Beta-thalassemia

Other Names: Beta thalassemia major; Cooley's anemia; Beta thalassemia intermedia

Beta-thalassemia is a  that reduces the body's production of hemoglobin. Low levels of hemoglobin lead to a shortage of mature  and a lack of oxygen in the body

Genetics of beta thalassemia

There are two main forms of beta-thalassemia, classified based on the severity of symptoms:

• Thalassemia major (also called Cooley's anemia) - the more severe form, causing severe anemia and enlarged liver and spleen (hepatosplenomegaly) . This form usually becomes apparent before 2 years of age. If not treated, it causes failure to thrive and a shortened life expectancy.
• Thalassemia intermedia - the less severe form, becoming apparent later and causing milder anemia that does not require regular blood transfusions. People with this form are also at risk for iron overload.

Causes

Beta-thalassemia is caused by  in the HBB gene and is typically  in an  manner. This means that people with thalassemia major or thalassemia intermedia have a mutation in both of their copies of the HBB gene.

Delta Beta Thalassemia

People who have only one HBB gene mutation carriers typically are said to have thalassemia minor (or ) and usually do not have symptoms, but may have some symptoms of anemia.In some cases, anemia is worsened if there is a nutritional deficiency such as with iron, folic acid or vitamin B12.

Symptoms

People with beta-thalassemia have , which can cause paleness, weakness, fatigue, and more serious complications.

80%-99% of people have these symptoms

• Abnormal hemoglobin
• Microcytic
• Pallor
• Splenomegaly
• 30%-79% of people have these symptoms
• Abnormal skull morphology
• Abnormality of iron homeostasis
• Abnormality of temperature regulation
• Hepatomegaly
• Hypogonadotropic hypogonadism
• Reduced bone mineral density

5%-29% of people have these symptoms

• Cholelithiasis(Gallstones)
• Hepatitis(Liver inflammation)
• Hypertrophic (Enlarged and thickened heart muscle)
• Skin ulcer(Open skin sore)
• Low platelet count(Venous thrombosis)
• Blood clot in vein

Inheritance

Beta-thalassemia major and beta-thalassemia intermedia are usually inherited  in an autosomal recessive manner, which means both copies of the HBB gene  in each cell have mutations .

The parents of a person with an autosomal recessive condition each carry one copy of the mutated gene and are referred to as carriers. When two carriers have children, each child has a 25% (1 in 4) chance to be affected, a 50% (1 in 2) chance to be a carrier like each parent, and a 25% (1 in 4) chance to be unaffected and not a carrier. Sometimes, people with only one HBB gene mutation in each cell (carriers) do have mild . These people are said to have 'beta-thalassemia minor' or 'beta-thalassemia .

In a small percentage of families, the condition is inherited in an autosomal dominant manner. In these cases, one mutated copy of the gene in each cell is enough to cause the signs and symptoms of beta-thalassemia.

Treatment

Treatment involves regular transfusions and chelation therapy to reduce iron overload. Treatment allows for normal growth and development.Bone marrow transplantation or cord blood transplantation may eliminate the need for regular treatment.

The medication(s) listed below have been approved by the Food and Drug Administration (FDA) as orphan products for treatment of this condition

Thiotepa (Brand name: Tepadina)

To reduce the risk of graft rejection when used in conjunction with high-dose busulfan and cyclophosphamide as a preparative regimen for allogeneichematopoietic progenitor (stem)  transplantation (HSCT) for pediatric patients with class 3 beta-thalassemia.

NIH genetic and rare disease info

• NIH info on Beta-thalassemia

Beta-thalassemia is a rare disease.