What is sickle cell disease?
Sickle cell disease is a group of inherited red blood cell disorders affecting millions of individuals throughout the world. The CDC estimates that approximately 300,000 people worldwide have sickle cell disease, with about 100,000 in the United States. Sickle cell disease is associated with an increased risk of early death and has adverse clinical complications impacting various organ systems. In turn, patients with sickle cell disease and their families report significantly diminished quality of life from childhood to adulthood.
Understanding the different variants of sickle cell disease is important. If you are treating a patient at a hospital or in a school setting, it is important to understand what they might be experiencing based on their variant of sickle cell disease and how that may impact clinical treatment.
There are several types of sickle cell disease. The most common ones are:
- Hemoglobin SS (Sickle cell anemia)
- Hemoglobin SC (Sickle C disease)
- Hemoglobin SB + (Sickle beta thalassemia)
- Hemoglobin SB 0 (Sickle beta zero thalassemia)
- Hemoglobin SD, SE, SO (Sickle D, E, or O disease)
Sickle cell anemia, type SS, occurs when a child inherits one substitution beta-globin gene, the sickle gene, from both parents. This child has what is commonly called sickle cell anemia. Populations with a high frequency of sickle cell anemia are of African and Indian descent. This is considered the most severe type of sickle cell disease because the person has both SS genes. They experience severe anemia and severe pain because most of the red blood cells in their body are sickle-shaped.
The next variant is Hemoglobin SC. These are individuals with sickle hemoglobin C. They have a slightly different substitution in their beta-globin gene that produces both hemoglobin C and hemoglobin S. Sickle hemoglobin C disease may cause similar symptoms as sickle cell anemia but because they don't have both SS genes, there is less anemia. Populations with a high frequency of sickle hemoglobin C disease are those of West African, Mediterranean, and Middle Eastern descent.
Individuals with sickle beta thalassemia disease, both + and 0, have substitutions in both beta-globin genes. The severity of this disease will vary in patients according to the amount of normal beta-globin they can produce. When no beta-globin is produced, these patients' symptoms will be identical to sickle cell anemia, with the most severe cases needing chronic blood transfusions. Populations with a high frequency of sickle beta thalassemia are of Mediterranean and Caribbean descent.
Sickle hemoglobin O disease is another substitution in the beta-globin gene that interacts with sickle hemoglobin. Why is that important? Because even if you don't have the sickle trait but have hemoglobin O and you have a child with someone who does have the sickle trait, the hemoglobin O interacts with that sickle hemoglobin. So, individuals with sickle hemoglobin O have similar symptoms of sickle cell anemia. Populations with a high frequency of sickle hemoglobin O disease are of Arabian, North African, and Eastern Mediterranean descent.
With sickle hemoglobin D disease, a different substitution of the beta-globin gene has been found to interact with the sickle hemoglobin gene. Individuals with sickle hemoglobin D have moderately severe anemia and occasional pain episodes. Populations with a high frequency of sickle hemoglobin D are those of Asian and Latin American descent.
This ATE is an excerpt from the course Sickle Cell Disease Management: The Role of SLPs and Audiologists, Part 1, presented by Candice J. Adams-Mitchell, SLP.D, CCC-SLP.