What is Sickle Cell Disease?

If your child has been diagnosed with Sickle Cell Disease (SCD), you probably have many questions and issues to deal with besides stroke. But stroke can be a serious complication for SCD children.

SCD (Sickle Cell Disease)
SCD describes a group of inherited blood disorders, with sickle cell anemia (also called SS disease or sicklemia) being the most prevalent and best-known disorder. SCD was first described in 1910 by Dr. James Herrick of Chicago, who hypothesized that his patients' symptoms came from the sickle-shaped red blood cells he observed through his microscope.

It was later discovered that sickled red blood cells had a diminished ability to carry oxygen. We now know that abnormal genes in hemoglobin (the oxygen carrying protein inside red blood cells) are to blame.

SCD and Blood Circulation
Normal red blood cells are round and flexible, and flow smoothly through the smallest veins. In SCD, however, hemoglobin molecules contain a set of abnormal amino acids that cause an abnormal reaction to transporting oxygen throughout the body.

While normal red blood cells take up oxygen from the lungs and dispense it throughout the body, sickled red blood cells contain abnormal hemoglobin molecules. These faulty molecules retain their normal shape when they take up oxygen from the lungs; but when they disperse it, they stick together and form long, twisted (braided) chains, in a process called polymerizing that deforms the red blood cells. These red blood cells continue polymerizing and depolymerizing until their membranes are no longer soft, flexible, and round, but hard, stiff, and sickle-shaped. These sickled cells can no longer move freely through the smaller arteries and veins; instead, they clump together and stick to vessel walls. The results can include pain throughout the body, damage to organs, and strokes.

Inheritance of SCD Traits
There is a significant difference between having the sickle cell trait and having SCD. Merely having the trait does not manifest itself in any symptoms. If a child inherits a sickle gene from one parent and a normal gene from the other, the child will carry the sickle cell trait, but will not have active disease. But a child who inherits sickle genes from both parents will be born with SCD. Parents from populations at risk for SCD may want to undergo genetic counseling before deciding whether to have children.

SCD in America is predominantly a disease of African Americans, but may affect others of Mediterranean, Middle Eastern, and Central Asian ancestry. In the U.S., about one in every twelve African Americans carries the sickle cell trait, and one in every 400 African Americans is born with SCD. Worldwide, one in every 250,000 babies born annually has SCD.

Emergence of SCD
Until 1970, Sickle Cell Disease (SCD) remained in the background compared to other diseases. While the number of SCD cases diagnosed in the U.S. was equal to the number of cystic fibrosis cases, and exceeded the number of muscular dystrophy cases diagnosed by over 40%, the funds raised to assist with these diseases were in the ratio of 1:40:144, and grants given by the National Institutes of Health (NIH) for research in these conditions were in the ratio of 1:3:3. In 1970, two publications by Dr. Robert Scott of Virginia helped change this and focus more attention on SCD.

The National Sickle Cell Anemia Control Act, passed by Congress on May 16, 1972, increased funds towards the research, education, screening, and counseling of carriers of the sickle cell trait. Population screening detected the sickle cell trait with a view to genetic counseling, monitoring, and treatment. Screening at birth was implemented in 42 out of the 53 states.

Next: Stroke and Sickle Cell Disease

Last Updated: October 31, 2006