What Your Test Results Mean:

Carriers typically show no symptoms of beta thalassemia; however, carriers are at an increased risk of having a child with beta thalassemia or a hemoglobinopathy such as sickle cell beta thalassemia. Risk for the current or future pregnancies is dependent on your partner’s carrier status.

Disease Explained:

Beta thalassemia is an inherited disorder that affects red blood cells. The decrease in beta-globin leads to a relative excess of alpha-globin chains, causing the disease. Beta thalassemia major is a lifelong condition characterized by severe microcytic anemia, mild jaundice, bone deformities, and hepatosplenomegaly. Beta thalassemia minor is less severe and carriers of beta thalassemia are generally clinically normal.

Management of beta thalassemia major includes regular blood transfusions as well as chelation therapy to prevent iron overload. Without transfusion and proper treatment, beta thalassemia disease can be fatal within the first two years of life. Stem cell transplantation is curative; however, identifying matched donors has proven to be a barrier to transplantation.

How the Genetics Works:

The clinical features of beta thalassemia can be explained by pathogenic variants in the HBB gene. All individuals have two copies of the HBB gene. Carriers of beta thalassemia (beta thalassemia minor) have a variant in one copy of the HBB gene while individuals with beta thalassemia have variants in both copies the HBB gene, one inherited from each parent. The severity of the disease is dependent on the particular variants in the HBB gene. Individuals with one mild variant and one severe variant are classified as having beta thalassemia intermedia while individuals with two severe variants are classified as having beta thalassemia major.