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

If you have two gene changes, you are said to have AT trait, which is also called AT minor.

What Does This Mean?

Most people with two gene changes don’t have any serious health problems related to AT, apart from mild anemia (a shortage of healthy red blood cells). Anemia can cause fatigue, particularly after exercise).

Under a microscope, your red blood cells will look smaller than usual. Doctors call small red blood cells microcytosis. The cells look like this because of a lack of Hb.

Important: If you’re anemic, make sure your doctor knows that you have AT trait (or that there is thalassemia in your family if you haven’t been tested). If the doctor doesn’t know this, they may prescribe an iron supplement for your anemia but that’s something you definitely don’t need if you have AT because you may develop ‘iron overload’. Iron overload is harmful.

Microcytosis is the term used to describe red blood cells that are unusually small.

 

Normal red blood cells and microcytic red blood cells

 

When one parent has two gene changes on the same chromosome and the other parent has no gene changes, for each pregnancy there is a:

  • 1 in 2 chance (50%) the baby will have AT trait (two gene changes)
  • 1 in 2 chance (50%) the baby won’t have any gene changes.

 

Alpha thalassemia: one parent with two gene changes on the same chromosome and the other parent with no gene changes

 

If both parents have two gene changes on the same chromosome, for each pregnancy there is a:

  • 1 in 4 chance (25%) the baby will have AT major (four gene changes)
  • 1 in 2 chance (50%) the baby will have AT trait with two gene changes on the same chromosome
  • 1 in 4 chance (25%) the baby won’t have any gene changes.

 

Alpha thalassemia: both parents with two gene changes on the same chromosome

 

If one parent has gene changes on each chromosome but the other parent has no gene changes, every child will be a carrier.

 

Alpha thalassemia: one parent with gene changes on each chromosome but the other parent without gene changes

 

If both parents have gene changes on each chromosome, every child will have AT trait.

 

Alpha thalassemia: both parents with gene changes on each chromosome

 

Please check out the other posts of our series here:

 

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

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