Hereditary spherocytosis is a type of hemolytic anemia caused by a defect in the red blood cells (RBCs) membrane that become them fragile and vulnerable to the destruction in the spleen.
The normal shape of human RBCs, also called erythrocytes, is biconcave. The biconcave shape allows RBCs to bend and to flow through small blood vessels. In contrast, in hereditary spherocytosis, RBCs have a spherical or round shape. They are less deformable and break down more quickly than normal RBCs. Abnormal spherocytes become trapped and are usually destroyed in the spleen.
Hereditary spherocytosis is a genetic disorder caused by mutations in the genes that encoded the membrane proteins of RBCs.
The genes affected may be the following ones:
It is a hereditary disease passed down from parents to children. In some rare cases, spherocytosis is due to spontaneous mutation of the genes.
In 75% of the cases, it follows an autosomal dominant inheritance pattern, in 10% it is an autosomal recessive disorder and in 15% it is caused by a spontaneous mutation.
Hereditary spherocytosis incidence is about 1 in 5,000 people.
The most common symptoms of the disorder are:
In some cases, stress or vigorous exercise may narrow capillaries (tiny blood vessels) and lead to a massive destruction of RBCs over a short time called hemolytic crisis.
In a blood test, there will be a high percentage of defective RBCs (spherocytes).
Unconjugated or indirect bilirubin will have values between 1 to 4 mg/dl (mild unconjugated hyperbilirubinemia).
There is no specific treatment. In some patients who have severe anemia, splenectomy (surgical removal of the spleen) improves the anemia by removing the major site of red cell destruction. Splenectomy in children from 5 to 8 years of age or older may be needed for serious cases.
The spleen breaks down fragile RBCs and remove them from the bloodstream. When the spleen is removed, hemolysis (rupture of RBCs) will occur in other organs such as the liver but not in a massive and sudden way.
Splenectomy also prevents hemolytic crises.
Without a spleen, a person has an increased risk for some serious infections, particularly in children. For this reason, vaccinations and use of preventive antibiotics decrease this risk of infections.
Possible complications include: