β-THALASSEMIA

Hemoglobinopathies are a group of diseases characterized by abnormalities in the synthesis of hemoglobin (Hb). They are genetically inherited disorders of hemoglobin structure or synthesis, typically transmitted via an autosomal recessive pattern. The clinical manifestations depend on the zygosity of the affected individual. 

Carrier State
The carrier or heterozygous state is characterized by the presence of one normal hemoglobin allele and one mutant allele. Individuals in this state generally remain clinically asymptomatic. Examples: sickle cell trait (HbAS), hemoglobin E trait (HbAE), etc.

Homozygous State
The homozygous state occurs when an individual inherits two identical mutant alleles, resulting in the absence of normal hemoglobin production or the presence of structurally defective hemoglobin. This genotype is associated with clinically significant disease manifestations, often severe in nature due to impaired oxygen transport and chronic hemolytic processes. Examples: sickle cell disease (HbSS), hemoglobin E disease (HbEE), etc.

β-thalassemia is one of the most prevalent hemoglobinopathies worldwide, characterized by reduced or no synthesis of the β-globin chains of hemoglobin. More than 200 β-gene mutations have been identified for β-thalassemia, occurring in a wide range of ethnic groups and geographic population.

β-thalassemia mutations are further divided into two broad categories, β⁰ (β-zero) thalassemia and β+ (β-plus) thalassemia. In β⁰ thalassemia, the affected β-globin gene produces no functional β-globin, usually due to a non-expressing mutation or less commonly, a gene deletion. In β+ thalassemia there is reduced expression of the abnormal gene so that even in the homozygous state there is still some hemoglobin A production.

β-thalassemia can be divided into three types:
1.    β-thalassemia trait
This state is characterized by heterozygosity of one deleted or mutated gene and one normal functioning gene and may therefore also be referred to as β-thalassemia minor. 
2.    β-thalassemia intermedia
These individuals will have a homozygous or heterozygous β-globin mutation that causes a decrease in β-chain production, but not to the degree that chronic transfusion therapy is necessary. 
3.    β-thalassemia major or Cooley’s anemia
β-thalassemia major refers to patients with homozygosity or compound heterozygosity for β-thalassemia who are dependent on blood transfusions to maintain life beyond early childhood.

The following test is used to screen and diagnose thalassemia condition and/or trait:

•   Quantification of hemoglobin A2 and F using Tosoh HLC-723G11