Beta thalassemia is a blood disorder that reduces the production of hemoglobin, which is the iron-containing protein having two alpha and two beta chains, it carries oxygen to cells throughout the body. Beta thalassemia is classified into two types depending on the severity of symptoms: thalassemia major and thalassemia intermedia. Of the two types, thalassemia major is more severe.
In Pakistan the frequency of beta thalassemia carrier is about 5%. Thousands of infants with beta thalassemia are born each year. Beta thalassemia most frequently occurs in people from Mediterranean countries, North Africa, the Middle East, India, Central Asia, and Southeast Asia.
Genetic mutation associated with Beta Thalassemia
Beta thalassemia is caused due to mutations in the HBB gene. This gene provides instructions for making a protein called beta-globin. Beta-globin is a subunit of hemoglobin. Hemoglobin consists of four protein subunits, typically two subunits of beta-globin and two subunits of another protein called alpha-globin. Patient having one affected allele are called trait or carrier while patient with both affected allele are called as Beta thalassemia Major.
Most common mutation in Pakistan are Fr8-9 (+G) and IVS1-5 (G-C). However other beta mutation which occur in low frequency are Fr 4142 (-TCTT), Cd15 (G-A), Cd5 (-CT), IVS 1-1 (G-T), IVS1-1 (G-A), Cd30 (G-C), Cd30 (G-A), Fr16 (-C), IVSII-I (G-A), Del 619, Cap+ 1).
Beta-thalassemia (β-thalassemia) is characterized by reduced synthesis of the hemoglobin subunit beta (hemoglobin beta chain) that results in microcytic hypochromic anemia, an abnormal peripheral blood smear with nucleated red blood cells, and reduced amounts of hemoglobin A (HbA) on hemoglobin analysis.
However for the identification of specific mutation associated with Beta thalassemia in a particular patient, genetic profile for beta thalassemia is recommended, which is either carried out through PCR, or sequencing of the HBB gene.
Prenatal diagnosis is recommended in carrier couples who wish to have healthy children; it is generally performed between 12-15 weeks of pregnancy.