Which Thalassemia Is Most Common?

Thalassemia is a blood disorder characterized by abnormal production of hemoglobin. This form of blood disorder is classified under the quantitative hemoglobin chain disorders. The disease was limited to tropical and subtropical region, but the disease is now spread across the globe due to migration of people.^[1] Thalassemia is broadly classified into two types based on the affected globin chain, i.e. Alpha or beta globin chain. The name alpha thalassemia or beta thalassemia indicates the type of globin chain affected.^[2]

Alpha thalassemia is the most common form of thalassemia. Alpha thalassemia is an autosomal recessive disorder and the incidences of alpha thalassemia have increased in United States and other Western nations because of migration. The region’s most commonly affected with Alpha-thalassemia are Southeast Asian descent, Sub-Saharan Africa and Western Pacific regions.^[3]

HbH disease and Hb Bart’s hydrops fetalis are the severe forms of Alpha thalassemia. The prevalence of this disease is approximately 1 in 1,000,000 individuals in the Northern Europe and North American region. Certain studies indicate that alpha thalassemia is underdiagnosed and hence the frequency of the affected population is not accurately determined.^[4]

According to some studies 5% of the world’s population carries an alpha-thalassemia mutation in one or two pairs of genes of alpha thalassemia.^[5] Alpha thalassemia is the most common form of thalassemia across the globe with special prevalence in Middle East, Southeast Asia, and Mediterranean countries.

Beta Thalassemia

The regions that are most commonly affected with Beta-thalassemia are Mediterranean, African and South Asian ancestry. Beta thalassemia is rare in United States, but the risk of Beta thalassemia is increasing because of migration of people from the affected region.^[6]

Pattern Of Inheritance

Thalassemia traits are similar to any other genetic traits as passed form the parents to their offspring. The type of thalassemia which the child may have or have depends upon the type of trait inherited by the offspring. In case both the parents’ have beta thalassemia trait, and then the offspring will have beta thalassemia major. If one of the parents have alpha thalassemia trait and the other parent has normal traits then the offspring is likely to receive alpha thalassemia trait. Traits are passed from generation to generation and the offspring are at risk of developing thalassemia. Traits do not produce any symptoms of the disease.

The severity of alpha and beta thalassemia depends on how many of the alpha globin or beta globin chains are missing. The carriers of Thalassemia can be detected by routine hematological methods. The person who has Thalassemia has structural variation in the hemoglobin of their red cells. The carriers of Thalassemia have relatively small red blood cells and suffer from mild anemia.

This is often misdiagnosed as iron deficiency anemia. The diagnosis of Thalassemia has to be differentiated from anemia as the two blood disorders looks similar and needs differential diagnosis. The patients who are the carriers of β thalassemia have more than 3.5% of Hb A2.^[7] The terms “trait,” “minor,” “intermedia” or “major” are used to express the severity of thalassemia. A person who is expressing only a thalassemia trait will not have any symptoms and probably have only mild form of anemia.

On the other hand patients suffering from thalassemia major have severe symptoms of the disease and the patients will be undergoing frequent blood transfusion to increase the life expectancy and also to improve quality of life.^[8] Such patients will have iron overload in the body requiring the need of iron chelators. Doctors prescribe medicines to decrease the iron deposition in the vital organs such as liver and kidney.

Conclusion

Beta thalassemia is a comparatively rare blood disorder in the United States, but Alpha thalassemia is one of the most common autosomal recessive disorders in the world. The occurrence of Beta thalassemia is estimated to be approximately 1 in 100,000 individuals. Thousands of infants are born every year in Mediterranean countries, Middle East, Southeast Asia, Central Asia and North Africa with beta thalassemia.

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Which Thalassemia Is Most Common?