Sickle Trait and Sickle Cell Disease

Medical Author: Benjamin Wedro, MD, FACEP, FAAEM
Medical Editor: Melissa Stöppler, MD

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 hemoglobin molecules 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 clots in the small capillaries of different organs causing the potential for organ damage.

Picture of Sickle Cell Red Blood Cell
Sickle Cell Red Blood Cell

Sickle cell disease is a genetic disease that most commonly affects people whose heritage is usually African or Caribbean. Patients with full blown sickle cell anemia have inherited a sickle gene from each parent and are usually diagnosed in childhood as having this autosomal recessive disease. Autosomal means that the gene is not located on either the X or Y sex chromosome. Recessive means that you need to have two copies of the involved gene to have the disease. If only one parent passes on that “bad gene,” the disease may not be present, or in the case of sickle disease, the patient is said to have sickle trait. People with sickle trait usually live normal lives and have very few, if any, symptoms. Unfortunately, that is not always the case.