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), and yellowing 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 http://www.ornl.gov/sci/techresources/Human_Genome/posters/chromosome/sca.shtml
U.S. National Library of Medicine - http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001554/