Bone Marrow

A bone marrow transplant is when special cells (called stem cells) that are normally found in the bone marrow are taken out, filtered, and given back either to the same person or to another person.

A bone marrow transplant is when special cells (called stem cells) that are normally found in the bone marrow are taken out, filtered, and given back either to the same person or to another person.

Why Is It Done?

Bone marrow produces stem cells. These stem cells eventually develop into blood cells. Bone marrow is a critical part of the body because it is the body's main blood cell "factory." If something is wrong with the marrow, a person can become very ill, even die.

In diseases such as leukemia and aplastic anemia, the bone marrow is unhealthy. The purpose of a bone marrow transplant is to put healthy stem cells in place of the unhealthy ones. This can treat or even cure the disease.

Two Types of Bone Marrow Transplants

• Autologous bone marrow transplant - The donor is the person him/herself.
• Allogenic bone marrow transplant - The donor is another person whose tissue has the same genetic type as the person needing the transplant (recipient). Because tissue types are inherited, similar to hair or eye color, it is more likely that the recipient will find a suitable donor in a brother or sister. This, however, happens only 25 to 30 percent of the time.
  
  If a family member does not match the recipient, the National Marrow Donor Program Registry database is searched for an unrelated individual whose tissue type is a close match. It is more likely that a donor who comes from the same racial or ethnic group as the recipient will have the same tissue traits. The chances of a minority person in the United States finding a registry match are lower than that of a white person (see article, Marrow Matches For Minorities Are Harder to Find).

Sources of Bone Marrow Stem Cells

• Bone marrow harvest: Collecting stem cells by taking them directly out of the bone.
• Apheresis: Collecting stem cells by filtering the blood for peripheral (circulating) blood cells (PBSC).
• Umbilical cord blood: Stem cells are filtered from blood in the umbilical cord after a baby is born.

The majority of marrow stem cell transplants are made using PBSC collected by apheresis, since this method has better results for both the donor and the recipient.

What the Donor Experiences

In most cases, a donation is made using circulating stem cells (PBSC) collected by apheresis. First, the donor receives injections for a few days of a medication that causes stem cells to move out of the bone marrow and into the blood. For the stem cell collection, the donor is connected to a machine by a needle inserted in the vein (like for blood donation). Blood is taken from the vein, filtered by the machine to collect the stem cells, then returned back to the donor through a needle in the other arm. There is almost no need for a recovery time with this procedure.

If stem cells are collected by bone marrow harvest (much less likely), the donor will go to the operating room and while asleep under anesthesia, a needle will be inserted into either the hip or the breastbone to take out some bone marrow. After awakening, he/she may feel some pain where the needle was inserted.

What the Recipient Experiences

Bone marrow transplant is a difficult procedure to go through. Usually the person receives high doses of chemotherapy and/or radiation to eliminate whatever bone marrow he/she has left and make room for the new marrow transplant. Once this is done, the new stem cells are put into the person intravenously, like a blood transfusion. The stem cells will then find their way to the bone and start to grow and produce more cells (called engraftment).

Serious problems can occur during the time that the bone marrow is gone or very low. Infections are common, as is anemia, and low platelets in the blood can cause dangerous bleeding internally. Recipients often receive blood transfusions to treat these problems while they are waiting for the new stem cells to start growing.