A bone marrow transplant is a procedure to transplant healthy bone marrow into a patient whose bone marrow is not functioning properly. Problems in bone marrow are often caused by chemotherapy or radiation treatment for cancer. This procedure can also be done to correct hereditary blood diseases.

The healthy bone marrow may be taken from the patient prior to chemotherapy or radiation treatment (autograft), or it may be taken from a donor (allograft).

Bone marrow is found in a soft fatty tissue inside bones. This is where blood cells (red blood cells, platelets, and white blood cells) are produced and developed. If a patient develops a disease of the blood cells, especially cancers such as leukemia, he or she may require high doses of chemotherapy to destroy the cancer. However, this also destroys normal blood cells.

Alternatively, hereditary or acquired disorders may cause abnormal blood cell production. In these cases, transplantation of healthy bone marrow may save a patient's life. Transplanted bone marrow will restore production of white blood cells, red blood cells, and platelets.

Bone marrow transplant patients are usually treated in specialized centers and the patient stays in a special nursing unit (a bone marrow transplant unit, or BMT) to limit exposure to infections.

Donated bone marrow must match the patient's tissue type. It can be taken from the patient, a living relative (usually a brother or a sister), or from an unrelated donor (found through the national marrow donor program). Donors are matched through special blood tests called HLA tissue typing. (See HLA antigens.)

Bone marrow is taken from the donor in the operating room while the patient is unconscious and pain-free (under general anesthesia). Some of the donor's bone marrow is removed from the top of the hip bone. The bone marrow is filtered, treated, and transplanted immediately or frozen and stored for later use. Then, transplant material is transfused into the patient through a vein (IV line) and is naturally transported back into the bone cavities where it grows to replace the old bone marrow.

Alternatively, blood cell precursors, called stem cells, can be induced to move from the bone marrow to the blood stream using special medications. These stem cells can then be taken from the bloodstream through a procedure called leukapheresis.

The patient is prepared for transplantation by administering high doses of chemotherapy and/or radiation (conditioning). This serves two purposes. First, it destroys the patient's abnormal blood cells or cancer. Second, it inhibits the patient's immune response against the donor bone marrow (graft rejection).

Following conditioning, the patient is ready for bone marrow infusion. After infusion, it takes 10 to 20 days for the bone marrow to establish itself. During this time, the patient requires support with blood cell transfusions.

• Bone marrow deficiency disease caused by:
  • abnormal red blood cell production, such as thalassemia or sickle cell disease
  • aggressive cancer treatments (chemotherapy, radiation therapy), especially for leukemia or lymphoma
  • lack of normal blood cell production (aplastic anemia)
• Immune system disorders (immunodeficiency) such as:
  • congenital neutropenia
  • severe combined immunodeficiency syndrome

• Patients with heart, kidney, lungs, or liver disorders
• Patients with other diseases that may limit survival

• reactions to medications
• problems breathing

Chemotherapy given prior to bone marrow transplant (conditioning) can cause significant toxicity, such as mouth sores, diarrhea, liver damage, or lung damage. While waiting for bone marrow to grow, the patient is at high risk for infection.

The major problem with bone marrow transplants (when the marrow comes from a donor, not the patient) is graft-versus-host disease. The transplanted healthy bone marrow cells may attack the patient's cells as though they were foreign organisms. In this case, drugs to suppress the immune system must be taken, but this also decreases the body's ability to fight infections.

Bone marrow transplant prolongs the life of a patient who would otherwise die.
Relatively normal activities can be resumed as soon as the patient feels well enough and after consulting with the doctor.

Other significant problems with a bone marrow transplant are those of all major organ transplants -- finding a donor and the cost. The donor is usually a sibling with compatible tissue. The more siblings the patient has, the more chances there are of finding a compatible donor.