Why are there different types of sickle cell?
“Sickle cell disease” is an umbrella term used to describe a group of genetic diseases that affect the body’s hemoglobin. Hemoglobin is the protein in red blood cells that carries oxygen. It is made up of 2 alpha globin chains and 2 beta globin chains. Sickle cell disease is caused by a mutation in the beta globin gene, resulting in an abnormal hemoglobin called sickle hemoglobin, or Hb S. Different types of sickle cell disease arise based on whether the hemoglobin beta S gene is inherited with another beta S gene or with a different beta gene mutation.
The Main Types of Sickle Cell Disease:
Hemoglobin SS Disease
Hemoglobin SS disease is the most common and most severe type of sickle cell disease. It occurs when you inherit the hemoglobin S gene mutation from both parents. In this type, the body only produces hemoglobin S. This type is often called “sickle cell anemia.”
Hemoglobin SB 0 (beta zero) Thalassemia
Hemoglobin S beta zero thalassemia occurs when you inherit the hemoglobin beta S gene from one parent and a hemoglobin beta0 thalassemia gene mutation from the other parent. It has similar symptoms to hemoglobin SS disease and is also called sickle cell anemia because the body only produces hemoglobin S.
Hemoglobin SC Disease
Hemoglobin SC disease is the second most common type of sickle cell disease. It occurs when you inherit the hemoglobin beta S gene from one parent and the hemoglobin C gene from the other. Individuals with hemoglobin SC disease may have similar symptoms to individuals with hemoglobin SS disease. However, the symptoms may be less severe.
Hemoglobin SB+ (beta) Thalassemia
Hemoglobin SB+ (beta) thalassemia occurs when you inherit the hemoglobin beta S gene from one parent and a hemoglobin beta plus thalassemia gene from the other parent. In this type, some normal beta hemoglobin is produced, but in reduced amounts. Because the body produces some normal hemoglobin, this form of sickle cell disease is less severe than hemoglobin SS disease. Symptoms are usually milder than hemoglobin SS or SC disease, but complications can still develop.
Hemoglobin SD, Hemoglobin SE, and Hemoglobin SO
These types of sickle cell disease are less common and are usually less severe.