Sickle Cell Disease vs. Trait: What’s the Difference?

Our genes define so much about us. Our eye color. Our nose shape. Our dimples, or lack thereof.

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They can also affect your health and your risk for certain diseases. So, when you hear that sickle cell disease runs in families, you might worry.

But how is sickle cell trait different from sickle cell disease? How are they inherited? And what’s the risk in your family?

Hematologist Ravi Talati, DO, breaks down sickle cell trait vs. sickle cell disease.

Differences between sickle cell trait and sickle cell disease

The difference between sickle cell trait and sickle cell disease comes down to your genes and how they affect your body and your life.

Genetics

Sickle cell disease and sickle cell trait both stem from a genetic variation (mutation) in the HBB gene. That’s a gene that affects how your body makes hemoglobin — a protein in your red blood cells that carries oxygen.

You inherit two copies of the HBB gene: One from your biological mother and one from your biological father.

“People with sickle cell trait inherited a mutated HBB gene from one parent and not the other,” Dr. Talati explains. “People with sickle cell disease inherit mutated HBB genes from both parents.”

Let’s take a look at the odds:

Parent 1	Parent 2	Child’s risk
No trait	Sickle cell trait	50% sickle cell trait; 50% no trait
No trait	Sickle cell disease	100% sickle cell trait
Sickle cell trait	Sickle cell trait	50% sickle cell trait; 25% sickle cell disease; 25% no trait
Sickle cell trait	Sickle cell disease	50% sickle cell trait; 50% sickle cell disease
Sickle cell disease	Sickle cell disease	100% sickle cell disease
Parent 1
No trait
Parent 2
Sickle cell trait
Child’s risk
50% sickle cell trait; 50% no trait
No trait
Parent 2
Sickle cell disease
Child’s risk
100% sickle cell trait
Sickle cell trait
Parent 2
Sickle cell trait
Child’s risk
50% sickle cell trait; 25% sickle cell disease; 25% no trait
Sickle cell trait
Parent 2
Sickle cell disease
Child’s risk
50% sickle cell trait; 50% sickle cell disease
Sickle cell disease
Parent 2
Sickle cell disease
Child’s risk
100% sickle cell disease

Sickle cell trait can’t turn into sickle cell disease — you’re born with one or the other.

The American Society of Hematology estimates that sickle cell disease affects between 1 million and 3 million people in the United States. Anyone can be affected, but it’s more prevalent in people who are Black. More than 100 million people in the world have sickle cell trait.

Symptoms

Healthy red blood cells are flexible and shaped like doughnuts. That helps them flow through your body easily. They can bump into each other and against the sides of your blood vessels without any problems, like inner tubes flowing down a lazy river.

People with sickle cell trait have mostly round, healthy red blood cells.

But that’s not the case with people with sickle cell disease. The mutated HBB genes cause their bodies to create red blood cells that are shaped like a semi-circle — or like a farm tool called a sickle (hence the name).

Sickle-shaped blood cells don’t flow as well. They can stick together. And that can cause symptoms, like:

Pain
Fatigue
Weakness
Swelling

The symptoms of sickle cell disease can vary from relatively mild to severe. And they can flare up at times and be better at others.

There’s some scientific debate about whether having sickle cell trait can affect your health and well-being. Many times, people with sickle cell trait can go through their whole lives without ever having symptoms.

“As far as we know so far, having sickle cell trait shouldn’t cause any symptoms — but we’re doing studies to better understand whether that’s always true,” Dr. Talati reports.

For example, there are some theories that very intense physical activity or dehydration may, rarely, cause severe complications for people with sickle cell trait. But more research is needed.

The importance of testing

Genetic testing can help you understand how your sickle cell status can affect your future children. Even if sickle cell trait doesn’t affect your health, it could affect theirs.

Babies born in U.S. hospitals are screened for hemoglobin disorders at birth, including sickle cell trait and disease. And Dr. Talati says genetic testing for parents prior to pregnancy is available, too.

“We encourage people with sickle cell trait and sickle cell disease to do genetic testing with their partner and consider genetic counseling to understand the risks,” he advises.

For people living with sickle cell disease, there is good news: New treatments can help.

“You can live a very healthy and fruitful life. We have methods of managing and preventing complications now more than ever,” Dr. Talati encourages. “When started early, treatment can reduce pain crises and hospital visits — and improve long-term outcomes.”

If you’re concerned about how sickle cell trait or disease affects you or your family, talk with a healthcare provider, like a hematologist or genetic counselor. They can help you understand your risk and help you live your fullest life.

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