Why do minority patients have a much harder time finding a match for bone marrow transplants?
It’s not easy to look for a specific boy among hundreds of first graders, especially when they swarm into lines for cupcakes and cotton candy. On this fall bake-sale day, the cafeteria of Public School 106 in the Parkchester section of the Bronx is buzzing with energy and children’s happy shrieks. A few teachers shout across the hall to keep things from spinning out of control. And when I finally spot 6-year-old Asaya Bullock, he seems to be well in hand.
“Ready for your green soup?” Charline, his mother, takes out a thermos with a Spider-Man design on the side.
The green soup is one of the only three things Asaya has ever been able to eat. He drinks it for breakfast, for lunch, for dinner; he drank it for the whole trip that his family took to the Caribbean to visit his mom’s relatives. Luckily, with broccoli, kale, green beans, and some minced meat, Asaya’s soup is at least healthy — and better than the small bowl of potato chips used as comfort food after his bi-weekly belly infusion. The recurring medical procedure helps keep him alive.
The boy takes the thermos and nods silently. His big bright eyes briefly meet mine, although I am a total stranger and the only Asian in this Hispanic and African-American school. Asaya is a bit shy before he launches into his plan to buy another pair of shoes with his pocket money, and then once he starts to talk, he forgets to finish his soup. His slim build and patchy thin hair make me wonder if he feels cold on this chilly October afternoon.
Asaya used to wear his hair in cornrows. But it was too hard to maintain once he got sick again from his rare autoimmune disease. Charline insists on sending him to school, arranging doctors’ appointments only on days without many classes. “Every day counts in first grade,” she told me when we first talked on the phone.
Charline sounds very much like a normal parent, except she’s constantly on the search, desperately looking for something she has one-in-a-billion odds of finding: a life-saving match for Asaya’s bone marrow.
Asaya has been fighting IPEX syndrome since even before he was officially diagnosed at 20 months old. Living with this rare autoimmune disease means the immune system constantly attacks and destroys the body’s own tissues, especially certain intestinal cells. Patients hardly ever live beyond their twenties. And his best bet for a cure is a bone marrow transplant.
Finding matching bone marrow is always hard. The human immune system uses unique cellular tags to distinguish the “self” of one’s own tissues from invading foreign cells. Called human leukocyte antigens (HLAs), these markers are critical to bone marrow transplant success. Transplanting bone marrow with mismatched HLAs will not cure but kill.
What makes Asaya’s situation even trickier is his ethnicity. Because HLAs are inherited, people in need of donations must usually look to others who share their ethnicity and ancestry. But there are far fewer black people in donor registries than white people. According to the donor-matching assistance organization Be the Match, 8.7 million of its adult donors are white and only 845,000 are black.
Organizations and researchers are working hard to study why this disparity exists, and to increase donor diversity. While alternative approaches to getting or creating suitable cells for a transplant like umbilical cord blood and gene editing therapy do exist or are under development, for boys like Asaya, finding a bone marrow match is still where the greatest hope lies.
The question is, what can be done to make that hope more realistic?
Invisible Inequalities
In a bone marrow search, most people try their families first. But 70% end up looking for a match among strangers.
Because there are fewer minority donors in the registry, it’s harder for minority patients to find a match. According to Be the Match, black people have a 66% likelihood of finding a matched, available donor in the registry. It’s 97% for white people.
These numbers have real consequences. A 2015 research paper in Bone Marrow Transplantation discovered that black people experience a “longer time from diagnosis to transplant,” and they are “more likely to have an HLA-mismatched donor …compared with whites.”
As scientists have repeatedly pointed out, the concept of race is fundamentally cultural, not biological. Nevertheless, because some realities of population genetics are unfortunately caught up in the false rhetoric of race, we might have to rely on the construct and acknowledge the biological differences in HLAs in order to save lives.
Black people already have a highly mixed genetic heritage because of the history of involuntary migrations across the world imposed by slavery and colonialism. “As those mixes take place it creates a more complicated HLA type,” much rarer than that of somebody who comes from a single ethnic heritage, says Galen Switzer, a University of Pittsburgh School of Medicine professor. Such diversity in HLA types makes it more difficult even for any two black people to match.
Rethinking Roadblocks
Expanding minorities’ populations in the registry is an obvious solution. But that’s easier said than done. It had been known that ethnic minority groups have lower rates of proceeding to the actual donation than whites. Switzer and his colleagues set out to understand why.
Religious objection seems to play a role. In a 2012 survey participants were asked a series of questions like “Do you believe that your religion might be opposed to bone marrow donation?” Switzer found that white people were less likely than other groups to say religion was important in their lives (a claim largely supported by this Pew survey on religion in America), and less likely to say their religion would keep them from becoming a donor.
