Bone marrow is the soft, spongy tissue found inside the bones. It is where most of the body's blood cells develop and are stored. The blood cells that make other blood cells are called stem cells. The most primitive of the stem cells is called the pluripotent stem cell. This is different than other blood cells concerning the following properties:

• Renewal; it can reproduce another cell identical to itself.

• Differentiation; it can generate one or more subsets of more mature cells.

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The goal of a bone marrow transplant is to cure many diseases and types of cancer. If the doses of chemotherapy or radiation required to cure cancer are too high for treatment to permanently damage or destroy a person's bone marrow stem cells, a bone marrow transplant may be needed. Bone marrow transplants may also be needed if the bone marrow has been destroyed by the disease.

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 A bone marrow transplant can be used to:

• Replace diseased, nonfunctioning bone marrow with healthy functioning bone marrow (for conditions such as leukemia, aplastic anemia, and sickle cell anemia).

• Regenerate a new immune system that will fight existing or residual leukemia or other cancers not killed by the chemotherapy or radiation used in the transplant.

• Replace the bone marrow and restore its normal function after high doses of chemotherapy and/or radiation are given to treat a malignancy. This process is often called rescue.

• Replace bone marrow with genetically healthy functioning bone marrow to prevent more damage from a genetic disease process (such as Hurler's syndrome and adrenoleukodystrophy).

There are 4 ways to have a bone marrow transplant:

• Autologous transplant: Transplantation of the recipient's stem cells.

• Allogeneic transplant: Fully compatible stem cell transplant from someone else, regardless of whether the recipient is a relative or not.

• Haploidentical transplantation: Transplantation of first-degree relatives of the recipient between semi-compatible tissues.

• Syngeneic transplant: Transplantation of stem cells from an identical twin to the recipient.

The risks and benefits must be weighed in a thorough discussion with your healthcare provider and specialists in bone marrow transplants before the procedure.