Sickle cell disease, an inherited chronic disease, affects the shape of red blood cells. While normal red blood cells are round and pliable, individuals with sickle cell disease have some red blood cells that are rigid and shaped like sickles or crescent moons. These sickle cells can slow down or block blood flow throughout the body.
Asmaa Ferdjallah, M.D., M.P.H., a Mayo Clinic specialist in pediatric hematology and bone marrow transplants, says, “In the past, sickle cell disease was an exclusively fatal disease. Most kids didn’t survive into adulthood.”
Luckily, with today’s treatments, people with sickle cell disease can live long and rewarding lives. Dr. Ferdjallah explains, “When individuals with sickle cell disease manage their disease with medication, their lifespan mirrors the average lifespan. Patients with sickle cell disease, even very severe sickle cell disease, are living far into adulthood — into their fifth and sixth decade, which was unheard of before.”
How do you know if you have sickle cell disease?
In the U.S., all babies born in a medical facility are automatically screened for sickle cell disease as part of the universal newborn screening program. A blood test checks for the presence of a specific type of hemoglobin. Hemoglobin is a protein in red blood cells that carries oxygen throughout the body.
According to Dr. Ferdjallah, “If you are born here in the United States, and you have sickle cell disease, you will be picked up on a newborn screen and be immediately referred to a list of health providers that have expertise in sickle cell.”
Newborn screening helps individuals with sickle cell disease obtain early access to pediatric hematologists to discuss details of the disease and how to avoid significant pain and health complications with early management.
What are the symptoms of sickle cell disease?
Sickle cell disease symptoms often start around six months of age. Many symptoms occur because sickle-shaped cells block blood vessels, reducing circulation.
For example, symptoms can include:
- Episodes of extreme pain.
- Swelling of hands and feet.
- Frequent infections.
- Delayed growth or puberty.
- Vision problems.
Left untreated, sickle cell disease can lead to serious medical complications, including stroke, organ damage and blindness.
Is sickle cell disease genetic?
Yes, sickle cell disease is genetic, a recessive trait inherited from your parents. There are two ways a child can inherit sickle cell disease. The first is if both parents have sickle cell trait and the child inherits a copy from each parent. The second way is if one parent has the sickle cell trait, and the other parent has a different mutation to the gene that makes the hemoglobin nonfunctional or poorly functional. An example of this would be if an individual co-inherits sickle cell trait from one parent and a beta-globin mutation from the other parent.
Even if both parents have the sickle cell trait, there’s only a 25% chance the child will inherit the disease.
Dr. Ferdjallah explains, “Carrying one copy of the sickle cell mutation is very common. There are a lot of people who have the sickle cell trait, and they don’t even know that they have it or forget they have it. They don’t have symptoms.”
What is the most common treatment for sickle cell disease?
“Hydroxyurea is the single most important medication for sickle cell disease,” Dr. Ferdjallah says. “It’s on the World Health Organization’s list of essential medications. Hydroxyurea is a staple — a medication that must be taken daily and routinely.”
Hydroxyurea has an interesting history
“Hydroxyurea was originally developed to be a form of chemotherapy for leukemia,” says Dr. Ferdjallah. “But one of the things that it also does is converts a sickle cell hemoglobin into what we call ‘fetal hemoglobin’— the hemoglobin that we produced as babies inside our moms and until about 6 months of age. That type of hemoglobin does not sickle.”
She continues, “We learned about the benefits of fetal hemoglobin by studying kids with a condition called ‘hereditary persistence of fetal hemoglobin (HPFH)’ — a phenomenon where kids are born with a mutation in the beta-globin gene. They just naturally make a lot of fetal hemoglobin. Some of those kids co-inherit sickle cell disease, but they have almost no clinical symptoms of sickle cell disease. That’s because they’re producing enough fetal hemoglobin to counteract the sickling.”
Hydroxyurea treatment during the teen years
Dr. Ferdjallah says that management of sickle cell disease can get complicated in teens, as they may not be as vigilant about consistently taking their medications.
