This is the fifth part of our series about the condition based on our patient booklet “Fast Facts for Patients: Alpha Thalassemia”. This article explains four gene changes in alpha thalassemia (AT).

If you have four gene changes, you have no genes that make alpha chains properly. This is called AT major or Hb Barts disease. This is the most serious form of AT.

What Does This Mean?

When a baby starts to develop in the womb, the first type of Hb its body makes is called embryonic Hb, which doesn’t include any alpha chains. By 16 weeks, the baby begins to make another type of Hb called fetal Hb, which needs alpha chains.

A baby with four gene changes can’t make alpha chains, so fetal Hb cannot develop. Instead, a type of Hb called Hb Barts is made. The baby will develop severe anemia and will die in the womb without treatment. Doctors call this ‘hydrops fetalis’ (or just ‘hydrops’ for short).

Fetal Hb is made up of alpha and gamma Hb chains

 

It may be possible for the baby to have red blood cell transfusions while still inside the womb (this is called intrauterine transfusion), so the chance of the baby living until birth is greatly increased. However, there is still a high risk of premature birth.

Your health will also be closely monitored throughout your pregnancy. Your medical team will do everything they can to lower the risk of complications for both you and the baby.

What Is the Risk If I Have Children?

If one parent has four gene changes and their partner has two gene changes on the same chromosome, for each pregnancy there is a:

  • 1 in 2 chance (50%) the baby will have AT major (four gene changes)
  • 1 in 2 chance (50%) the baby will have AT trait (two AT genes on the same chromosome).

 

One parent has four gene changes and their partner has two gene changes on the same chromosome

 

If one parent has four gene changes and their partner has two gene changes on different chromosomes, every child will have HbH AT (three gene changes).

 

One parent has four gene changes and their partner has two gene changes on different chromosomes

 

If one parent has four gene changes and their partner has HbH AT (three gene changes), for each pregnancy there is a:

  • 1 in 2 chance (50%) the baby will have AT major (four gene changes)
  • 1 in 2 chance (50%) the baby will have HbH AT (three gene changes).

 

One parent has four gene changes and their partner has HbH AT (three gene changes)

 

Please check out the other posts of our series here:

 

Information based on Fast Facts for Patients: Alpha Thalassemia (Karger, 2023).

Related Posts

Platelets, a type of blood cell, are involved in the control of blood loss. In the review article “In vitro...
Immunohematology is the study of antigens on red blood cells and antibodies that are associated with blood transfusions. In the...
Primary immune thrombocytopenia is a type of autoimmune disorder. In the research article “The Role of Follicular Regulatory T Cells/Follicular...

Comments

Share your opinion with us and leave a comment below!