Spherocytosis

Spherocytosis
Spherocytosis seen in a peripheral blood smear from a patient with hereditary spherocytosis

Spherocytosis is the presence in the blood of spherocytes, i.e erythrocytes (red blood cells) that are sphere-shaped rather than bi-concave disk shaped as normal. Spherocytes are found in all hemolytic anemias to some degree. Hereditary spherocytosis and autoimmune hemolytic anemia are characterized by having only spherocytes.[1]

Causes

Spherocytes are most commonly found in immunologically-mediated hemolytic anemias and in hereditary spherocytosis, but the former would have a positive direct Coombs 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). A complete blood count (CBC) may show increased reticulocytes, a sign of increased red blood cell production, and decreased hemoglobin and hematocrit. The term "non-hereditary spherocytosis" is occasionally used, albeit rarely.[2]

Lists of causes[3]:

Pathophysiology

Spherocytosis most often refers to hereditary spherocytosis. This is caused by a molecular defect in one or more of the proteins of the red blood cell cytoskeleton, including spectrin, ankyrin, Band 3, or Protein 4.2. Because the cell skeleton has a defect, the blood cell contracts to a sphere, which is its most surface tension efficient and least flexible configuration. Though the spherocytes have a smaller surface area through 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 more likely to burst than normal red blood cells. These cells are more prone to physical degradation.

Diagnosis

Spherocytosis can be diagnosed in Peripheral blood film by seeing spherical red blood cells rather than biconcave. Because Red blood cells are more prone to lysis in water (because the lack some proteins in their cytoskeleton) Osmotic Fragility test can also be helpful in the diagnosis.

See also

References

  1. ↑ Robert S. Hillman; Kenneth A. Ault; Henry M. Rinder (2005). Hematology in clinical practice: a guide to diagnosis and management. McGraw-Hill Professional. pp. 146–. ISBN 978-0-07-144035-6. Retrieved 15 November 2010.
  2. ↑ Thoma J, Kutter D, Casel S, et al. (2005). "HbSC hemoglobinopathy suspected by chest x-ray and red blood cell morphology". Acta Clin Belg. 60 (6): 377–82. doi:10.1179/acb.2005.057. PMID 16502600.
  3. ↑ Hirschmann, editors, Douglas C. Tkachuk, Jan V. (2007). Wintrobe's atlas of clinical hematology. Philadelphia, PA [etc.]: Lippincott Williams & Wilkins. ISBN 0781770238.
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