“We definitely hit a huge snag in the teenage years — it’s like clockwork. It’s also true about teenagers who have type 1 diabetes with their insulin or other chronic diseases that require daily medications. They just don’t care. It doesn’t affect them day to day, so who cares if they take their hydroxyurea? We were all teenagers and all felt invincible. I definitely get it.”
“I think the onus is on us as the medical team to reframe the purpose of hydroxyurea to these kids — to support them and meet them at their level,” she says. “Our goal is not to beat them over the head with it. It’s to show them that actually, hydroxyurea is really important, and we really do care that they stay on it.”
At Mayo Clinic, the Comprehensive Pediatric Sickle Cell Clinic has social work, nursing and psychology professionals who work with teens to find out how to motivate them to take their medication. Things like setting phone alarms to take their medication or creating posters in art therapy can be helpful.
“It’s less blame and more of a partnership, and I find that it’s a much more successful strategy,” says Dr. Ferdjallah.
Can sickle cell disease be cured?
Stem cell transplant is the only way to cure sickle cell disease. Stem cells are found in the bone marrow. The bone marrow is located inside the body’s bones and houses the blood cell factory. It’s where you find the gene mutation that causes sickle cell disease.
“A stem cell transplant is where you basically destroy the bone marrow of a patient with sickle cell disease. You empty the bone marrow and replace it with somebody else’s bone marrow,” Dr. Ferdjallah explains. “With new bone marrow, you get new stem cells that can make red blood cells that don’t sickle.”
But it’s easier said than done. There are many side effects and complications associated with a stem cell transplant, including a slight risk of death. For example, there’s a risk that the new stem cells don’t take. There’s also a real risk that the new cells attack the patient’s body organs such as skin, gut and liver.
This is why finding the right bone marrow donor is critical. There are several options to find donor bone marrow.
The most common type of donor is “a matched sibling donor” — a sibling who inherited the same genetic matching set of Human Leukocyte Antigens (HLAs) from their parents. HLAs help the immune system recognize whether a cell belongs to your body or if the body needs to get rid of it.
Dr. Ferdjallah says, with a matched sibling donor, “There’s going to be a far lower risk of the new cells attacking the recipient’s organs.”
There’s excellent data that compares patients who receive a transplant from a matched sibling to a patient who takes hydroxyurea lifelong. The odds show that patients who undergo a matched sibling transplant are significantly better off — even if you account for the risks of not surviving a transplant.
According to Dr. Ferdjallah, the main issue with sibling donors is that “you only have a one-in-four chance of being a perfect match to a sibling. So first of all, you have to have siblings and they can’t have sickle cell disease. Then, they have to be a match.”
There is an experimental approach to bone marrow transplantation where you can use a “half-match” donor — someone who shares half of the child’s genetic material, such as a biological parent.
Dr. Ferdjallah explains, “You’re always a half-match with one of your biological parents. We already use half-match donors for other diseases, such as relapsed leukemia or bone marrow failure. But we have not used it in a standardized way in sickle cell disease. So, we don’t know, with certainty, that it’s a safe or effective option.”
If your family is interested in half-match donation, Dr. Ferdjallah suggests asking your doctor about enrolling in a clinical trial.
“The final option, which is easily the most exciting, is gene therapy,” says Dr. Ferdjallah. “With gene therapy, you actually collect the patient’s stem cells which are then genetically altered to modify the gene that makes the sickle cell hemoglobin or hyper-activate the creation of fetal hemoglobin.”
“Then, stem cells get infused in your body, and the body recognizes the cells as your cells. It’s like you fixed your own genetic mutation. You don’t need foreign cells [from a donor] in your body. That completely decreases morbidity and mortality. It’s a great solution.”
Gene therapy is still in the process of becoming FDA-approved. Dr. Ferdjallah and her colleagues are anxiously awaiting the chance to bring gene therapy to patients. She says, “We’re living this innovation in real-time. So, it feels really slow to us. But we’ll probably look back and be like, ‘Wow, that was an epic boom of innovation.’ “
My Life Beyond Sickle Cell Disease
A graphic nonfiction story with a kid’s-eye view of living with, and beyond, sickle cell disease.Shop Now
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