The duffy blood group system is functionally associated with:

# The duffy blood group system is functionally associated with:

a. Invasion by P. falciparum

b. Red cell urea transporter

c. Maintenance of membrane integrity

d. Invasion by P. vivax

The correct answer is: D. Invasion by P. vivax.

Duffy antigen is a receptor for Plasmodium vivax.

• The receptor for P. falciparum on RBCs are glycophorins

• Red cell urea transporter is the Kidd antigen and its absence can be associated with impaired urea transport and urine concentrating defect.

• Integral membrane proteins are band 3, glycophorins, Rh, Kell,  Kidd, Duffy and Lutheran glycoproteins. Though Duffy is an integral membrane protein but it is not the major protein involved in the overall integrity of RBC membrane.

• The peripheral membrane proteins are spectrin, ankyrin, actin, protein 4.1, 4.2 and 4.9, p 55 and the adducins.

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Howell–Jolly bodies contain

 # Howell–Jolly bodies contain: 

a. Iron 

b. DNA 

c. RNA 

d. Protein

The correct answer is B. DNA.

A Howell–Jolly body is a cytopathological finding of basophilic nuclear remnants (clusters of DNA) in circulating erythrocytes. During maturation in the bone marrow, late erythroblasts normally expel their nuclei; but, in some cases, a small portion of DNA remains.

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Pappenheimer bodies contain:

 # Pappenheimer bodies contain: 

a. Iron 

b. DNA 

c. RNA 

d. Ribosomal proteins

The correct answer is a. Iron.

Pappenheimer bodies are abnormal basophilic granules of iron found inside red blood cells on routine blood stain. They are a type of inclusion body composed of ferritin aggregates, or mitochondria or phagosomes containing aggregated ferritin.

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Membrane rigidity and fragility can be measured by:

 # Membrane rigidity and fragility can be measured by:

a. Osmocytometer

b. Spherocytometer

c. Ektacytometer

d. Viscometer

The correct answer is C. Ektacytometer. 

Osmotic gradient ektacytometry measures RBC deformability under a defined shear stress as a function of suspending medium osmolality. The test is used to evaluate for inherited RBC membrane disorders, which are commonly responsible for hemolytic anemia, differentiating among hereditary spherocytosis (HS), hereditary elliptocytosis (HE) and pyropoikilocytosis (HPP), Southeast Asian ovalocytosis (SAO) and hereditary stomatocytosis (HSt).

Osmotic Gradient Ektacytometry at Cincinnati Children's.Ektacytometry is recommended as the next step after hemoglobin electrophoresis in the diagnosis of a non-immune hemolytic anemia. An abnormal ektacytometry profile confirms a red cell membrane disorder and assists with the differential diagnosis between hereditary spherocytosis versus elliptocytosis / pyropoikilocytosis versus xerocytosis. This is particularly important in xerocytosis where splenectomy is contraindicated because it precipitously increases the risk for life-threatening thrombophilia. Ektacytometry in a patient with a non-transfusion dependent hemolytic anemia may save the need to perform a hereditary hemolytic anemia genetic panel. It can also help focus the genetic workup to a red cell membrane panel if ektacytometry is positive or to a red cell enzyme panel if ektacytometry is negative.

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Typical dominant HS is most commonly caused by deficiency of

 # Typical dominant HS is most commonly caused by deficiency of: 

a. Ankyrin 

b. Band 3 

c. Spectrin 

d. Protein 4.2

The correct answer is A. Ankyrin.

The most common cause of typical dominant HS (2/3rd of cases) is ankyrin defect. Band 3 defect and isolated spectrin deficiency is next common. The degree of spectrin deficiency correlates with spheroidicity, ability of red cells to withstand shear stress, degree of hemolysis and response to 

splenectomy. Protein 4.2 deficiency is inherited as autosomal recessive trait. Severe HS almost always have recessive inheritance and most have severe spectrin deficiency (< 40%) may be d/t defect in β-spectrin. 

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Decreased osmotic fragility is seen in:

 # Which of the following have decreased osmotic fragility? 

a. Hereditary spherocytosis 

b. Hereditary elliptocytosis 

c. Hereditary xerocytosis 

d. Hereditary stomatocytosis/hydrocytosis

The correct answer is C. Hereditary xerocytosis.

Osmotic fragility has been typically increased in Hereditary spherocytosis and hereditary  elliptocytosis. There are 2 types of hereditary stomatocytosis: hereditary xerocytosis (complex permeability defect d/t increased membrane lipids) and hereditary stomatocytosis – hydrocytosis (d/t deficiency of band 7.2b or stomatin). Both have autosomal dominant inheritance. Osmotic fragility is decreased in xerocytosis and increased in hydrocytosis. Xerocytosis may result in recurrent fetal loss, hydrops fetalis, neonatal hepatitis and familial pseudohyperkalemia.

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Major risk factor for venous thrombosis:

 Which of the following is a major risk factor for venous thrombosis?

a. Smoking

b. High cholesterol

c. Hypertension

d. Diabetes mellitus

e. Cancer

The correct answer is E. Cancer.

Venous thrombosis, including deep vein thrombosis and pulmonary embolism, occurs at an annual incidence of about 1 per 1000 adults. Rates increase sharply after around age 45 years, and are slightly higher in men than women in older age. Major risk factors for thrombosis, other than age, include exogenous factors such as surgery, hospitalization, immobility, trauma, pregnancy and the puerperium and hormone use, and endogenous factors such as cancer, obesity, and inherited and acquired disorders of hypercoagulation. 

Ref: Cushman M. Epidemiology and risk factors for venous thrombosis. Semin Hematol. 2007;44(2):62-69. doi:10.1053/j.seminhematol.2007.02.004

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