Extrinsic Defects Leading to Increased Erythrocyte Destruction— Nonimmune Causes

Question 1

1. Which one of the following is a feature found in all microangiopathic hemolytic anemias?
   a. Pancytopenia
   b. Thrombocytosis
   c. Intravascular RBC fragmentation
   d. Prolonged prothrombin time and partial thromboplastin
   time

Answer 1

c. Intravascular RBC fragmentation

Question 2

2. Typical laboratory findings in TTP and HUS include:
   a. Schistocytosis and thrombocytopenia
   b. Anemia and reticulocytopenia
   c. Reduced levels of lactate dehydrogenase and aspartate
   aminotransferase
   d. Increased levels of free plasma hemoglobin and serum
   haptoglobin

Answer 2

a. Schistocytosis and thrombocytopenia

Question 3

3. The pathophysiology of idiopathic TTP involves:
   a. Shiga toxin damage to endothelial cells and obstruction
   of small blood vessels in glomeruli
   b. Formation of platelet-VWF thrombi due to autoantibody
   inhibition of ADAMTS-13
   c. Overactivation of the complement system and endothelial cell damage due to loss of regulatory function
   d. Activation of the coagulation and fibrinolytic systems
   with fibrin clots throughout the microvasculature

Answer 3

b. Formation of platelet-VWF thrombi due to autoantibody
inhibition of ADAMTS-13

Question 4

4. Which of the following tests yields results that are abnormal
   in DIC but are usually within the reference interval or just
   slightly abnormal in TTP and HUS?
   a. Indirect serum bilirubin and serum haptoglobin
   b. Prothrombin time and partial thromboplastin time
   c. Lactate dehydrogenase and aspartate aminotransferase
   d. Serum creatinine and serum total protein

Answer 4

b. Prothrombin time and partial thromboplastin time

Question 5

5. Which one of the following laboratory results may be seen
   in BOTH traumatic cardiac hemolytic anemia and exerciseinduced hemoglobinuria?
   a. Schistocytes on the peripheral blood film
   b. Thrombocytopenia
   c. Decreased serum haptoglobin
   d. Hemosiderinuria

Answer 5

c. Decreased serum haptoglobin

Question 6

6. Which of the following species of Plasmodium produce hypnozoites that can remain dormant in the liver and cause a
   relapse months or years later?
   a. P. falciparum
   b. P. vivax
   c. P. knowlesi
   d. P. malariae

Answer 6

b. P. vivax

Question 7

7. Which one of the following is not a mechanism causing
   anemia in P. falciparum infections?
   a. Inhibition of erythropoiesis
   b. Lysis of infected RBCs during schizogony
   c. Competition for vitamin B12 in the erythrocyte
   d. Immune destruction of noninfected RBCs in the spleen

Answer 7

c. Competition for vitamin B12 in the erythrocyte

Question 8

8. Which Plasmodium species is widespread in Malaysia, has
   RBCs with multiple ring forms, has band-shaped early trophozoites, shows a 24-hour erythrocytic cycle, and can
   cause severe disease and high parasitemia?
   a. P. falciparum
   b. P. vivax
   c. P. knowlesi
   d. P. malariae

Answer 8

c. P. knowlesi

Question 9

9. One week after returning from a vacation in Rhode Island, a
   60-year-old man experienced fever, chills, nausea, muscle
   aches, and fatigue of 2 days’ duration. A complete blood
   count (CBC) showed a WBC count of 4.5 3 109/L, hemoglobin level of 10.5 g/dL, a platelet count of 134 3 109/L, and a
   reticulocyte count of 2.7%. The medical laboratory scientist
   noticed tiny ameboid ring forms in some of the RBCs and
   some tetrad forms in others. These findings suggest:
   a. Bartonellosis
   b. Malaria
   c. Babesiosis
   d. Clostridial sepsis

Answer 9

c. Babesiosis

Question 10

10. What RBC morphology is characteristically found within
    the first 24 hours following extensive burn injury?
    a. Macrocytosis and polychromasia
    b. Burr cells and crenated cells
    c. Howell-Jolly bodies and bite cells
    d. Schistocytes and microspherocytes

Answer 10

d. Schistocytes and microspherocytes

Question 11

11. A 36-year-old woman was brought to the emergency department by her husband because she had experienced a
    seizure. He reported that she had been well until that
    morning, when she complained of a sudden headache and
    malaise. She was not taking any medications and had no
    history of previous surgery or pregnancy. Laboratory studies showed a WBC count of 15 3 109/L, hemoglobin level
    of 7.8 g/dL, a platelet count of 18 3 109/L, and schistocytes
    and helmet cells on the peripheral blood film. Chemistry
    test results included markedly elevated serum lactate dehydrogenase activity and a slight increase in the level of total
    and indirect serum bilirubin. The urinalysis results were
    positive for protein and blood, but there were no RBCs in
    the urine sediment. Prothrombin time and partial thromboplastin time were within the reference interval. When
    the entire clinical and laboratory picture is considered,
    which of the following is the most likely diagnosis?
    a. HUS
    b. HELLP syndrome
    c. TTP
    d. Exercise-induced hemoglobinuria

Answer 11

c. TTP