Sickle Cell Anemia Factsheet

Sickle Cell Anemia Factsheet

Angus Kong, Shahrukh Alvi, David Venuto

Genetic Information

Sickle cell anemia, a common form of sickle cell disease is an autosomal recessive genetic disorder caused by a mutation in the HBB gene, which codes for hemoglobin. The presence of two defective genes (SS) is needed for sickle cell anemia. This mutation results in the production of an abnormal version of beta-globin called hemoglobin S. In this condition, hemoglobin S replaces both beta-globin subunits in hemoglobin. In the human β-globin locus or in region 15.5 on the short arm (p) of chromosome 11, the 6th positioned codon or what normally is the GAG codon is mutated into a GTG codon. By transcription, the GTG codon becomes a GUG codon. As a result, The hydrophobic amino acid valine takes the place of hydrophilic glutamic acid at the sixth amino acid position of the HBB polypeptide chain. This substitution creates a hydrophobic spot on the outside of the protein structure that sticks to the hydrophobic region of an adjacent hemoglobin molecule's beta chain. This clumping together (polymerization) of hemoglobin S molecules into rigid fibers causes the "sickling" of red blood cells. The sickle-shaped cells die prematurely, which can lead to a shortage of red blood cells (anemia). The sickle-shaped cells can also block small blood vessels, causing pain and organ damage.

Diagnosis

• Complete blood count
• Hemoglobin electrophoresis to detect different types of hemoglobin
• A blood smear can be viewed under a microscope to determine if there is a presence of sickle shaped cells.
• Amniocentesis can be used to identify the trait in unborn children.

Canada screens all newborn babies for sickle cell anemia after birth.

Symptoms

The common symptoms include: attacks of abdominal pain, bone pain, breathlessness, delayed growth and puberty, fatigue, fever, paleness, rapid heart rate, ulcers on the lower legs (in adolescents and adults), andyellowing of the eyes and skin (jaundice).

Treatment

There is no cure for sickle cell anemia but certain procedures and drugs can greatly aid those affected by sickle cell anemia. Blood transfusions, oral antibiotics, and hydroxyurea are effective for the treatment of sickle cell anemia.Blood transfusions correct anemia by increasing the number of normal red blood cells in circulation.Oral antibiotics prevent pneumococcal infection and early death in children diagnosed with sickle cell anemia.Hydroxyurea is first effective drug treatment for adults by reducing the frequency of painful crises and acute chest syndrome.

Sources:

Human Genome Project Information -

U.S. National Library of Medicine -