrane after a viral illness

*d. Nonspecific binding of immune complexes to the platelet membrane after a viral illness Acute immune thrombocytopenia purpura in children often follows a viral illness. This suggests that some children produce antibodies and immune complexes against viral antigens and that platelet destruction may result from their binding to the platelet membrane.

Which is successfully treated with therapeutic plasma exchange? a. Immune thrombocytopenic purpura b. Chronic DIC c. Acute DIC d. Thrombotic thrombocytopenic purpura

*d. Thrombotic thrombocytopenic purpura The most effective treatment for thrombotic thrombocytopenic purpura is therapeutic plasma exchange using fresh frozen plasma. Dramatic effects may be seen within just a few hours.

The terms petechiae, purpura, and ecchymoses all describe: a. varying degrees of thrombocytopenia. b. varying degrees of thrombocythemia. c. varying qualitative platelet disorders. d. varying size hemorrhages into the skin because of small vessel bleeding.

*d. varying size hemorrhages into the skin because of small vessel bleeding. These terms all refer to small-vessel bleeding into the skin that is caused by thrombocytopenia or many of the qualitative platelet disorders. Petechiae are small pinpoint hemorrhages, purpura are about 1 cm in diameter, whereas ecchymoses are 3 cm or larger.