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barbara
06-22-2009, 03:54 PM
Medical Edge: Bone marrow donation involves a less-invasive technique
6/22/2009


DEAR MAYO CLINIC: What's involved in becoming a bone marrow donor?

A person can become a bone marrow donor in two ways. One is to donate to someone you know, usually a family member, who needs a bone marrow transplant. The second is to have your name listed on a national registry of willing bone marrow donors. This registry is used when people who need a bone marrow transplant cannot find a relative who is a compatible donor. Bone marrow donation previously involved a minor surgical procedure, but a less-invasive technique is now used most often.

Although the procedure is called a bone marrow transplant, it is actually the blood-forming (hematopoietic) stem cells within bone marrow that benefit the transplant recipient. Bone marrow stem cells can develop into red blood cells that carry oxygen to the body, platelets that help blood clot, or white blood cells to help fight infection.

People who need a bone marrow transplant often have blood disorders such as leukemia, lymphoma or severe anemia. A bone marrow stem cell transplant may be necessary for people with one of these conditions because of two reasons. Their bone marrow may not be able to produce enough healthy blood cells, or their marrow may not be able to re-grow sufficiently following chemotherapy or radiation therapy. A bone marrow stem cell transplant can help regenerate the blood cells their bodies need, reducing the risk of life-threatening infections, anemia and bleeding.

Preferably, people who need a bone marrow transplant should receive their own stem cells, if possible. This process, called autologous transplant, is safer for the recipient. But, in some cases, a person's bone marrow may be too diseased for transplantation. In those situations, stem cells from a donor (allogeneic transplant) must be used.

To be a bone marrow donor, you must have stem cells in your bone marrow that match the recipient's. To determine if you're a match, doctors use a test called human leukocyte antigen typing. This test compares the characteristics of stem cells in your bone marrow to those of the potential recipient, to determine the similarity of cell proteins. A close match increases the chances that the recipient's body will accept the new stem cells. Doctors test stem cell types by examining a small sample of blood or a swab of tissue from inside the cheek.

If you are accepted as a donor, a procedure is performed to gather your stem cells. In the past, that involved minor surgery to draw approximately 1 to 1.5 quarts of bone marrow from your hip bones. Stems cells were collected from the donated marrow. Now, that process is used less frequently.

Today, blood-forming stem cells are more often collected by filtering them directly from your bloodstream. Prior to that procedure, you're given a daily medication for five days to stimulate production of stem cells, so more of them are circulating in the bloodstream, and they can be easily separated from the rest of the blood.

On the fifth day, the stem cells are collected using a process called apheresis. Blood is drawn from a vein in the arm and sent through a machine that separates out the blood-forming stem cells.

After separation, your blood is returned to you through a vein in the other arm. Apheresis takes about four to six hours. Typically, you undergo two to four apheresis sessions, depending on how many stem cells are needed, and if you are donating to yourself or to someone else.

After your donation, the recipient receives the stem cells through a process that's similar to a blood transfusion.

The donated stem cells are infused into the recipient's body over a period of about one to five hours. The transplanted stem cells make their way to the recipient's bone marrow cavities, where they begin creating new bone marrow and stem cells.

Bone marrow donors are always needed. The National Marrow Donor Program maintains a registry of potential donors from across the United States. You can find more information at the program's Web site at www.marrow.org. -- Dennis Gastineau, M.D., Hematology, Mayo Clinic, Rochester.