Do Factors Other Than The Sickle Genes Influence Sickle Cell Disease?
Sickle cell disease is quite variable in itself. We know of only a few of the factors that contribute to this variability. Some are genetic. Others likely involve environmental influences. One of the most important genetic factors is thalassemia. One form of thalassemia, called b-thalassemia, reduces the production of normal hemoglobin. A person with one normal hemoglobin gene and one thalassemia gene has thalassemia trait (also called thalassemia minor). Should one parent have sickle cell trait and the other have thalassemia trait, any child they conceive has one chance in four of receiving one gene for sickle cell disease and one gene for b-thalassemia (Figure 2). This condition is called sickle b-thalassemia. The severity varies. Some patients with sickle b-thalassemia have a condition as severe as sickle cell disease itself. Others have few and relatively mild problems. The gene for thalassemia is very common among people of Mediterranean origin. The sickle gene also exists in peop
