Beta Thalassemia
Beta Thalassemia Causes
Mutations in the HBB gene cause beta thalassemia to develop. Hemoglobin consists of four protein subunits, with two subunits called alpha hemoglobin and two subunits called beta hemoglobin. The HBB gene provides instructions for making more beta hemoglobin. Some mutations in the HBB gene hinder the production of beta hemoglobin. The absence of beta hemoglobin is known as beta-zero (B0) thalassemia. With other HBB mutations, there may be production of some beta hemoglobin but in lower than normal amounts. A dicreased amount of beta hemoglobin is called beta-plus (B+) thalassemia. The loss of beta hemoglobin results to a diminished amount of hemoglobin. Without enough hemoglobin, red blood cells do not develop normally. The low number of mature red blood cells results to complications of anemia and other medical problems. Thalassemia major and thalassemia intermedia are inherited in autosomal-recessively, which means both copies of the gene in each cell have mutations. Most often, the parents of a person with an autosomal recessive condition each carry a copy of the mutated gene, but these typically do not show signs and symptoms of the condition. Sometimes, though, carriers of the altered HBB gene have a mild anemia referred to as thalassemia minor. In a small percentage of families, the HBB mutation is inherited autosomal-dominantly. In cases like these, one copy of the altered gene in each cell is sufficient to cause the disorder.
Beta Thalassemia Definition
Beta thalassemia is a hereditary blood disorder that reduces the production of hemoglobin. Hemoglobin is the substance in red blood cells that carries oxygen to cells throughout the body.
Beta Thalassemia Prevalence
All over the world, beta thalassemia is considered a fairly common blood disorder, affecting thousands of infants each year. Beta thalassemia occurs the most in Mediterranean countries, the Middle East, North Africa, India, Central Asia, and Southeast Asia.
Beta Thalassemia Symptoms and Signs
Symptoms of beta thalassemia take place when there is not enough oxygen that gets to various parts of the body due to low levels of hemoglobin and a shortage of red blood cells (or anemia). This disorder is categorized as thalassemia major (also known as Cooley's anemia) or thalassemia intermedia depending on how severe the symptoms are. Of the two types, thalassemia major is the more severe kind. Signs and symptoms of thalassemia major appear in the first 2 years of infancy. Babies have life-threatening anemia and become pale and tired. They also have a poor appetite, slow growth, and may develop jaundice, or the yellowing of the skin and whites of the eyes. The bones may be deformed and the liver, spleen and heart may be enlarged. Adolescents with thalassemia major may experience a delay in puberty. Signs and symptoms of thalassemia intermedia often appear in early childhood or later on in life. Individuals with thalassemia intermedia have mild to moderate anemia and may also have poor development and posses bone abnormalities.