Ryan Clark, a professional football player, always knew he was a carrier for sickle cell disease, called sickle cell trait. Then, during an away game in Denver, Colorado, Clark felt a sharp pain in his left side. He ended up in the hospital with a splenic infarction, a life-threatening condition normally seen in patients with sickle cell disease.
He didn’t know it, but by changing altitudes and playing football, Clark had created a dangerous scenario for someone with sickle cell trait.
After Clark’s spleen and gall bladder were removed, he recovered. He even continued to play in the NFL. But he never played in Denver again.
For many of his fans, it was the first they’d heard of sickle cell trait or that it can cause symptoms.
We talked to Emily Moses, MD, from UVA Health Children’s Comprehensive Sickle Cell Clinic, about the differences between having sickle cell disease and having sickle cell trait.
Sickle Cell Trait vs Sickle Cell Disease
Sickle cell disease (SCD) is probably the most well-known inherited blood disorder. Sickle cell disease affects roughly 100,000 people in the U.S. And sickle cell trait (SCT) affects 2 million Americans.
That means for every 1 person who has sickle cell disease, 20 are carriers. But even though it’s significantly more common, most people know less about SCT. And many people with SCT don’t even know they have it.
In contrast, most people with sickle cell disease know they have it. It’s part of the newborn screening, and the symptoms are hard to miss. But SCT signs can be a lot more subtle. Though less likely to cause serious symptoms, some medical complications do come from living with SCT.
Recessive Genes & Carriers
Sickle cell disease is a recessive gene. That means most of the time, it comes from having 2 copies of the sickle cell gene. This gene affects hemoglobin, a protein needed for red blood cells. Other, rarer, types have a copy of the sickle cell gene and another abnormal hemoglobin gene.
But with sickle cell trait, you have one copy of the sickle cell gene. The other hemoglobin gene is healthy and that’s enough for healthy red blood cells. That’s why people with sickle cell trait don’t usually have symptoms.
For many people, the most concerning part of SCT is finding out that if they have sickle cell trait, they’re a carrier. Which means their children are at risk for sickle cell disease.
Does Sickle Cell Trait Cause Symptoms?
“Almost never,” Moses says.
But if you have SCT, you should be aware of some risks. For instance, if your body suddenly needs more oxygen, your recovery might be slower than other people’s.
For instance, you’d need more oxygen when:
- Doing high-intensity physical activity
- Traveling to high elevations
- Riding in an unpressurized airplane
- Scuba diving
So, for Ryan Clark, traveling to Denver (higher elevation) and playing football (high intensity workout), triggered his SCT symptoms.
Fortunately, he was able to get the help he needed.
Wondering If You Have Sickle Cell Trait?
A genetics counselor can help you understand your risk, and figure out your next steps.
Can Sickle Cell Trait Turn into Sickle Cell Disease?
No, it can’t. Even though it can become serious, SCT doesn’t become sickle cell disease or sickle cell anemia, a type of sickle cell disease. When Clark recovered from his medical emergency, he still only had SCT.
Whether you're a carrier or have sickle cell disease is determined by the genes you’re born with. These don’t change. The difference between “trait” and “disease” isn’t one of severity.
Sometimes people with sickle cell trait think if they have anemia, it’s the same as “sickle cell anemia.” But anemia and sickle cell anemia aren’t the same thing.
Anemia vs Sickle Cell Anemia
Anemia is actually a pretty common condition. But the cause of sickle cell anemia isn’t. For most people, anemia is caused by iron deficiency. That’s not the case for sickle cell disease.
“You don’t want to take iron for sickle cell disease,” Moses says. “You can actually overload on iron, and since that’s not the cause, it won’t help.”
If you have SCD, your body loses red blood cells continually, because those cells self-destruct. Healthy red blood cells have a 120-day lifespan. Sickled cells only survive an average of 15 days. Iron supplements can’t fix this issue.
People with SCD often need blood transfusions to recover.
Can People with SCT Donate Blood?
Because sickle cell runs in families, one question that comes up frequently is if people with sickle cell trait can be blood donors. Yes you can!
People with SCT can even donate bone marrow. Bone marrow transplants can cure sickle cell disease.
For many families who have a loved one with sickle cell disease, a bone marrow transplant from a relative with SCT is the perfect match. And still offers a cure.
Medical Tests with SCT
SCT leaves your blood cells with full functionality. But SCT makes your blood cells behave just a little bit differently. Whenever doing medical tests or lab work, make sure your provider knows you have SCT.
This is especially true for diabetes testing.
What About Sickle Cell Trait & Malaria?
Having SCT offers a slight benefit if you get malaria. You’re less likely to get very sick from malaria. And you have a 30% improvement on survival.
But ideally, you want to avoid getting malaria at all, even if you are likely to survive it.
So, even if you have SCT, don’t take the risk. If you’re traveling somewhere with malaria, talk to your doctor about an antimalarial medication. And stock up on insect repellant.
On the other hand, if you have sickle cell disease, you’re more likely to get seriously ill from malaria.
Check out this toolkit for understanding SCT.
Having Children with Sickle Cell Trait
Of course, one of the big reasons you’d want to get tested for sickle cell trait is if you’re having children.
If your partner doesn’t have sickle cell trait, you’ll have a 25% chance of passing on SCT. If you and your partner both have sickle cell trait, you’ll have a 50% chance of passing on SCT and a 25% chance of having a child with sickle cell disease.
If your partner has a different blood disorder, you could still have a child with sickle cell disease. If someone with SCT and someone with thalassemia had children, they'd have a 25% chance of having a child with sickle cell disease.
Over 65% of people with sickle cell disease have a type caused by two sickle cell trait genes. But all the other types are caused by one sickle cell gene and one other abnormal hemoglobin gene. This is most often associated with thalassemia, but there are other, rarer, variations.
If you have SCT, you may want to consider genetic testing. Genetic counselors can help you talk through options and get the right genetic testing. For most people, being a sickle cell carrier is rarely a barrier to having children.
