Hereditary spherocytosis overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Hereditary spherocytosis is a genetically-transmitted form of spherocytosis, an auto-hemolytic anemia characterized by the production of red blood cells that are sphere-shaped rather than donut-shaped, and therefore more prone to hemolysis.
Historical Perspective
- Towards the end of the nineteenth century Vanlair and Masius described the case of a young woman who developed icterus, recurrent attacks of left upper quadrant abdominal pain and splenomegaly shortly after giving birth. The stools were not light coloured, but rather deeply pigmented. The patient's mother and sister were also icteric, and the sister's spleenwas enlarged.
Classification
- Hereditary Spherocytosis classified on basis of underlying defect in protein and also on the basis of severity of hemolysis.
Pathophysiology
There is intrinsic defects in erythrocyte membrane proteins that result in RBC cytoskeleton instability. Loss of erythrocyte surface area leads to the spherical shape of RBCs (spherocytes), which are culled rapidly from the circulation by the spleen. Hemolysis mainly confined to the spleen and, therefore, is extravascular. Splenomegaly commonly develops.
The following four abnormalities in RBC membrane proteins have been identified in HS:
- Spectrin deficiency alone
- Combined spectrin and ankyrin deficiency
- Band 3 deficiency
- Protein 4.2 defects
Causes
- HS is caused by a variety of mutations that lead to defects in red blood cell (RBC) membrane proteins. HS usually is transmitted as an autosomal dominant trait, and the identification of the disorder in multiple generations of affected families is the rule. Homozygosity for this dominantly transmitted HS gene has not been identified, which suggests that the homozygous state is incompatible with life.
Differentiating Hereditary spherocytosis overview from Other Diseases
Epidemiology and Demographics
- HS is seen in all populations but appears to be especially common in people of northern European ancestry.
- In the United States, the incidence of the disorder is approximately one case in 5000 people.
- In northern European, HS affects as many as 1 in 2000 to 1 in 5000 (prevalence, approximately 0.02 to 0.05 percent).