Alpha-Thalassemia Carrier Screening

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Alpha-Thalassemia Carrier Screening

What Is Alpha-Thalassemia?

Alpha-thalassemia is an inherited blood disorder that causes anemia ("low blood") and other health problems. People with alpha-thalassemia have lower levels of something called hemoglobin. Hemoglobin is the protein in red blood cells that carries oxygen throughout the body.

Alpha-thalassemia is caused by changes, or mutations, in one or both of the two alpha-globin genes, called HBA1 and HBA2. These genes provide instructions on how to make hemoglobin. The most common mutations in HBA1 and HBA2 are deletions. Deletion means that a small piece of the gene is missing.

People with alpha-thalassemia can have anywhere from one to four mutations in HBA1 or HBA2. The number of mutations determines how severely alpha-thalassemia affects someone. People with one or two mutations are called carriers. Carriers usually don't have health problems, but may be at higher risk to have children affected with alpha-thalassemia. People with three or four mutations have alpha-thalassemia disease.

Below is a table outlining the differences between each alpha-thalassemia type:

Alpha-Thalassemia Type Number of mutations Symptoms
Alpha-+-Thalassemia ("silent carrier") 1 None
Alpha-0-Thalassemia ("alpha-thalassemia trait") 2 Mild anemia
Hemoglobin H Disease 3
  • Mild to moderate anemia
  • Pale skin, weakness, fatigue
  • Enlarged liver and/or spleen
  • Overgrowth of upper jaw and prominent forehead
  • Symptoms usually develop in late childhood or early adulthood
  • Can be treated with blood transfusions
Alpha-thalassemia major (Hemoglobin Bart Syndrome) 4
  • Severe anemia
  • Excessive fluid build-up in the developing baby (hydrops fetalis)
  • In developing countries, babies with alpha-thalassemia major are either stillborn or die shortly after birth. In the US, most are found to have hydrops fetalis via prenatal ultrasound.
  • Enlarged liver and spleen
  • Increased chance for pregnancy complications for the mother (preeclampsia, premature delivery, and abnormal bleeding)
  • No effective treatment

Next: Who Is At Risk for Alpha-Thalassemia?