Sickle Cell Disease

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by Dinesh1
Last updated 6 years ago

Cell Biology

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Sickle Cell Disease

Sickle Cell Disease

Testing and Screening:Every state in the United States, the District of Columbia, and the U.S. territories require that every baby is tested for SCD as part of a newborn screening program. Blood from a heal prick is analyzed in a lab for unnormal hemoglobin. Confiming lab tests are conducted by examinng blood under a microscope to check for large amounts of sickle cells.

Genetics of SCD:Mutations in the HBB gene, which has been sequenced, cause sickle cell disease. The hemoglobin protein in red blood cells are affected. The HBB gene is located from base pair 5,225,465 to base pair 5,227,070 on chromasome 11 and is 1,605 bp long. There are hundereds of variations on this gene, and some produce noticeable changes, while others have no affect. The most common of the diseases, sickle cell anemia, is caused by a mutation that results in the production of an abnormal version of beta-globin called hemoglobin S or HbS. The mutation replaces a single amino acid glutanic acid with valine. This change causes the abnormal hemoglobin S subunits to stick together and form rigid molecules that bend the red blood cells into a sickle shape. Hemoglobin C, particularly common in West Africans, has a change from glutanic acid to lysine in the 6th position. Hemoglobin E, more commonly found in Southeast Asian populations, has the same change in the 26th position.

Symptoms of Sickle Cell Disease includeEpisodes of pain, Hand-foot syndrome, a swelling of the limbs of babies, frequent infections, delayed growth, vision problems, and Anemia, a shortage of red blood cells. Due to recent ability to treat the symptoms, average life expectancy is mid-40s.

By Dinesh Das Gupta

Video Summary

About Sickle Cell DiseaseOn November 15, 1910 in Chicago, Dr. James Herrick made the first official description in published literature of sickle cell disease when examing the blood of a medical student from Granada. Sickle Cell Disease (SCD) is caused by an autosomal recessive inherited gene that produces sickle or cresent shaped red blood cells instead of round and smooth ones. These irregularly shaped cells can get stuck in small blood vessels, slowing or stopping blood flow to these areas. There is no permanent cure besides risky bone marrow stem cell transplants. Other treatments can alliviate pain and help prevent problems associated with sickle cell anemia. SCD affects 90,000 to 100,000 Americans. Although women and men inherit the disease at equal frequencies, African-Americans are disproportionately affected. 1/12 have the sickle cell trait.

Did you know?People with a heterozygous set of allels have an increased resistance to malaria

Did you know?Sickle cell disease is the most common genetic disorder in the United States

Treatment:The only cure for SCD presently availible is Hematopietic Stem Cell Transplantaion. This procedue takes stem cells from the bone marow or blood of a person who does not have the sickle cell disease and replaces those within the sick person's body. The person's original bone marrow stem cells will be treated with drugs to destroy them or decrease their number. The donor stem cells are then injected into the vein with the hope tha they can make a new home and gradually replace the mutated cells. In children where all proteins and immune system markers match with the donor cells, there is about an 85% success rate. About 5% of people have died. Other then that, there is an oral medicine called Hydroxyurea. This drug has been shown to reduce or prevent several SCD complications by increasing the amount of hemoglobin F, which conters the effects of hemoglobin S.


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