Alpha-thalassemia

Alpha-thalassemia (α-thalassemia, α-thalassaemia) is an inherited blood disorder and a form of thalassemia. Thalassemias are a group of inherited blood conditions which result in the impaired production of hemoglobin, the molecule that carries oxygen in the blood. Symptoms depend on the extent to which hemoglobin is deficient, and include anemia, pallor, tiredness, enlargement of the spleen, iron overload, abnormal bone structure, jaundice, and gallstones. In severe cases death ensues, often in infancy, or death of the unborn fetus. The disease is characterised by reduced production of the alpha-globin component of hemoglobin, caused by inherited mutations affecting the genes HBA1 and HBA2. This causes reduced levels of hemoglobin leading to anemia, while the accumulation of surplus beta-globin, the other structural component of hemoglobin, damages red blood cells and shortens their life. Diagnosis is by checking the medical history of near relatives, microscopic examination of blood smear, ferritin test, hemoglobin electrophoresis, and DNA sequencing. As an inherited condition, alpha thalassemia cannot be prevented although genetic counselling of parents prior to conception can propose the use of donor sperm or eggs. The principle form of management is blood transfusion every 3 to 4 weeks, which relieves the anemia but leads to iron overload and possible immune reaction. Medication includes folate supplementation, iron chelation, bisphosphonates, and removal of the spleen. Alpha thalassemia can also be treated by bone marrow transplant from a well matched donor. Thalassemias were first identified in severely sick children in 1925, with identification of alpha and beta subtypes in 1965. Alpha thalassemia has its greatest prevalence in populations originating from Southeast Asia, Mediterranean countries, Africa, the Middle East, India, and Central Asia. Having a mild form of alpha thalassemia has been demonstrated to protect against malaria and thus can be an advantage in malaria endemic areas.