To understand what a bone marrow transplant is, you must start from the beginning. What is bone marrow? Bone marrow is the spongy tissue found inside bones. The bone marrow that is located inside the breastbone, skull, hips, ribs, and spine contain stem cells that produce the body's blood cells. These blood cells include white blood cells (leukocytes) that fight off infections found in the body, red blood cells (erythrocytes) which carry oxygen to the various parts of the body and deliver the waste products from the organs and tissues. These bones also make platelets, which enable the blood to clot, preventing hemophilia and extreme blood loss.
In patients with leukemia, anemia, and some immune deficiency diseases, the stem cells in the bones' marrow are malfunctioning, producing a defective or immature blood loss or low blood cell count. Leukemia occurs when the leukocytes aren't fully matured, making the body unable to fight off infection. Anemia is when there is a low blood count, which makes the body unable to fight infections efficiently without exhaustion. These immature or defective blood cells interfere with the production of the normal blood cells that accumulate in the blood stream and may invade other tissues.
Bone marrow transplantation is a rather new medical procedure that is being used to treat a disease that used to be incurable. It was first successful in 1968 and has been used to treat patients diagnosed with leukemia, anemia, lymphomas such as Hodgkin's disease, multiple myeloma, immune deficiency disorders, and even some solid tumors such as breast and ovarian cancers.
7,500 people underwent bone marrow transplantation in 1991. Although this process now saves thousands of lives each year, over 70% of those needing a bone marrow transplant can't get one because they are unable to find a suitable donor.
In a bone marrow transplant, the patient's diseased bone marrow is destroyed and healthy marrow (taken from a healthy individual whose marrow is a close genetic match, usually a relative) is infused into the patient's blood-stream. In a successful transplant, the new bone marrow migrates to the cavities of the large bones, engrafts and begins producing normal blood cells.
If a bone marrow donor is found, the transplant is called an “allogeneic” bone marrow transplant or a “syngeneic” bone marrow transplant if the donor is an identical twin. In an allogeneic BMT the new bone marrow infused into the patient must match the genetic makeup of the patient's own marrow as closely as possible. Certain blood tests are conducted to decide whether the bone marrows match up or not. If it is not a good match, the patient's body will recognize it as foreign material, and begin to attack and destroy it. This can be very dangerous. There is a 35% chance that the patient will have a sibling whose bone marrow is a perfect match. If the patient has no sibling match, the donor may be located in a donor registry. In some cases, patients may be their own bone marrow donor. This is called an “autologous” BMT and it is possible if the condition being treated doesn't involve the bone marrow (i.e. breast cancer, ovarian cancer, Hodgkin's disease). The bone marrow is extracted from the patient before the transplant and may remove the lingering malignant tumors.
A bone marrow transplant, like any other surgery, can be very difficult and dangerous but also very effective and beneficial, saving thousands of lives every year.
By Jessica Maughan