ALPHA-THALASSEMIA: WHAT IS ALPHA-THALASSEMIA?
Definition: What is "Alpha-thalassemia"?
Alpha-thalassemia definition: In this condition, "a thalassemias" involve genes HBA1 & HBA2, which occurs due to Mendelian inheritance in a recessive fashion. Alpha-thalassemia is also connected to the deletion of 16p chromosome. Alpha-thalassemia results in a decrease in alpha-globin production that causes a decrease in the production of alpha-globin chains. As a result, an excess of beta chains occur in adults, while an excess of gamma chains occur in newborns.
There are four genetic loci for "a blobin" - 2 are maternal in origin, while the other 2 are paternal in origin. The severity of this condition depends on the number of affected "a globin loci". As such, the greater the number of affected loci, the more serious will the manifestations of the disease be. 1) If only one "a loci" is affected, symptoms are rare & there is minimal effect. Three normal a-globin loci are enough for hemoglobin production. As such, those with this type of condition will not develop anemia or hypochromia. Because of this, patients with this condition are called "silent carriers". 2) Alpha thalassemia is called when two "a loci" are affected. A mild microcytic hypochromic anemia occurs. However, it is usually mistaken for iron deficiency anemia, so it is treated wrongly with iron. 3) Hemoglobin H disease is called when three loci are affected. Since two unstable hemoglobins - Hemoglobin Bart & Hemoglobin H - are present in the blood, it results in poor oxygen delivery to tissues. Patients experience microcytic hypochromic anemia & splenomegaly. This condition may be noticed initially in childhood. 4) If all 4 loci are affected, no fetus can survive outside the uterus. Unfortunately, newborns with this condition die shortly after birth because only a few hemoglobins are circulating.
Thalassemia is an inherited "autosomal recessive blood disease". The genetic defect in this condition results in a reduced rate of synthesis on one of the "globin chains" that comprises hemoglobin, which causes the formation of abnormal hemoglobin molecules. Because of these abnormal formations, patients with alpha-thalassemia will develop anemia - the primary symptom of the disease.