When a patient has a type of thalassemia, the unaffected globin chains are produced at the normal rate; however, there are insufficient numbers of the affected globin chains produced to pair with the normal ones. Therefore, these normal globin chains accumulate within the red blood cell.
In the alpha thalassemia disorders, this excess accumulation of normal chains can have the following outcomes: In infants, who produce hemoglobin F (two alpha, two gamma), those excess normal gamma chains will actually pair up with each other since they don’t have the alpha chains to pair up with. This four-gamma hemoglobin tetramer is known as hemoglobin Bart’s. In adults who produce mainly Hb A (two alpha, two beta), the normal beta chains pair with each other to produce what is known as hemoglobin H (4 betas). These abnormal tetramers can precipitate out, leading to destruction of the RBC in the spleen and a hemolytic anemia.
