Each person inherits genes that make hemoglobin from both of their parents.
Some individuals inherit abnormal genes that can cause hemoglobin disorders.
In diseases called thalassemias , the hemoglobin genes make normal hemoglobin but not enough to supply the body with sufficient oxygen. Inheriting one or more thalassemia genes from one or both parents can cause mild to severe anemia. In diseases called hemoglobinopathies , the hemoglobin genes make abnormal hemoglobins that may not function like normal hemoglobin. Unlike the thalassemias, usually two abnormal genes must be inherited to cause disease. The best known example is Sickle Cell Disease, a serious hemoglobinopathy that causes anemia, susceptibility to infection, and organ damage in infants who inherit a gene for sickle hemoglobin from each parent.