Download Sickle Trait and Sickle Cell Disease People can dream, but their

Sickle Trait and Sickle
Cell Disease
People can dream, but their road to success can
be derailed in the most unusual ways, perhaps
none as strange as that which affected Ryan
Clark of the Pittsburgh Steelers. When his team
plays in Denver, the Mile High City, so named
because it sits at an altitude of 5,280 feet, Clark
is sidelined. This is because of an incident in
2007 in which Clark ended up critically ill
requiring emergency surgery because of his
genetics; he suffers from sickle trait, a condition
that affects the shape and function of red blood
cells. So when his teammates compete in the
Mile High City, Clark is relegated to the
sidelines.
Red blood cells are manufactured in the bone marrow. Their unique biconcave shape
(think of squeezing a marshmallow between your fingers) increases their storage
capacity for hemoglobinmolecules that carry oxygen. They also make the cells pliable
and soft so they can squeeze through the tiniest blood vessels in the body. In sickle
disease, the red blood cells form an abnormal crescent shape that is rigid, causing the
red blood cells to be damaged. The cells aren't malleable enough to get through tight
spaces, and this can increase the risk of forming blood clotsin the small capillaries of
different organs causing the potential for organ damage...
What is sickle cell anemia?
Sickle cell anemia (sickle cell disease) is a disorder of the blood caused by an
inherited abnormal hemoglobin (an oxygen-carrying protein within the red blood
cells). The abnormal hemoglobin causes distorted (sickled) red blood cells. The
sickled red blood cells are fragile and prone to rupture. When the number of red blood
cells decreases from rupture (hemolysis), anemia is the result. This condition is
referred to as sickle cell anemia. The irregular sickled cells can also block blood
vessels causing tissue and organ damage and pain.
Sickle cell anemia is one of the most common inherited blood anemias. The disease
primarily affects Africans and African Americans. It is estimated that in the United
States, some 50,000 African Americans are afflicted with the most severe form of
sickle cell anemia. Overall, current estimates are that one in 1,875 U.S. African
American is affected with sickle cell anemia.
How is sickle cell anemia inherited?
Sickle cell anemia is inherited as an autosomal (meaning that the gene is not linked to
a sex chromosome) recessive condition whereas sickle cell trait is inherited as an
autosomal dominant trait. This means that the gene can be passed on from a parent
carrying it to male and female children. In order for sickle cell anemia to occur, a
sickle cell gene must be inherited from both the mother and the father, so that the
child has two sickle cell genes.
The inheritance of just one sickle gene is called sickle cell trait or the "carrier" state.
Sickle cell trait does not cause sickle cell anemia. Persons with sickle cell trait usually
do not have many symptoms of disease and have normal hospitalization rates and life
expectancies. Sickle cell trait is present in some two million blacks in the United
States (8% of the U.S. black population at birth). When two carriers of sickle cell trait
mate, their offspring have a one in four chance of having sickle cell anemia. (In some
parts of Africa, one in five persons is a carrier for sickle cell trait.)