A haploidentical transplant is a type of allogeneic transplant. It uses healthy, blood-forming stem cells from a half- matched donor to replace the unhealthy ones. The donor is typically a family member.

For allogeneic transplants, your doctor tests your blood to find out your human leukocyte antigen (HLA) type. HLA is a protein — or marker — found on most cells in your body. Doctors look for a donor or umbilical cord blood that closely matches your HLA.

But sometimes they can’t find a close HLA match. Then, a haploidentical transplant may be an option. This is a type of allogeneic transplant where the donor matches exactly half of your HLA.

A haploidentical, or half-matched, donor is usually your mom, your dad or your child. Parents are always a half-match for their children. Siblings (brothers or sisters) have a 50% (1 out of 2) chance of being a half-match for each other. It’s very unlikely that other family members (like cousins, aunts or uncles) would be a half-match.