Distrust of the medical system is another major issue. Compared with white people, the study has found, black people and other minority groups tend to agree more with statements like “People can get access to my medical records without my approval.” They had even more distrust than white people did when researchers asked whether they think their bone marrow donation would be allocated fairly. Considering black people, Native Americans, and other marginalized populations in America have a history of being experimented on without their knowledge or consent, it’s entirely understandable why there is still suspicion regarding the motives of the medical community.
However, according to the survey, “The most consistent factor associated with opting out of the registry across all race/ethnic groups was ambivalence about donation: doubts and worries, feeling unsure about donation, wishing someone else would donate in one’s place.”
Organizations like Be the Match and the Icla da Silva Foundation have been tackling these issues for years. For example, the Foundation deploys staff from the same background of donor targets to talk to people and help arrange doctor checkups after the donation. Now, among their 38,000 new donors per year, 90% are from non-white backgrounds.
The black community is still the hardest to reach, says Mary Halet, director of community engagement at Be the Match. Halet and colleagues have recently launched a campaign featuring Mike Conley of the Memphis Grizzlies speaking about bone marrow transplant as a cure for sickle cell disease. As many black people know individuals who are impacted by sickle cell disease, Halet says, “it cut through the clutter and people tune in.”
Alternative Paths
For patients like Asaya, umbilical cord blood that also contains stem cells with the power of transplanting a whole new immune system could be another source of hope, as it doesn’t have to be as closely matched as adult bone marrow.
Umbilical cord blood is harvested from newborns’ umbilical cord. Newborns have a naïve immune system that hasn’t been challenged by vaccines or infections, and their cord blood won’t react as strongly against a transplant recipient.
But most physicians consider cord blood transplant as a “second line” treatment, mainly because of the limited volume — as little as 100 ml per umbilical cord — and limited numbers of stem cells available.
Even with matched cord blood, things could go wrong. Asaya’s parents, Charline and Vincent Bullock, gave birth to their daughter Anaya not long after learning about Asaya’s diagnosis. But although Anaya’s cord blood is a 70% match, her donation did not cure her brother. “In 20 days his body started rejection,” Charline remembers. “We spent every week in the hospital.”
That’s why gene editing therapy research is gaining so much momentum — to see if a patient can do without another person’s tissue. The idea is to take out the patient’s own bone marrow stem cells, correct them in lab, and then return the healthy cells back into the body.
In this way, we might arrive at a day when race categorization finally does not matter for treatment anymore.
Hope exists for Asaya’s IPEX syndrome. Dr. Tory Torgerson, an IPEX expert at Seattle Children’s Hospital who’s been in touch with the Bullock family since Asaya’s diagnosis, has used CRISPR gene editing tools to correct the disease-causing gene in cells and mouse models. He says in three years they would be ready for patients. Before then he hopes Asaya finds a match soon and the immuno-suppression drugs will keep working.
We might arrive at a day when race categorization finally does not matter for treatment anymore. Click To TweetOn the day of my visit, Asaya received his bi-weekly belly infusion of immunosuppression drugs at home. By avoiding traveling to the hospital, the family saves a lot of time and reduces the risk of infection. Charline told me their doctor had asked them to videotape a session. She wanted to use it to encourage other patients. So I assumed the procedure wouldn’t be a big deal.
But I was wrong.
First, during my visit, the numbing cream didn’t seem to work. After the first needle went in — with Asaya already crying and begging — Charline had to pierce two additional needles through her little boy’s upper stomach skin.
If there is a bright side to any of this, it’s that they go through everything as a family. Vincent, a mellow, quiet man, hovers over his son, whispering a story in which Asaya rides along an exciting mountain trail, to take his son’s mind off the third approaching needle. Anaya is also distressed after seeing the infusion procedure, so Charline comforts the 3-year-old by building her a tent in the living room of their Bronx apartment. “Don’t break it! You! I’ve had it since I was 14,” jokes Charline, as the little girl creates a hexagonal tent base instead of a square.
As more plastic sticks and ball-shaped joints fall into place, the tent rises from 2D to 3D. It seems perfect for hiding from all the worries in the world.
It’s just that Anaya disagrees with Charline again. “We don’t need a door,” she announces.
“No, we are gonna build something on the door and roll it up.”
“How do we do it?” asks the little girl.
Charline doesn’t stop pulling another sheet on top of the tent’s skeleton to make it more comfortable. “We’ll figure it out,” she says. “We always figure it out.”
