Sickle Cell

Sickle cell anemia is one of a group of inherited disorders known as sickle cell disease. It affects the shape of red blood cells, which carry oxygen to all parts of the body.

Sickle cell disease (SCD) is a group of inherited red blood cell disorders. Red blood cells contain hemoglobin, a protein that carries oxygen. Healthy red blood cells are round, and they move through small blood vessels to carry oxygen to all parts of the body. In someone who has SCD, the hemoglobin is abnormal, which causes the red blood cells to become hard and sticky and look like a C-shaped farm tool called a “sickle.” The sickle cells die early, which causes a constant shortage of red blood cells. Also, when they travel through small blood vessels, they get stuck and clog the blood flow. This can cause pain and other serious complications (health problems) such as infection, acute chest syndrome and stroke.

Types of SCD

There are several types of SCD. The specific type of SCD a person has depends on the genes they inherited from their parents. People with SCD inherit genes that contain instructions, or code, for abnormal hemoglobin.

Below are the most common types of SCD:

HbSS

People who have this form of SCD inherit two genes, one from each parent, that code for hemoglobin “S.” Hemoglobin S is an abnormal form of hemoglobin that causes the red cells to become rigid, and sickle-shaped. This is commonly called sickle cell anemia and is usually the most severe form of the disease.

HbSC

People who have this form of SCD inherit a hemoglobin “S” gene from one parent and a gene for a different type of abnormal hemoglobin called “C” from the other parent. This is usually a milder form of SCD.

HbS beta thalassemia

People who have this form of SCD inherit a hemoglobin “S” gene from one parent and a gene for beta thalassemia, another type of hemoglobin abnormality, from the other parent. There are two types of beta thalassemia: “zero” (HbS beta⁰) and “plus” (HbS beta⁺). Those with HbS beta⁰-thalassemia usually have a severe form of SCD. People with HbS beta⁺-thalassemia tend to have a milder form of SCD.

There also are a few rare types of SCD, such as the following:

HbSD, HbSE, and HbSO

People who have these forms of SCD inherit one hemoglobin “S” gene and one gene that codes for another abnormal type of hemoglobin (“D”, “E”, or “O”). The severity of these rarer types of SCD varies.

Sickle Cell Trait (SCT)

HbAS

People who have sickle cell trait (SCT) inherit a hemoglobin “S” gene from one parent and a normal gene (one that codes for hemoglobin “A”) from the other parent. People with SCT usually do not have any of signs of the disease. However, in rare cases, a person with SCT may develop health problems; this occurs most often when there are other stresses on the body, such as when a person becomes dehydrated or exercises strenuously. Additionally, people who have SCT can pass the abnormal hemoglobin “S” gene on to their children.