Sickle Cell Anemia
By: Neerja Bathla (Paradise High School)
What is Sickle Cell ?
Sickle Cell Anemia is an inherited blood disorder when a point mutation causes a single amino acid in thousands to be out of order in the genetic code for hemoglobin. Hemoglobin is the protein in red blood cells that carries oxygen. Sickle cell anemia interferes with oxygen delivery to the tissues. Normal red blood cells are round and flexible. In sickle cell anemia, the red blood cell is in a sickle shape and pointy at both edges. While the normal red blood cell squeezes through the veins, the sickle cell cannot do that and it can get clogged in and hurt going through the veins. This happens when sickle cells stick together and block small blood vessels. They also don’t last as long as average red blood cells, which last for 120 days. Sickle cells only live for 10-20 days.
Sickle cells versus normal RBS (source)
A parent with or a carrier of the sickle cell trait can pass the trait down to their child. A person born with sickle cell traits from the mother and father has sickle cell anemia. A child with only one of the sickle cell genes is healthy and is only a carrier of the gene.
There is a point mutation on both copies of the Hemoglobin-beta (HBB) gene on chromosome 11. This point mutation causes an amino acid to be changed, and instead of glycine in the genetic code there is serine. This causes Hemoglobin-A to change to Hemoglobin-S and makes red blood cells change from normal to sickle shaped. Because sickle cells are destroyed rapidly in infected bodies, it causes anemia, which causes dizziness, tiredness, and shortness of breath. Other symptoms are acute chest syndrome, jaundice (yellowing of skin, eyes, and mouth), vulnerability to bacterial infections, eye problems, pain/sickle crises, stroke, priapism, and spleen, kidney, and liver damage. These symptoms are caused by the clogging of sickle cells in veins. Sickle Cell Anemia is mostly found in African countries and African Americans. This disease affects 20 million people worldwide and more than 100,000 in the U.S. alone.
In sickle cell disease, a genetic mutation causes red blood cells to take a crescent, or sickle, shape that can block blood vessels. (source)
Discussion/Future direction
Sickle Cell Anemia is a life-long disease, but with the help of modern medicine and research, 50% of patients are able to live past 50. Treatments that have been used for the disease include pain management, antibiotics, and blood transfusions. Currently, the only “cure” is a bone marrow transplant. If a sickle cell patient has a compatible sibling who is willing to do the transplant, it can be done, but there is a lot of risk and only 18% of patients have a compatible sibling. There is a potential cure in gene therapy. Recent studies have tried to correct the defective gene in Hemoglobin and then insert it into the bone marrow of the sickle cell patient. Although there is no definite cure yet, recent studies show lots of promise. There is also base editing where you can replace the nitrogen base in the genetic code for hemoglobin.
_ By: Neerja Bathla _ (External student, guest post on the request of Mentors)
References
- https://www.genome.gov/Genetic-Disorders/Sickle-Cell-Disease
- https://www.hopkinsmedicine.org/health/conditions-and-diseases/sickle-cell-disease
- https://www.nih.gov/news-events/nih-research-matters/fixing-sickle-cell-disease-gene
- https://www.nhlbi.nih.gov/health/sickle-cell-disease
The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of Elio Academy.
