Download What Causes Sickle Cell Anemia?

Sickle Cell Anemia
What Causes Sickle Cell Anemia?
An inherited condition that is autosomal
recessive
• People with Sickle Cell Anemia inherit two
copies of the recessive sickle cell gene (S), one
from each parent.
• The sickle cell gene makes abnormal
hemoglobin.
• The abnormal hemoglobin clumps together when
it gives up its oxygen. These clumps are crystals
that cause red blood cells to become shaped like
a sickle, instead of the normal disk shape.
•
What Causes Sickle Cell Trait?
• People who inherit only one copy of the sickle
cell gene (from one parent) will not have Sickle
Cell Anemia. They will have Sickle Cell Trait.
• People with Sickle Cell Trait generally have no
symptoms and lead normal lives. Like people
with Sickle Cell Anemia, however, they can
pass the sickle cell gene on to their children.
• People with Sickle Cell Trait are also resistant
to Malaria, leading to an increase in this
genotype and phenotype.
Inheritance Pattern
Malaria and Sickle Cell Trait
• People with normal hemoglobin A are
susceptible to death from malaria.
• People with Sickle Cell Anemia are susceptible
to death from the complications of their disease.
• People with Sickle Cell Trait, who have one
gene for hemoglobin A and one gene for
hemoglobin S, have a greater chance of
surviving malaria and do not suffer adverse
consequences from the hemoglobin S gene.
• People who have
Sickle Cell Trait
are resistant to
Malaria.
• Therefore, Malaria
is causing an
increase in the
number of people
who have Sickle
Cell Trait.
Prevalence of Sickle Cell
• Sickle hemoglobin is found in people whose
ancestors come from Africa, the Arabian States,
South India and from countries around the
Caribbean Sea, such as Puerto Rico, Cuba,
Haiti and Jamaica, and also from countries
around the Mediterranean Sea, such as Italy,
Cyprus, Greece, Turkey, and Syria.
• Sickle Cell Trait occurs in approx. 1 in 12 (8%)
African-Americans. Sickle cell anemia occurs in
approx.1 in 375 African-Americans and affects
more than 50,000 Americans in total.