Spherocytosis

Spherocytes are small, spherical red blood cells (RBC). Spherocytes are approximately two-thirds the diameter of normal red blood cells (RBC). Hereditary spherocytosis (HS) is a form of hemolytic anemia characterized by spectrin deficiency, a disorder of red cell shape causing increased fragility. Spectrin is a large cytoskeletal protein that is found on the inner cell membrane of red blood cells and that functions especially in maintaining cell shape. In Golden Retrievers pedigree analysis reveals autosomal dominant inheritance.

Hereditary spherocytosis results in hemolytic anemia and enlarged spleen (splenomegaly). An intrinsic genetic defect causes defects in membrane proteins. Most cases of HS are heterozygous because homozygous states are lethal.

Anemia usually is mild to moderate; however, sometimes it is very severe and sometimes it is not present. Splenomegaly is the rule, and palpable spleens have been detected most individuals. Severe hemolytic anemia requires red cell transfusions. Possible complications include development of gallstones from the pigment that comes from the destroyed red blood cells.

Affected individuals may have yellowing of the skin and eyes (jaundice) and pale mucous membranes.

After the spleen is removed, the life span of the red blood cell returns to normal. Although the abnormal cell defect continues, the red blood cell life span returns to normal. In mild cases discovered in adults, splenectomy may not be necessary.

Causes of Non-hereditary Spherocytosis

Non-hereditary (acquired spherocytosis) also can be caused by:

• Genetic mutations
• Nutritional deficiencies (diabetic animals)
• Toxins such as onions (most species), acetaminophen, methylene blue, daily intravenous injections of propofol (cats), and phenothiazines and dried red maple leaves (horses)
• Trauma to red blood cells

Because this is an inherited disorder it may not be prevented.

References

1. Slappendel RJ, van Zwieten R, van Leeuwen M, Schneijdenberg CT. Hereditary spectrin deficiency in Golden Retriever dogs. J Vet Intern Med. 2005 Mar-Apr;19(2):187-92
2. Congenital spherocytic anemia. MedlinePlus
3. Gailene Holland, DVM; Paula M. Krimer, DVM, DVSc; Bruce E. LeRoy, DVM, PhD; and Kenneth S. Latimer, DVM, PhD. Spherocytosis: A Brief Overview. College of Veterinary Medicine University of Georgia, Athens, GA