This refers to a condition in which a person has inherited two genes for hemoglobin S, one from each parent. This is the most common of the sickle syndromes. The condition formerly was referred to as sickle cell anemia. This term has been largely replaced in standard usage, since it emphasizes the anemia, which is the least important manifestation of this potentially devastating condition. The severity of sickle cell disease varies tremendously.
Some patients have almost no symptoms, while others are virtually incapacitated.
Although we have some clues as to the cause of the variable expression of the disorder, most of the heterogeneity is unexplained. The hemoglobin of these patients can be analyzed by a special laboratory technique, called hemoglobin electrophoresis. These patients have primarily hemoglobin S in their red blood cells, with small amounts of two other hemoglobins in some cases. Most importantly, these patients have no normal hemoglobin. In this condition, the patient has inherited a gene for hemoglobin S from one parent and a gene for beta-thalassemia from the other.