The several types of thalassemia may be divided into two groups: Alpha and Beta
People with alphathalassemia have one or more mutations in the chromosome 16 – genetic defect which affects production of the two chains α (alpha) of globin that, jointly with the two chains beta, comprise the hemoglobin. This condition may provoke both decrease of the chains alpha and their total scarcity.
The individual may only inherit the problem from one of the parents and become a bearer of the defective gene or genes which lead to alphathalassemia, without presenting the anemia symptoms or requiring treatment. In some people with thalassemia, in whom the genetic mutation is light and affects quality of only a small amount of hemoglobins, one can observe a minor anemia, which usually only concerns and deserves medical monitoring in specific situations, which are usually aggravated such as surgeries, pregnancy and in the senior age.
Another possibility is that the person with thalassemia develops the so-called hemoglobin disease H (HbH), when decrease of the alpha chains is aggravated. Since the beta chains continue to be produced, the remainders start to be connected between themselves, originating a new type of hemoglobin, the H (HbH). Such molecule has the same function of a normal adult hemoglobin, which is oxygenating the cells, tissues and organs. The fact is that, since it is more unstable, the average life of the HbH is lower, and the status will soon develop to anemia, from moderate to severe, with all consequences for the organism – such as fatigue, bone deformation and increase of the liver – if it is not treated. (See details on these complications in the link on MAJOR thalassemia). For the patients with the hemoglobin H disease, the recommendation is the periodical treatment with blood transfusion, in a specialized center, in addition to medical monitoring and general check-up on an annual basis.
On the other hand, when the mutations in the chromosome 16 lead to full incapacity of the organism to produce the alpha chains, the production of normal hemoglobin – which is comprised of two alpha globin chains and two of beta – does not occur as well. The status, known as fetal hydropsy, is rare and, since it does not have the presence of the molecule responsible for taking oxygen to the cells, tissues and organs, causes death of the baby in formation yet in the uterus.
The beta-thalassemias are the most frequent in Brazil and around the world, and people with this type of thalassemia have one or more mutations in the chromosome 11. The genetic defect affects production of the two β (beta) chains, which, jointly with the two alpha chains, form the hemoglobin. This condition may cause decrease of the beta chains and its full scarcity in the organism. There is a variety of subtypes of beta-thalassemia, caused by about one thousand mutations already described in the medicine, but they are usually classified in three basic forms: minor (or thalassemic trace), intermediate and major thalassemia.