Thalassemia is the name of a group of genetic blood disorders. To understand how thalassemia affects the human body, you must first understand a little about how blood is made.

Hemoglobin is the oxygen-carrying component of the red blood cells. It consists of two different proteins, an alpha and a beta. If the body doesn't produce enough of either of these two proteins, the red blood cells do not form properly and cannot carry sufficient oxygen. The result is anemia that begins in early childhood and lasts throughout life.

Since thalassemia is not a single disorder but a group of related disorders that affect the human body in similar ways, it is important to understand the differences between the various types of thalassemia.

Alpha Thalassemia - Beta Thalassemia - Variant Hemoglobin

Unfortunately, Thalassemia is a lot more common than most people think, especially in parts of South East Asia including Thailand. Up to 40% of Thais will be a carrier of a Thalassemia trait or of HbE. Carrier rates are also high in people from some other ethnic groups, for example the Mediterranean, while the carrier rate is much lower in other ethnic groups. For example a Thalassemia gene is found in only 1 in 1000 people from Northern Europe. Just over 1% of Thai couples will have a child affected by Thalassemia

If you have a family history of Thalassemia, the chance that you are a carrier will be higher. However, some children born with thalassemia do not have a family history of the disease.

When two carriers of beta thalassemia have a child, there is a 1 in 4 chance (25%) their child will have thalassemia, a 1 in 2 chance (50%) that their child will be a carrier like them, and a 1 in 4 chance the child will have normal genes. See diagram.

It follows that just because a couple has had one or more non-thalassemia children. It does not mean that they are not carriers of a thalassemia gene and that future children will not be affected.

Thalassemia may be curable by stem cell or bone marrow transplantation, but it is preventable by screening and PGD
The key to preventing thalassemia lies in genetic screening and the first step is quick and simple. From a blood sample, scientists can determine if you are a thalassemia carrier.

For any untested Thai couple without a family history of thalassemia, the risk of carrying a thalassemia gene error is about 40% for each person or about 16% for both of the couple. The chance of having an affected child is about 1 in 100. Screening can help to more accurately assess your risk. We think it is important for you to have the option for testing if you are considering a pregnancy.

If a thalassemia mutation is identified, your doctor will discuss with you the risk of having a baby with thalassemia, and may arrange for you to have genetic counseling. Because the thalassemia gene is inherited, your blood relatives will have a high chance of also carrying the gene error. Your relatives may also want to have thalassemia screening.

In the case where both parents test positive as thalassemia carriers, there are several options. Couples can have a baby naturally and take the risk of having an affected child, couples can have prenatal testing at around 12-14 weeks of pregnancy and choose to terminate the pregnancy if foetus is affected, or couples can have PGD, preimplantation genetic diagnosis, and transfer an embryo not affected by thalassemia.
It is now possible to undergo PGD for human leukocyte antigen (HLA) matching to you for the purpose of having a HLA-matched hematopoietic progenitor cell (HPC) donor for your Thalassemia affected child.. The PGD procedure allows genetic testing to be performed on early embryos before implantation and pregnancy development for the purpose of selecting only those embryos that are HLA matched to your affected child.

When a couple has a child with a single gene disorder like Thalassemia that requires an HPC transplant, the optimal source of cells needed for transplant is an HLA-matched sibling. Donors cells need to be HLA-matched to an affected child avoid any chance for the transplanted cells to react against the child’s body. If you undertake a natural pregnancy in the hope of having a child who is an HLA match to your affected child, there is 1 in 5 chance of conceiving a child who is an HLA match to the affected biological child.

Following IVF, Preimplantation genetic diagnosis can be used for selecting and transferring only the embryos that are HLA matched to your affected child. Each embryo has a 1 in 5 chance of matching the affected biological child. With PGD, the goal is to select those embryos that are a match and transfer them. In this process, we can significantly increase the chance to have a child that is HLA-matched to your affected child.