Deck 17: Hemolytic Anemia: Membrane Defects

Question 1

What is the principal confirmation test in the diagnosis of HS?

A) Erythrocyte indices
B) Erythrocyte survival test
C) Osmotic fragility test
D) Hemoglobin electrophoresis

Answer 1

Osmotic fragility test

Question 2

Which of the following tests is used to screen for PNH?

A) Immunophenotyping
B) Sugar-water test
C) Acidified serum test
D) All of the above

Answer 2

Sugar-water test

Question 3

Which of the following statements best describes the function of DAF in the body?

A) Facilitates the amplification of the complement cascade by activating C3 convertase
B) Prevents the amplification of C3/C5 convertase activity
C) Facilitates complement binding on erythrocytes
D) Prevents apoptosis of erythrocyte precursors

Answer 3

Prevents the amplification of C3/C5 convertase activity

Question 4

A defect in ankyrin is described as:

A) A vertical interaction defect
B) A horizontal interaction defect
C) Both vertical and horizontal interaction defects
D) Cannot be determined

Question 5

Select the best statement from the following choices to describe the pathogenesis of PNH.

A) Increased hemolytic episodes are produced as a result of complement binding to erythrocytes via IgG antibodies in cold temperatures.
B) Increased hemolytic episodes are produced as a result of missing cell membrane proteins that regulate complement activation.
C) Increased hemolytic episodes are produced as a result of missing enzymes necessary for ATP production in erythrocytes.
D) Increased hemolytic episodes are produced as a result of initiation of an immune response against erythrocytes.

Question 6

PNH is currently confirmed in the lab by which of the following?

A) Immunophenotyping
B) Ham and sucrose lysis tests
C) Donath-Landsteiner test
D) Osmotic fragility

Question 7

Paroxysmal nocturnal hemoglobinuria has four basic disease mechanisms: hyperhemolysis, venous thrombosis, infection, and bone marrow hypoplasia. Which of these mechanisms is the most severe complication?

A) Hyperhemolysis
B) Infection
C) Venous thrombosis
D) Bone marrow hypoplasia

Question 8

Which of the following disorders is characterized by both a deficiency in spectrin and the presence of a mutant spectrin protein?

A) HPP
B) HE
C) HS
D) Acanthocytosis

Question 9

A 5-year-old boy is admitted to the pediatric unit with a fractured tibia. Routine blood work is ordered. His PB smear shows moderate spherocytosis. An osmotic fragility is also ordered, and the test result indicates an increased osmotic fragility. Based on these findings, what is the most likely defect?

A) Hereditary elliptocytosis
B) Hereditary spherocytosis
C) Microangiopathic hemolytic anemia from trauma
D) Cold autoimmune hemolytic anemia

Question 10

The SAO variant of HE is associated with:

A) Defective pectrin tetramer formation
B) Defective protein 4.1
C) Defective band 3 protein and abnormally tight binding to ankyrin
D) All of the above

Question 11

Which of the following subtypes of PNH is characterized by moderate hemolysis and intermediate GPI expression?

A) Type I
B) Type II
C) Type III
D) Cannot be determined based on the information given

Question 12

Which of the following sets of disorders is characterized by increased osmotic fragility?

A) HE and PNH
B) HS and hereditary overhydrated stomatocytosis
C) HS and hereditary dehydrated stomatocytosis
D) HS and thalassemia

Question 13

Defects in integral proteins, band 4.1, and spectrin are associated with which of the following disorders?

A) HS
B) HE
C) Acanthocytosis
D) PNH

Question 14

Which of the following disorders is caused by abnormal permeability of the RBC membrane?

A) Hereditary elliptocytosis
B) Hereditary spherocytosis
C) PNH
D) Hereditary dehydrated stomatocytosis

Question 15

The laboratory professional notes about 20% spherocytes on a peripheral blood smear of a 4-year-old boy. An osmotic fragility test is performed. The control shows initial hemolysis at 0.50% NaCl and complete hemolysis at 0.35% NaCl. The patient sample has initial hemolysis 0.60% NaCl and complete hemolysis at 0.45% NaCl. What does this indicate?

A) The patient is exhibiting increased osmotic fragility.
B) The patient has AIHA.
C) The patient is not exhibiting decreased osmotic fragility.
D) The control is erroneous, so patient results are invalid.

Question 16

Which of the following disorders has an abnormal erythrocyte membrane that is abnormally permeable, resulting in the loss of K+ and water and decreased deformability?

