The nurse explains to the parents of a 1-year-old child admitted to the hospital in a sickle cell crisis that the local tissue damage the child has on admission is caused by which of the following?
A. Autoimmune reaction complicated by hypoxia.
B. Lack of oxygen in the red blood cells.
C. Obstruction to circulation.
D. Elevated serum bilirubin concentration.
Correct Answer: C. Obstruction to circulation
Characteristic sickle cells tend to cause “log jams” in capillaries. This results in poor circulation to local tissues, leading to ischemia and necrosis. Red blood cells become more rigid. There is a release of adhesion molecules, causing interaction of this deformed, sickled RBC to the endothelium. This increased adhesion of erythrocytes followed by the formation of heterocellular aggregates physically causes small vessel occlusion and resultant local hypoxia.
Option A: Sickle cell disease is an inherited disease, not an autoimmune reaction. Sickle cell disease is an autosomal recessive disorder of a gene mutation. On chromosome 11, nucleotide mutation leads to substitution of glutamic acid to valine at position six on the beta-globin subunit. This leads to changes in the physical properties of the globin chain.
Option B: The basic defect in sickle cell disease is an abnormality in the structure of RBCs. The erythrocytes are sickle-shaped, rough in texture, and rigid. Red blood cells with normal hemoglobin are smooth, disk-shaped, and flexible, like doughnuts without holes. They can move through the blood vessels easily. Cells with sickle cell hemoglobin are stiff and sticky. When they lose their oxygen, they form into the shape of a sickle or crescent, like the letter C.
Option D: Elevated serum bilirubin concentrations are associated with jaundice, not sickle cell disease. Sickle cell crisis patient evaluation warrants routine laboratory examination such as CBC with differential, a reticulocyte count, and a complete metabolic panel including liver function tests.
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