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Sickle cell disease (SCD) isn’t just one condition. It includes several types, based on the specific gene variants a person inherits. Knowing the type can help you better understand possible symptoms, complications, and treatment options.
But finding that information may not always be simple. People who were diagnosed years ago may not have easy access to their medical records, or they may never have had their specific type clearly explained to them. This article covers the different types of SCD, what they may mean for your care, and how to get more information if you’re unsure which type you or your child has.
There are three main types of sickle cell disease:
Different types of sickle cell disease result from different hemoglobin gene combinations. These variants affect which forms of hemoglobin the body makes. All SCD types include hemoglobin S (HbS), an abnormal form that can make red blood cells stiff and sickle-shaped.
Knowing the name of your type can be helpful, but it doesn’t always tell you exactly what living with sickle cell will be like. Symptoms and needs can vary widely, even among people with the same type.
Newborn screening can help identify SCD shortly after birth. If a screening test suggests SCD, healthcare providers use blood tests, such as hemoglobin electrophoresis, to confirm the diagnosis and specific type.
In some cases, genetic testing may also be used. Adults who were diagnosed years ago, people who can’t access their original records, and parents who are unsure of their child’s exact type can ask whether confirmatory testing would be helpful. A hematologist can also explain what the test results mean and how they may affect monitoring and care.
With hemoglobin SS (HbSS), a person inherits a gene that makes hemoglobin S (HbS) from each parent. HbSS (also known as sickle cell anemia) is the most common and usually the most severe type of sickle cell disease.
Because the body produces mostly HbS, red blood cells can become stiff and block blood flow in small blood vessels. This is why HbSS is often linked to more frequent and severe symptoms compared with other types of sickle cell disease.
People with HbSS may experience symptoms such as:
They are also at a higher risk of complications, including:
Not everyone with HbSS will experience all of these symptoms or complications, and how they present can vary from person to person.
Hemoglobin SC (HbSC) develops when a person inherits a gene that makes HbS from one parent and a gene that makes hemoglobin C (HbC) from the other. This leads to both hemoglobin S and hemoglobin C being present in red blood cells.
Compared with HbSS, HbSC is often milder in childhood, although symptoms can vary from person to person. Even so, people with HbSC can experience serious complications that develop or progress over time.
Complications of HbSC can include:
Regular visits with your hematologist can help detect and manage these complications early.
Hemoglobin S/beta-thalassemia develops when a person inherits a gene that makes HbS from one parent and a beta-thalassemia gene variant from the other.
In beta-thalassemia, the body makes less normal hemoglobin than usual. With HbS also present, red blood cells are more likely to become sickle-shaped.
There are two main forms of HbS beta-thalassemia:
In this form, the beta-thalassemia variant means no normal hemoglobin A (HbA) is being produced. It often presents similarly to hemoglobin SS (HbSS), with similar symptoms and complications.
The beta-thalassemia variant allows some HbA to be produced. Symptoms may be milder than with HbSS or HbS beta-zero thalassemia, but severity still varies. Some people with this form may have mild symptoms for long periods, while others may need more regular monitoring and treatment.
Rare types of sickle cell disease occur when a person inherits a gene that makes HbS and another gene that makes a different abnormal form of hemoglobin, such as:
These types vary widely in severity depending on the exact gene combination. Some people may have mild symptoms, while others experience frequent pain crises, anemia, or organ complications.
Sickle cell trait (SCT) is not a form of sickle cell disease. In SCT, a person inherits one gene that makes hemoglobin S, while the other gene makes hemoglobin A (HbA).
Sickle cell trait typically doesn’t cause symptoms, and most people with SCT do not have health problems related to the trait.
Even so, it’s important to know your sickle cell status. Because SCT is inherited, people with SCT can pass the gene variant to their children. If both parents have SCT, each pregnancy has a 25 percent chance that the child will have sickle cell disease.
Sickle cell trait can also cause red blood cells to briefly sickle in situations like:
Rare complications associated with SCT include:
Knowing your sickle cell disease type can offer helpful information, but it doesn’t tell the whole story. Two people with the same type of SCD may have very different symptoms and complications. Other factors can affect how the disease shows up, including:
That’s why regular follow-up with a hematologist is important, even for people whose condition has been described as “milder.”
Knowing your SCD type can help healthcare providers understand which complications to watch for and what monitoring may be appropriate. Treatment also depends on your symptoms and overall health, not just your SCD type.
Some people may need medicines to reduce pain crises, while others may need blood transfusions or treatment for complications. Even types often described as milder can still cause serious health problems, so ongoing care is important.
If you or your child has sickle cell disease, ask your doctor what type you have and what it means for symptoms, monitoring, and treatment.
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