September is National Sickle Cell Awareness Month, so what better time is there to report on positive developments in the treatment of sickle cell disease (SCD)?
A short primer on SCD
Sickle cell disease (SCD) is a genetic blood disorder that’s inherited—it’s passed from parents to children. Babies are born with sickle cell disease when they inherit two abnormal genes, one from each parent. A baby who inherits one abnormal gene from one parent is a carrier because of having the sickle cell trait but not the actual disease. If that baby grows up to marry another carrier, then their baby might have the actual disease.
These genes cause the body’s red blood cells to become misshaped, changing them from disk-shaped to a curved shape that look like a crescent moon or an old farm tool known as a sickle. These “sickle” cells tend to stick together and block the flow of blood and oxygen to the body, causing pain in the extremities and back, infections, organ failure and other tissue damage, skin infections, loss of eyesight, severe blood clots and strokes. These complications tend to progress at adolescence and worsen during early adulthood with eventual early mortality.
What is the difference between sickle cell disease and sickle cell anemia?
There are several types of sickle cell disease, and the most common is sickle cell anemia. With sickle cell disease, the blood cells don’t last as long as they do in healthy people (10–20 days as opposed to 120 days). The bone marrow can’t replace these blood cells fast enough, which causes anemia. People with SCD will usually have anemia.
Who is affected by SCD?
Sickle cell disease (SCD) is particularly common among those whose ancestors came from sub-Saharan Africa; Spanish-speaking regions in the Western Hemisphere (South America, the Caribbean, and Central America); Saudi Arabia; India; and Mediterranean countries such as Turkey, Greece, and Italy.
How common is SCD?
SCD is considered rare, affecting approximately 100,000 Americans. It is, however, more common among African American and Hispanic Americans:
- SCD occurs among about one out of every 365 Black or African-American births.
- SCD occurs among about one out of every 16,300 Hispanic-American births.
- About one in 13 Black or African-American babies is born with sickle cell trait (SCT).
Promise for treating the disease in children
A recently completed large-scale analysis shows that stem cell transplants are successful in most children with sibling donors. The study looked at the results of 1000 patients, with an average age of nine years old, who received stem cell transplants from a matched sibling. The three year overall survival rate was 99 percent for patients who received donor cord blood, 94 percent for those who received donor bone marrow and 80 percent for those who received transplanted peripheral blood.
Read more about cord blood's advantages over bone marrow.
This study strengthens several earlier studies, attesting to the excellent outcomes of cord blood transplants to treat sickle cell disease. An earlier National Institute of Health (NIH) study showed that the possibility of treatment for adults suffering from sickle cell anemia has greatly improved. Matched-sibling donors showed a high success rate for a stem cell transplant therapy. The National Institute of Health's Dr. Matthew Hsieh and his team disproved the hypothesis that adults are too likely to reject the stem cell transplant becasue of toxicity. The creative and effective therapy used in the study solved this obstacle with impressive success.
A separate UCLA study led by Dr. Donald Kohn of UCLA’s Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research examined treating sickle cell anemia with blood stem cells from a patient's own blood; a method previously thought impossible. This gene therapy approach is a revolutionary alternative to current sickle cell disease treatments. Since it uses the patient’s own blood, it does not rely on the identification of a matched donor, thus completely avoiding the risk of rejection of donor stem cells. The possibility of these new stem cell treatments would allow doctors to have an exponentially greater chance of finding a match for patients, young and old, that suffer from this common inherited blood disorder.
First published in July 2014. Revised and republished in September 2016.