Beta thalassemias (β thalassemias) are a group of inherited blood disorders. They are forms of thalassemia caused by reduced or absent synthesis of the beta chains of hemoglobin that result in variable outcomes ranging from severe anemia to clinically asymptomatic individuals. Global annual incidence is estimated at one in 100,000. Beta thalassemias occur due to malfunctions in the hemoglobin subunit beta or HBB. The severity of the disease depends on the nature of the mutation.HBB blockage over time leads to decreased beta-chain synthesis. The bodys inability to construct new beta-chains leads to the underproduction of HbA (adult hemoglobin). Reductions in HbA available overall to fill the red blood cells in turn leads to microcytic anemia. Microcytic anemia ultimately develops in respect to inadequate HBB protein for sufficient red blood cell functioning. Due to this factor, the patient may require blood transfusions to make up for the blockage in the beta-chains. Repeated blood transfusions cause severe problems associated with iron overload. Signs and symptoms
Three main forms have been described: thalassemia minor, thalassemia intermedia, and thalassemia major which vary from asymptomatic or mild symptoms to severe anemia requiring lifelong transfusions. Individuals with beta thalassemia major (those who are homozygous for thalassemia mutations, or inheriting 2 mutations) usually present within the first two years of life with symptomatic severe anemia, poor growth, and skeletal abnormalities. Untreated thalassemia major eventually leads to death, usually by heart failure; therefore, prenatal screening is very important.
Screening has shown reduced incidence; by 1995 the prevalence in Italy reduced from 1:250 to 1:4000, and a 95% decrease in that region. The decrease in incidence has benefitted those affected with thalassemia, as the demand for blood has decreased, therefore improving the supply of treatment. Treatment
Beta thalassemia major
Affected children require regular lifelong blood transfusions. Bone marrow transplants can be curative for some children. Patients receive frequent blood transfusions that lead to or potentiate iron overload. Iron chelation treatment is necessary to prevent damage to internal organs in cases of iron overload. Advances in iron chelation treatments allow patients with thalassemia major to live long lives with access to proper treatment. Popular chelators include deferoxamine and deferiprone.The oral chelator deferasirox was approved for use in 2005 in some countries. Bone marrow transplantation is the only cure and is indicated for patients with severe thalassemia major. Transplantation can eliminate a patients dependence on transfusions. Absent a matching donor, a savior sibling can be conceived by preimplantation genetic diagnosis (PGD) to be free of the disease as well as to match the recipients human leukocyte antigen (HLA) type.Serum ferritin (the storage form of iron) is routinely measured in those with beta thalassemia to determine the degree of iron overload; with increased ferritin levels directing the use of iron chelation therapy.