Sickle cell disease is a group of conditions passed down in families through their genes. The type of sickle cell disease a person has depends on the hemoglobin genes each parent passes down to them. Hemoglobin is the protein inside red blood cells that carries oxygen. Someone with sickle cell disease has at least one sickle cell gene. The other hemoglobin gene can be either another sickle cell gene or a gene for a different type of abnormal hemoglobin. The genes cause the body to make hemoglobin that causes the red blood cells to become sickle shaped. 

Here’s how sickle cell genes can run in families:

• A child who gets two sickle cell genes, one from each parent, will have sickle cell disease.
• A child who gets a sickle cell gene from one parent and a normal hemoglobin gene from the other parent has sickle cell trait. Most people with sickle cell trait don't have symptoms, but they can pass the sickle cell gene to their children.
• Someone who gets a sickle cell gene from one parent and another kind of abnormal gene from the other parent may have a different form of sickle cell disease, such as hemoglobin SC disease or sickle beta thalassemia.