Treatment Options and Continuing Research

Therapy for sickle cell disease used to focus on easing symptoms and treating infections, which are the most common cause of death in children who have this disease. Newer therapies actually treat the disease.

Hydroxyurea and erythropoietin, for example, are two medications that stimulate the bone marrow to produce more fetal hemoglobin, HbF. Production of both red blood cells and hemoglobin occurs in this spongy tissue, which is located in certain bones.

Fetal hemoglobin can transport oxygen but does not polymerize, so the red blood cells cannot sickle. Thus these drugs can prevent vaso-occlusive crises. However, they do have side effects that can limit their usefulness. Hydroxyurea, for example, can suppress bone marrow function.

Normally, the production of HbF is turned off shortly after birth. Scientists are trying to determine how to reactivate the gene for HbF so that the bone marrow of people with sickle cell disease can continually produce fetal hemoglobin without the use of medications. Other research focuses on learning how to insert normal beta chains and regulatory genes into stem cells, which are cells that develop into erythrocytes.

Bone marrow transplants are a new treatment and have largely been conducted in Europe. The donor bone marrow will produce normal hemoglobin and normal red blood cells. However, the tissue must come from an immunologically compatible donor. Also, a bone marrow transplant is a complicated process, and some people have died during the procedure.

A ribbon diagram of hemoglobin. The four ball-and-stick structures are the heme groups. The helices and loops are the two alpha and two beta globin chains. Adapted from <http://www.ee .seikei.ac.jp/user/seiichi/ lecture/Biomedical/02/ graphics/hemoglobin.gif>.

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