Support Hereditary Spherocytosis

What is Hereditary Spherocytosis?
Hereditary Spherocytic Hemolytic Anemia is a rare blood disorder characterized by defects within red blood cells (intracorpuscular) that result in a shortened survival time for these cells. Red blood cells (erythrocytes) normally circulate for a few months and when they die off are replaced by new erythrocytes. However, in Hereditary Spherocytic Hemolytic Anemia, the cells die prematurely. They also have low amounts of fats (lipid) in the cell membranes and an abnormally small amount of surface area. The red blood cells are sphere shaped (spherocytic) making it difficult for them to pass through the spleen, resulting in the early destruction of these cells (hemolysis). The sphere shape of the red blood cells is the hallmark of Hereditary Spherocytic Hemolytic Anemia, and this abnormality may be identified under a microscope. Hereditary Spherocytic Hemolytic Anemia is caused by an inherited metabolic defect.

Symptoms
Hereditary Spherocytic Hemolytic Anemia may be present at birth or may not become apparent for years. The symptoms of this disorder vary greatly from one person to another. In many people the symptoms are so mild that the disease is not diagnosed. Symptoms of Hereditary Spherocytic Hemolytic Anemia may include excessive tiredness and a moderate persistent yellow appearance to the skin (jaundice). The onset of puberty may be delayed in children with Hereditary Spherocytic Hemolytic Anemia. Some children may experience abdominal discomfort and have an abnormally enlarged spleen (splenomegaly). An infection is the most common cause of the temporary failure of the bone marrow to produce blood components (aplastic crisis) in people with Hereditary Spherocytic Hemolytic Anemia. This crisis results in a temporary deficiency of red blood cell production. Trauma or pregnancy may make the aplastic crisis worse. Symptoms of an aplastic crisis may include fever, headache, abdominal pain, profound loss of appetite (anorexia), vomiting, and fatigue. Children who are experiencing an aplastic crisis may also have nose bleeds (epistaxis). Occasionally children with Hereditary Spherocytic Hemolytic Anemia have an abnormally enlarged liver (hepatomegaly), stones in the gall bladder (cholelithiasis), and/or leg ulcers. In some cases deformities of the anatomy are present at birth and may include more than the normal number of fingers and/or toes (polydactylism), and/or a "tower-shaped" skull. Hemolytic Anemias, including Hereditary Spherocytic Hemolytic Anemia, have two distinct laboratory findings: a reduction in the life span of red blood cells and the retention of iron within the body particularly in those cells that have the ability to dispose of wastes and toxins (reticuloendothelial system or RES). In all hemolytic anemias, there is excessive destruction of red blood cells.

CAUSES
Hereditary Spherocytic Hemolytic Anemia is an inborn error of metabolism that can be inherited as an autosomal dominant or autosomal recessive genetic trait. Human traits, including the classic genetic diseases, are the product of the interaction of two genes, one received from the father and one from the mother. In dominant disorders, a single copy of the disease gene (received from either the mother or father) will be expressed "dominating" the other normal gene and resulting in the appearance of the disease. The risk of transmitting the disorder from affected parent to offspring is 50 percent for each pregnancy regardless of the sex of the resulting child.

The more severe forms of Hereditary Spherocytic Hemolytic Anemia are inherited as autosomal recessive genetic traits. In recessive disorders, the condition does not appear unless a person inherits the same defective gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk of transmitting the disease to the children of a couple, both of whom are carriers for a recessive disorder, is 25 percent. Fifty percent of their children risk being carriers of the disease, but generally will not show symptoms of the disorder. Twenty-five percent of their children may receive both normal genes, one from each parent, and will be genetically normal (for that particular trait). The risk is the same for each pregnancy.

Usually people with Hereditary Spherocytic Hemolytic Anemia have a family history of anemia, jaundice, or spleen enlargement (splenomegaly). At times, other family members can be identified with this disorder, but in other cases people with Hereditary Spherocytic Hemolytic Anemia may have no family history of the disorder that can be traced.

The symptoms of Hereditary Spherocytic Hemolytic Anemia develop due to the abnormality of the red blood cell membrane. The defective gene that causes Hereditary Spherocytic Hemolytic Anemia is located on the short arm of chromosome 8.

AFFECTED POPULATION
Hereditary Spherocytic Hemolytic Anemia is a rare disorder that affects males and females in equal numbers. This disorder occurs most frequently in people of Northern European heritage with a prevalence of approximately 1 in 5,000 people. However, this disorder also occurs in other populations at a lower prevalence rate.