Cause
Both α- and β-thalassemias are often inherited in an autosomal recessive manner. Cases of dominantly inherited α- and β-thalassemias have been reported, the first of which was in an Irish family with two deletions of 4 and 11 bp in exon 3 interrupted by an insertion of 5 bp in the β-globin gene. For the autosomal recessive forms of the disease, both parents must be carriers for a child to be affected. If both parents carry a hemoglobinopathy trait, the risk is 25% for each pregnancy for an affected child.The genes involved in thalassemia control the production of healthy hemoglobin. Hemoglobin binds oxygen in the lungs and releases it when the red cells reach peripheral tissues, such as the liver. The binding and release of oxygen by hemoglobin are essential for survival. Evolution
Having a single genetic variant for thalassemia may protect against malaria and thus can be an advantage.People diagnosed with heterozygous (carrier) β-thalassemia have some protection against coronary heart disease. Pathophysiology
Normally, the majority of adult hemoglobin (HbA) is composed of four protein chains, two α and two β-globin chains arranged into a heterotetramer. In thalassemia, patients have defects in either the α or β-globin chain, causing production of abnormal red blood cells.The thalassemias are classified according to which chain of the hemoglobin molecule is affected.
The most common of these are:

Hemoglobin E/thalassemia: common in Cambodia, Thailand, and parts of India, it is clinically similar to β thalassemia major or thalassemia intermedia. Hemoglobin S/thalassemia: common in African and Mediterranean populations, it is clinically similar to sickle-cell anemia, with the additional feature of splenomegaly. Hemoglobin C/thalassemia: common in Mediterranean and African populations, hemoglobin C/βo thalassemia causes a moderately severe hemolytic anemia with splenomegaly; hemoglobin C/β+ thalassemia produces a milder disease. Hemoglobin D/thalassemia: common in the northwestern parts of India and Pakistan (Punjab region). Diagnosis
Thalassemia can be diagnosed via a complete blood count, hemoglobin electrophoresis or high-performance liquid chromatography, and DNA testing. Hemoglobin electrophoresis is not widely available in developing countries, but the Mentzer index can also be used for diagnosis of thalassemia; it is not a definitive test but it can suggest the possibility of thalassemia. The Mentzer index can be calculated from a complete blood count report. Prevention
The American College of Obstetricians and Gynecologists recommends all people thinking of becoming pregnant be tested to see if they have thalassemia. Genetic counseling and genetic testing are recommended for families who carry a thalassemia trait.A screening policy exists in Cyprus to reduce the rate of thalassemia, which, since the programs implementation in the 1970s (also including prenatal screening and abortion), has reduced the number of children born with the disease from one of every 158 births to almost zero. Greece also has a screening program to identify people who are carriers.In Iran as a premarital screening, the mans red cell indices are checked first.