Spherocytosis

Spherocytosis is an auto-hemolytic anemia (a disease of the blood) characterized by the production of red blood cells (RBCs), or erythrocytes, that are sphere-shaped, rather than donut-shaped. It is caused by a molecular defect in one or more of the proteins of the red blood cell cytoskeleton (usually ankyrin, sometimes spectrin). Because the cell skeleton has a defect, the blood cell contracts to its most surface-tension efficient and least flexible configuration, a sphere, rather than the more flexible donut-shape. more...

The sphere-shaped red blood cells are known as spherocytes.

Though the spherocytes have a smaller surface area through which which oxygen and carbon dioxide can be exchanged, they in themselves perform adequately to maintain healthy oxygen supplies. However, they have a high osmotic fragility--when placed into water, they are likely to burst. These cells are more prone to physical degradation. They are most commonly found in immunologically-mediated hemolytic anemias and in hereditary spherocytosis, but the former would have a positive direct Coombs antibody test and the latter would not. The misshapen but otherwise healthy red blood cells are mistaken by the spleen for old or damaged red blood cells and it thus constantly breaks them down, causing a cycle whereby the body destroys its own blood supply (auto-hemolysis).

Symptoms

The spleen's hemolysis results directly in varying degrees of anemia and hyperbilirubinemia, which in turn result in symptoms of fatigue, pallor, and jaundice.

Acute cases can threaten hypoxemia through anemia and acute kernicterus through hyperbilirubinemia, particularly in newborns.

Chronic symptoms include anemia and splenomegaly, or enlargement of the spleen due to its increased activity. Furthermore, the detritus of the broken-down blood cells--bilirubin--accumulates in the gallbladder, and can cause gallstones or "sludge" to develop. In chronic patients, an infection or other illness can cause an increase in the destruction of red blood cells, resulting in the appearance of acute symptoms, a hemolytic crisis.

Diagnosis

In peripheral blood smears, many of the red blood cells will appear abnormally small and will lack the central pallor--the lighter area in the middle of a RBC as seen under a microscope.

The splenic cords are congested with red blood cells to be destroyed and macrophages of the spleen will show signs of actively destroying erythrocytes (erythrophagocytosis). This will result in elevated bilirubin counts.

The bone marrow in its role of manufacturing red blood cells will display hyperplasia, the increased activity of replacing RBCs. As a result, immature red blood cell--or reticulocyte--counts will appear elevated.

Treatment

Treatment of acute symptoms

Acute symptoms of anemia and hyperbilirubinemia can indicate treatment with blood transfusions or exchanges. Transfusions treat anemia by adding healthy donor blood to the patient's own, providing needed red blood cells. As the transfused blood does not contain elliptocytes, it will not be hemolysed per se, but the overactive spleen may still break down a significant proportion of the transfused blood. Exchanges treat hyperbilirubinemia by replacing some portion of the patient's blood with healthy donor blood, thus removing some portion of the toxic bilirubin.

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