Bone marrow transplant Health Article

Definition

A bone marrow transplant is a procedure that transplant healthy bone marrow into a patient whose bone marrow is not working properly. A bone marrow transplant may be done for several conditions including hereditary blood diseases, hereditary metabolic diseases, hereditary immune deficiencies, and various forms of cancer.

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).

Alternative Names

Transplant - bone marrow

Description

Bone marrow is a soft, fatty tissue inside the bones. This is where blood cells (red blood cells, platelets, and white blood cells) are produced, and where they develop. In a disease of the blood cells -- especially cancers such as leukemia -- high doses of chemotherapy may be required to destroy the cancer. However, this also destroys normal blood cells.

In other cases in which hereditary or acquired disorders cause abnormal blood cell production, transplantation of healthy bone marrow may correct these problems. 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. 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 donor 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. Transplant marrow is transfused into the patient through a vein (IV) and is naturally carried into the bone cavities where it grows to replace the old bone marrow.

Alternatively, blood cell precursors, called stem cells, can be made 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 transplant by administering high doses of chemotherapy or radiation (conditioning). This serves 2 purposes. First, it destroys the patient's abnormal blood cells or cancer. Second, it slows 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 - 20 days for the bone marrow to establish itself. During this time, the patient requires support with blood cell transfusions.

Indications

Bone marrow transplant may be recommended for:

• 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 (immunodeficiencies) such as:
  • Congenital neutropenia
  • Severe combined immunodeficiency syndrome
• Specific forms of cancer:
  • Leukemias
  • Lymphomas
  • Myeloma

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

Risks

The risks for any anesthesia are:

• Reactions to medications
• Problems breathing

Chemotherapy given prior to bone marrow transplant (conditioning) may 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.

Expectations after surgery

Ideally, bone marrow transplant lengthens 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 -- the finding of a donor, and the cost. The donor is frequently a sibling with matching tissue. The more siblings the patient has, the more chances there are of finding a matching donor.