A) Overhydrated hereditary stomatocytosis
B) Dehydrated hereditary stomatocytosis
C) Hereditary elliptocytosis
D) Hereditary spherocytosis

Question 17

Which of the following causes horizontal interactions of skeletal protein abnormalities?

A) Ankyrin
B) Glycophorin C
C) Band 3
D) Protein 4.2

Question 18

Hereditary stomatocytosis is a condition resulting from defects in:

A) Cation permeability
B) Spectrin
C) Protein 4.1
D) Spectrin dimer-dimer association

Question 19

In hereditary spherocytosis, the erythrocytes become trapped in the splenic cords and run out of ATP to pump out excessive ions. What is the ion involved?

A) K+
B) Chloride
C) Na+
D) Oxygen

Question 20

A sample has the following test results: hemoglobin 9 g/dL, autohemolysis increased after 48 hours, and increased hemolysis observed with the Ham test and sucrose hemolysis test. Based on these findings, what is the patient most likely suffering from?

A) HS
B) HE
C) PNH
D) PCH

Question 21

Laboratory findings on a stained blood smear exhibit striking erythrocyte morphologic abnormalities. The MCV is decreased, osmotic fragility is abnormal, and the thermal sensitivity test demonstrates an increase in erythrocyte fragmentation. Autohemolysis in increased and is not corrected with glucose. What disorder is associated with these findings?

A) Hereditary pyropoikilocytosis
B) Hereditary stomatocytosis
C) PNH
D) Hereditary spherocytosis

Question 22

Complete the following table:

Question 23

Which of the following disorders is characterized by increased erythrocyte membrane sphingomyelin and decreased lecithin?

A) HS
B) HE
C) Acanthocytosis
D) HPP

Question 24

In PNH, cells are susceptible to complement-induced lysis. This is thought to result from the lack of what two regulating factors?

A) LCAT and lipoprotein
B) DAF and MIRL
C) HDL and VLDL
D) Beta and alpha lipoprotein

Question 25

Mary, a 7-year-old, was admitted to the hospital after experiencing severe anemia following a respiratory infection. Her father has a history of RBC membrane abnormality and recently underwent a splenectomy to help alleviate the problem. Upon examination, it was revealed that Mary had hepatosplenomegaly and slight bruising on her forearms. A CBC was ordered, with the following results: HGB 10.8 g/dL
HCT 29.2%
WBC 11 × 10⁹/L
RBC 3.8 × 10¹²/L
MCV 77 fl
MCH 28 pg
MCHC 37%
PLT 275 × 10⁹/L
Peripheral smear: moderate polychromasia and spherocytes
Which of the following is most consistent with a presumptive diagnosis in this case?

A) PNH
B) HS
C) DHS
D) HE

Question 26

Explain why patients with HS typically have an MCHC >36%.

Question 27

Which of these disorders has a defective vertical protein interaction between RBC skeleton and the membrane?

A) Hereditary elliptocytosis
B) Hereditary pyropoikilocytosis
C) Hereditary spherocytosis
D) Acanthocytosis

Question 28

The function of the MIRL is to:

A) Induce red cell agglutination
B) Prevent activation of C3b converting enzyme
C) Interfere with C8/C9 activation
D) All of the above

Question 29

The characteristic "fish-mouth" central pallor seen in overhydrated hereditary stomatocytosis is caused by an excessive influx of what in the RBCs?

A) Potassium
B) Chloride
C) Sodium and water
D) Sodium

Question 30

The screening sucrose hemolysis (sugar-water) test is useful in identifying PNH cells by what mechanism?

A) Immunophenotyping
B) Hemoglobin electrophoresis
C) Erythrocyte survival test
D) Complement lysis

Question 31

Explain how a somatic mutation in the PIGA gene leads to PNH.

Question 32

Immunophenotyping is performed on a patient suspected of having PNH. What monoclonal antibody specificity should be ordered?

A) CD33 and CD13
B) CD56 and CD4
C) CD3 and CD8
D) CD55 and CD59

Question 33

A patient is suspected of having HS. However, there appear to be <1% spherocytes on the peripheral blood smear, and the osmotic fragility test is normal. What test could be performed to increase the sensitivity of testing for HS?

A) Incubated osmotic fragility test
B) Immunophenotyping for CD55 and CD59
C) Sucrose hemolysis test
D) Ham test

Question 34

Explain why patients with HS sometimes suffer from gallstones.

Question 35

Hereditary pyropoikilocytosis differs in red cell morphology from other erythrocyte membrane defects by what characteristic cell shape?

A) Spherocyte
B) Elliptocyte
C) Schistocyte
D) Target cell

Question 36

Differentiate between the three different subtypes of HE based on PB smear morphology.