Sickle Cell Anemia: When a child inherits two substitution beta globin genes (the sickle cell gene) from both parents, the child has Sickle Cell Anemia (SS). Individuals with sickle cell anemia may acquire symptoms of sickle cell disease. Populations that have a high frequency of sickle cell anemia are those of African and Indian descents.
Sickle-Hemoglobin C Disease: Individuals with Sickle-Hemoglobin C Disease (SC) have a slightly different substitution in their beta globin genes that produces both hemoglobin C and hemoglobin S. Sickle-Hemoglobin C disease may cause similar symptoms as sickle cell anemia but less anemia due to a higher blood count level. Populations that have a high frequency of Sickle-Hemoglobin C disease are those of West African, Mediterranean and Middle Eastern descents.
Sickle Beta Thalassemia Disease: Individuals with Sickle Beta Thalassemia (Sb) disease also contain substitutions in both beta globin genes. The severity of the disease varies according to the amount of normal beta globin produced. When no beta globin is produced, the symptoms are almost identical to sickle cell anemia, with severe cases needing chronic blood transfusions. Populations that have a high frequency of Sickle Beta Thalassemia are those of Mediterranean and Caribbean descents.
Sickle-Hemoglobin D Disease: Through research, hemoglobin D, which is a different substitution of the beta globin gene, has been found to interact with the sickle hemoglobin gene. Individuals with Sickle-Hemoglobin D disease (SD) have moderately severe anemia and occasional pain episodes. Populations that have a high frequency of Sickle-Hemoglobin D disease are those of Asian and Latin American descents.
Sickle-Hemoglobin O Disease: Hemoglobin O, another type of substitution in the beta globin gene, also interacts with sickle hemoglobin. Individuals with Sickle-Hemoglobin O disease (SO) can have symptoms of sickle cell anemia. Populations that have a high frequency of Sickle-Hemoglobin O disease are those of Arabian, North African and Eastern Mediterranean descents.
Sickle cell trait (AS) is not a “type” of sickle cell disease. It is an inherited condition in which both hemoglobin A and S are produced in the red blood cells, always more A than S. Individuals with sickle cell trait are generally healthy.
Sickle cell conditions are inherited from parents in much the same way as blood type, hair color and texture, eye color and other physical traits. The types of hemoglobin a person makes in the red blood cells depend upon what hemoglobin genes the person inherits from both parents. Like most genes, hemoglobin genes are inherited in two sets: one from each parent.
- Examples: If one parent has sickle cell anemia (SS) and the other has normal (AA) blood, all of the children will have sickle cell trait. If one parent has sickle cell anemia (SS) and the other has sickle cell trait (AS), there is a 50% chance (1 chance out of 2) of having a baby with either sickle cell disease or sickle cell trait with each pregnancy. When both parents have sickle cell trait (AS), they have a 25% chance (1 chance out of 4) of having a baby with sickle cell disease with each pregnancy.
A simple painless blood test followed by a laboratory technique called Hemoglobin Electrophoresis will determine the type of hemoglobin. When an electric charge is passed through a solution of hemoglobin, distinct hemoglobins move different distances, depending on their composition. This technique differentiates between normal hemoglobin (A), sickle hemoglobin (S), and other different kinds of hemoglobin (such as C, D, E, etc.).