Marvin Reid Ph.D., Contributor
Left: Normal red blood cells as seen under a microscope. Right: Sickled red blood cells. - CONTRIBUTED PHOTOS
SICKLE CELL disease is a genetic disease of the blood. It is called a genetic disorder because the only way to get it is if one gets the sickle cell genes from one's parents. Therefore, sickle cell disease is not catching, that is, you will not get it by touching, hugging or sharing of personal items.
In order to understand more clearly how one gets sickle cell disease, it is essential to review how we acquire characteristics from our parents.
Each person receives genetic material from each parent. This combined genetic material makes up the genotype of the child. It determines what the child will look like, what colour hair it will have, how tall he will be, what kind of blood he will have, etc. The gene contains the code or blueprint which controls the make-up of body components.
In sickle cell disease, the gene that codes for the haemoglobin protein is abnormal. Haemoglobin is found mainly in red blood cells and its primary purpose is transport oxygen to tissues.
The most common type of haemoglobin found in healthy people is haemoglobin A. Normal red blood cells with haemoglobin A are soft and round which allows them to squeeze through tiny blood vessels and they last for about 120 days before new ones replace them.
Persons with sickle cell disease have red blood cells that contain mostly haemoglobin S, an abnormal type of haemoglobin. These red blood cells are prone to become sickle-shaped (half-moon shaped) and these sickled cells have difficulty passing through small blood vessels thus causing blockage of the blood vessels. When sickle-shaped cells block small blood vessels, less blood can reach that part of the body. Tissue that does not receive a normal blood flow eventually becomes damaged.
CAUSES FO ANAEMIA AND JAUNDICE
In addition, the abnormal sickle red cells are destroyed faster and have to be replaced by the body after only two to three weeks. The clinical end result of this rapid destruction of the red cells is anaemia (weak blood) and jaundice (yellowing of the eyes).
There are several types of sickle cell disease. The most common types and the frequency in which they occur in Jamaica are:
Homozygous sickle cell disease (SS) - one case in every 300 births;
Sickle-haemoglobin C disease (SC) - one case in every 500 births;
Sickle beta-plus thalassemia - one case in every 3,000 births;
Sickle beta-zero thalassemia. - one case in every 7,000 births.
To some extent the severity of illness is dependent upon the type of sickle cell disease that one has. Individuals with Homozygous sickle cell disease (SS) and sickle beta-zero thalassemia tend to have a more severe disease course than the others.
WHAT IS SICKLE CELL TRAIT?
Sickle cell trait (AS) is an inherited condition in which both haemoglobin A and S are produced in the red blood cells, always more A than S. Sickle cell trait is not a type of sickle cell disease. People with sickle cell trait are generally healthy. Approximately 10 per cent of Jamaicans will have the sickle cell trait. The importance of the trait is that an individual with the trait may pass on the abnormal sickle cell gene to their offspring. If two individuals with sickle cell trait have a child, there is 25 per cent chance that the child will have sickle cell disease.
