Beta-thalassemia major and beta-thalassemia intermedia are usually inherited in an autosomal recessive manner, which means both copies of the HBB gene in each cell have mutations. The parents of a person with an autosomal recessive condition each carry one copy of the mutated gene and are referred to as carriers. When two carriers have children, each child has a 25% (1 in 4) chance to be affected, a 50% (1 in 2) chance to be a carrier like each parent, and a 25% (1 in 4) chance to be unaffected and not be a carrier. Sometimes, people with only one HBB gene mutation in each cell (carriers) do have mild anemia. These people are said to have 'beta-thalassemia minor' or 'beta-thalassemia trait.'
In a small percentage of families, the condition is inherited in an autosomal dominant manner. In these cases, one mutated copy of the gene in each cell is enough to cause the signs and symptoms of beta-thalassemia.
Last updated: 7/29/2015
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