How can sickle cell be beneficial

The cause of sickle cell anemia was attributed unequivocally to a single base substitution in the DNA sequence of the gene encoding the beta chain of hemoglobin, the protein that carries oxygen in red blood cells. Only those individual that inherit two copies of the sickle mutation one from their mother and the other from their father develop sickle cell anemia. If untreated, these individuals have a shorter than normal life expectancy and as such it would be expected that this mutation would be rare in human populations.

This is however, far from being the case. Individuals carrying just one copy of the sickle mutation inherited from either the father or mother were known not to develop sickle cell anemia, leading rather normal lives. However, it was found that these same individuals, said to carry the sickle cell trait, were in fact highly protected against malaria, thus explaining the high prevalence of this mutation in geographical areas where malaria is endemic.

These findings lead to the widespread believe in the medical community that understanding the mechanism whereby sickle cell trait protects against malaria would provide critical insight into developing treatment or a possible cure for this devastating disease, responsible for over a million premature deaths in sub-Saharan Africa. Despite several decades of research, the mechanism underlying this protective effect remained elusive.

Until now. Several studies suggested that, in one way or another, sickle hemoglobin might get in the way of the Plasmodium parasite infecting red blood cells, reducing the number of parasites that actually infect the host and thus conferring some protection against the disease. Subscribe to our newsletter.

Email Facebook Twitter. She does not have the disease, but the gene that she carries still affects her, her cells, and her proteins: There are effects at the DNA level There are effects at the protein level Normal hemoglobin left and hemoglobin in sickled red blood cells right look different; the mutation in the DNA slightly changes the shape of the hemoglobin molecule, allowing it to clump together.

Normal red blood cells top and sickle cells bottom. Previous The effects of mutations. Next Mutations are random. The rapid breakdown of red blood cells may also cause yellowing of the eyes and skin, which are signs of jaundice. Painful episodes can occur when sickled red blood cells, which are stiff and inflexible, get stuck in small blood vessels. These episodes deprive tissues and organs, such as the lungs, kidneys, spleen, and brain, of oxygen-rich blood and can lead to organ damage.

A particularly serious complication of sickle cell disease is high blood pressure in the blood vessels that supply the lungs pulmonary hypertension , which can lead to heart failure. Pulmonary hypertension occurs in about 10 percent of adults with sickle cell disease. Sickle cell disease affects millions of people worldwide.

Sickle cell disease is the most common inherited blood disorder in the United States, affecting an estimated , Americans. The disease is estimated to occur in 1 in African Americans and 1 in 1, to 1, Hispanic Americans.

Mutations in the HBB gene cause sickle cell disease. The HBB gene provides instructions for making one part of hemoglobin. Hemoglobin consists of four protein subunits, typically, two subunits called alpha-globin and two subunits called beta-globin. The HBB gene provides instructions for making beta-globin. Various versions of beta-globin result from different mutations in the HBB gene. HBB gene mutations can also result in an unusually low level of beta-globin; this abnormality is called beta thalassemia.

In people with sickle cell disease, at least one of the beta-globin subunits in hemoglobin is replaced with hemoglobin S. People with sickle cell disease often have a low number of red blood cells, or anemia. Signs of anemia include:. People with sickle cell anemia may have jaundice skin and whites of the eyes look yellow. This happens because the sickle-shaped red blood cells break down faster than normal cells.

People with sickle cell disease are also at risk for problems such as leg ulcers, bone or joint damage, gallstones, kidney damage, eye damage, and delayed growth. Sickle cell disease is not contagious, so you can't catch it from someone else or pass it to another person like a cold or an infection. People with sickle cell disease have it because they inherited two sickle cell genes , one from each parent.

In some types of sickle cell disease, people can inherit a sickle cell gene from one parent and a different abnormal hemoglobin gene from the other parent. A person who inherits the sickle cell gene from only one parent will not develop the disease, but will have something called sickle cell trait. People with sickle cell trait often don't have any signs of the disease, but they can pass the sickle cell gene to their children.

Stem cell transplant also called bone marrow transplant is the only known cure for sickle cell disease. Transplants are complex and risky procedures, and for now are an option only for some patients.

Scientists are studying gene therapy as a treatment for sickle cell anemia. One day, it's hoped that doctors can stop the disease by changing or replacing the abnormal gene that causes it.