Least implicated in the pathophysiology of sickle cell disease:

 # Which is least implicated in the pathophysiology of sickle cell disease? 

a. Neutrophils 

b. Nitric oxide 

c. Platelets and coagulation factors 

d. Free hemoglobin

The correct answer is C. Platelets and Coagulation factor.

The pathophysiologic processes that lead to sickle cell disease related complications result from a combination of hemolysis and vaso-occlusion. Hemolysis occurs as a result of repeated episodes of hemoglobin polymerization/depolymerization as sickle red blood cells pick up and release oxygen in the circulation. Red blood cell membranes become abnormal from this process and red blood cells have a shortened lifespan. 

Hemolysis can occur both chronically and during acute painful vaso-occlusive crises and also results in the release of substantial quantities of free hemoglobin into the vasculature. The consumption of significant quantities of nitric oxide (NO) by this resultant free ferrous hemoglobin,  in turn, leads to abnormal regulation in vascular homeostasis. Moreover, neutrophils play a key role in the tissue damage which occurs as both neutrophil numbers are increased and evidence suggests that they are abnormally activated and adherent. Likewise, as suggested by recent data sickle red cells induce adhesion of lymphocytes and monocytes to the endothelium such that these may contribute to the pathogenesis of vascular occlusion. Platelet activation also occurs in SCD but is least implicated among the given options.

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High risk during surgery:

 # Which of the following may constitute high-risk during surgery? 

a. β-Thalasemia minor 

b. Hb S homozygous 

c. Hb D Punjab

d. Hb E trait

 

The correct answer is B. Hb S homozygous.

Hb D Punjab and Hb D Los Angeles are having same biochemical structure (Glutamic acid is replaced by Lysine at 121 position in β chain). Heterozygous state is essentially asymptomatic. Homozygous Hb D is very rare. Sickle cell disease is relatively less associated with by Hb S/D Punjab/Los Angeles . Mutation in β chain by virtue of which glutamic acid is replaced by lysine at 26th position in β chain causes Hb E. In Hb E carrier state, 30–45% of the Hb is Hb E, and such carriers are asymptomatic but shows microcytosis. Homozygons E disease is associated with marked microcytosis and hypochromia, but the anemia is usually mild. Clinically resembles β-thalassemia minor. Hb E with Hb D heterozygous state is variable in severity.

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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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