What is a Bone Marrow Match?

A bone marrow match occurs when a bone marrow donor has marrow that matches with someone in need of a bone marrow transplant. People who are diagnosed with serious immune system, blood or genetic diseases may choose to undergo a bone marrow transplant as one of their treatment options. A bone marrow transplant replaces unhealthy cells that form blood with healthy ones from a donor. Once a person has decided to proceed with a transplant, he or she must find a donor with a successful bone marrow match.

When a donor and patient’s bone marrow compatibility is tested, doctors are looking for matching HLA tissue types. HLA stands for human leukocyte antigen, which is a hereditary protein found on most of the cells in the body. These proteins act as markers and signify which cells belong in the body and which do not. Because these markers are hereditary, each person has two sets which include one from each parent.

To evaluate a person’s bone marrow, doctors look at six HLA antigens, but many transplant centers look at eight or ten antigens. For a successful bone marrow match, at least five antigens must match. The process used to ensure the best match possible for a donor and recipient is called confirmatory typing. Bone marrow transplants that use the marrow of another person are called an allogenic bone marrow transplant and are the most popular.

Because HLA tissues are genetic, most doctors first look for donors within the family, with the best chance of matching a sibling. It is important to note that not all people with siblings will have a successful match. According to the National Marrow Donor Program, only 30 percent of bone marrow recipients will find a successful match within their family. In the event that a match within the family cannot be found, doctors check the national bone marrow registry. Finding a successful bone marrow match on the registry is purely luck. Sometimes there is an immediate match and sometimes recipients must wait weeks or months before a match is found.

It is a common misconception that donating bone marrow is a painful procedure. A blood marrow donor who has been matched with a recipient must undergo surgery. Donors are given anesthesia and hollow needles are used to draw liquid marrow from the back of the pelvis. There will be mild soreness in the lower back for a few days. Most donors return to normal daily activities within a few days and can expect their bone marrow to be completely regenerated within four to six weeks.