When someone needs a stem cell transplant, doctors usually look for a very close match. That match might come from a brother or sister or from an unrelated stem cell donor on the registry.
But that doesn’t always happen.
A haploidentical stem cell transplant, often just called a haplo, gives people another option when doctors can’t find a fully matched donor.
Haplo transplants have changed what’s possible for many people facing blood cancer and other serious blood disorders.
What haploidentical actually means
Haploidentical sounds complicated, but the idea’s simple. It means half-matched.
When someone needs a stem cell transplant, doctors look at tissue type. Tissue type’s determined by proteins on the surface of cells called HLA markers. These markers help the immune system recognise what belongs in the body and what doesn’t. They’re inherited from your mum and dad, with half coming from each parent.
Doctors aim for the closest match possible. A fully matched brother or sister’s often the first choice. If that’s not available, doctors may look for a closely matched unrelated stem cell donor through the stem cell donor registry.
But that’s not always possible.
A haploidentical stem cell transplant uses a half-matched parent, child, brother, or sister as the donor.
Haplo transplants turn a family connection into a real treatment option when a full match can’t be found.
For more detail on how haplo works and why it’s used, this explanation from Anthony Nolan is helpful.
Why donor matching matters in stem cell transplants
Finding donors with the closest tissue type matters because a stem cell transplant isn’t just about replacing blood cells. It’s about introducing a whole new immune system into someone’s body.
Those donated stem cells grow into new blood and immune cells. If the match isn’t close enough, the new immune system can see the patient’s body as foreign and start attacking it. Doctors refer to this reaction as graft vs host disease, or GvHD.
Doctors aim for the closest match they can find. A strong match can mean fewer complications, a smoother recovery, and better long-term outcomes.
When doctors can’t find a fully matched donor, haplo transplants give them another solid option without closing the door on safety or success.
How haploidentical transplants became possible
For a long time, doctors avoided using half matched donors. The risk of serious complications was simply too high.
The biggest concern was how strongly the new immune system might react inside the patient’s body. When donor cells and patient tissue were too different, the chances of severe GvHD increased.
Over time, research changed that.
Doctors developed better ways to manage the immune response after transplant. This included improved medications, more precise treatment plans, and closer monitoring during recovery.
These advances made it possible to use half matched donors more safely. Outcomes improved, and survival rates began to look much closer to those seen with fully matched stem cell transplants.
Abbey donated her stem cells to her mum when she needed a transplant.
Abbey donated her stem cells to her mum when she needed another transplant. You can read Abbey’s story here.
Haplo transplants are now a well-established option in modern transplant care, supported by years of research and clinical experience.
When doctors use a related stem cell donor
Doctors consider a related stem cell donor when they can’t find a fully matched donor or when time matters.
Some people need a stem cell transplant urgently. Waiting months for a suitable unrelated donor isn’t always an option. In these cases, a related donor can make treatment possible sooner.
Doctors may also use a related donor when someone’s tissue type makes it harder to find a close match on the stem cell donor registry.
Using a related donor doesn’t mean lowering standards. Doctors still assess donors carefully and choose the safest option for each patient.
Why haplo transplants are becoming more common
One key reason haplo transplants are being used more often is because tissue type is closely linked to ethnic background.
People from diverse or mixed ethnic backgrounds often find it much harder to find a closely matched stem cell donor. Tissue type’s inherited, so matches are more likely to be found within the same ethnic background or mix of backgrounds. When registries don’t reflect that diversity, people can wait longer for a match or never find one at all.
In these situations, doctors can’t always wait for a matched unrelated donor to be found. Looking within families for a half-matched parent, child, brother, or sister can make a transplant possible.
For some people, haplo transplants mean hope when the usual options aren’t there. They give families another chance to step in and help make life saving treatment possible.
Why we still need the stem cell donor registry
Even with haplo transplants, the stem cell donor registry still matters a lot.
Not everyone has a brother or sister who can donate. Some people are only children. Some are estranged from family. In other cases, parents may be too old or aren’t medically able to donate.
For many people, a family donor simply isn’t an option.
That’s where the stem cell donor registry becomes critical. It connects patients with unrelated stem cell donors who share a close tissue type match, even if they live on the other side of the world.
The more people who join the registry, especially young people from diverse backgrounds, the better the chances are that someone will find the match they need in time.
Haplo transplants expand what’s possible, but they don’t replace the need for a strong and diverse registry. Both matter, and both save lives.
If you’re aged 18 to 35, you can sign up to be a stem cell donor with just a few simple cheek swabs.
Be a legend, save a life.
References
National Marrow Donor Program – Haploidentical Stem Cell Transplants
Anthony Nolan – Haploidentical Stem Cell Transplants