Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
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
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...