Bone Marrow Transplantation

What is Bone Marrow?

Bone marrow is the flexible tissue found in the interior of bones. In humans, bone marrow in large bones produces new blood cells. Bone marrow is also a vital element of the lymphatic system, as it produces lymphocytes and acts to prevent the backflow of lymph On average, bone marrow constitutes 4% of the total body mass of humans; .There are two types of bone marrow: red marrow (consisting mainly of hematopoietic tissue) and yellow marrow (consisting mainly of fat cells). Red blood cells, platelets and most white blood cells arise in red marrow. Both types of bone marrow contain numerous blood vessels and capillaries. At birth, all bone marrow is red. With age, more and more of it is converted to the yellow type; only around half of adult bone marrow is red. Red marrow is found mainly in the flat bones, such as the hip bone, breast bone, cranium, ribs, vertebrae and shoulder blades, and in the cancellous ("spongy") material at the epiphyseal ends of long bones such as the femur and humerus. Yellow marrow is found in the medullary cavity, the hollow interior of the middle portion of long bones. In cases of severe blood loss, the body can convert yellow marrow back to red marrow to increase blood cell production.

Bone Marrow Transplantation

In a bone marrow transplant, you will receive healthy stem cells after your own bone marrow has been destroyed. Bone marrow or stem cell transplant may be recommended for:

1. Certain cancers, such as leukemia, lymphoma, and multiple myeloma

2. Illnesses where the bone marrow does not produce the right kind of or enough cells. Some of these are:

i. Sickle cell anemia

ii. Aplastic anemia

iii. Thalassemia

iv. Congenital neutropenia

v. Severe immunodeficiency syndromes

vi. Rescue transplant to replace bone marrow, when treatment for cancer has destroyed a patient’s bone marrow. There are three kinds of bone marrow transplants:

Autologous bone marrow transplant : "Auto" means "self." Stem cells are taken from the patient before the patient gets chemotherapy or radiation treatment. When chemotherapy or radiation is done, the patient gets their stem cells back. This is called a "rescue" transplant. It allows the patient to receive high doses of chemotherapy and radiation.

Allogeneic bone marrow transplant: "Allo" means "other." Stem cells come from another person, who is called a donor. Donor stem cells come from the donor’s bone marrow or their blood. Most times, a donor must have the same genetic typing as the patient, so that their blood "matches" the patient’s. Special blood tests will tell whether a possible donor is a good match for the patient. A patient’s brothers and sisters have the highest chance of being a good match (25% chance for each full sibling), but sometimes parents and children of the patient and other relatives may be matches. Donors who are not related to the patient may be found through national bone marrow registries.

Umbilical cord blood transplant: Stem cells are taken from an umbilical cord right after delivery of an infant. The stem cells are tested, typed, counted, and frozen until they are needed for a transplant. Umbilical cord blood requires less stringent matching because the stems cells are so immature.

Factors That Count

Parameters that define success rate include

1. What disease you have

2. What type of treatment (eg. chemotherapy, radiation) you have before the bone marrow transplant

3. How old you are

4. How healthy you are when you have your transplant

5. How good a match your donor is

6. What type of bone marrow transplant patient you are having (autologous, allogeneic, or umbilical cord blood)

Possible Complications

Complications you may have are:

1. Infections: These may be very serious.

Bleeding: This can happen in the lungs, the intestines, brain, and any other part of the body.

2. Anemia

3. Diarrhea, nausea, and vomiting

4. Pain

5. Severe mucositis (inflammation and soreness) in the mouth, throat, esophagus, and stomach

6. Damage to the kidneys, liver, lungs, and heart

7. Cataracts

8. Early menopause

9. Graft failure, which means that the new cells do not settle into the body and start producing stem cells

10. Graft-versus-host disease: This is when your donor’s cells attack your own body. In the first few months after the transplant, symptoms may be a skin rash, diarrhea, or abnormal liver tests. Later, symptoms may be dry eyes or mouth, tightness of the skin, scarring in the lungs, chronic diarrhea, and other problems.

11. Children who get transplants may have delayed growth.

BMT for Thalassemia

The only curative treatment for thalassaemia is allogeneic stem cell transplantation if there is a HLA identical sibling or family member. Mother, father and first degree relatives could be matched, especially if the parents are related, and it might be worthwhile evaluating by HLA typing. If done between the ages 2-7 years, the success rate for this procedure is 80 -90%. The cost of the transplant which is approximately Rs 8-10 lakhs per patient is equivalent to looking after a thalassaemia major patient for 5-8 years with supportive care. On average a BMT requires a hospital stay of 1.5 to 2 months. Most children become transfusion-independent within a month from the transplant. Late rejections and transplant-related complications, however, may occur and regular check up should be carried out at least for the first year following the BMT. Other options like transplantation from unrelated marrow donor registries, cord blood banks or from a partially matched family member (generally the mother) have been performed successfully but are currently quite expensive and risky. Transplantation form unrelated donors (bone marrow or cord blood) in Thalassemia generally requires extended compatibility and thus the chances of finding a suitable unrelated donor are not very high especially if the ethnic background is underrepresented in bone marrow. Transplant from mother (called Haploidentical Transplant), currently has a success rate in the range of 50% and a 20% mortality risk, these results, however, may improve with time Generally there is no risk to donor even if he/she is Thalassemia minor and bone marrow collected from him/her is replaced by their body without any pain. Bone marrow from donor is collected under general anesthesia from upper part of hip bone. For related bone marrow donation (generally from a brother or a sister) there is really no age limit, a bone marrow harvest can be safely performed between 6 months and 60, years of age if the donor is in good health. It is only for unrelated (donor registries) bone marrow donation that the age limit is much narrower, generally between age 20 and 40.

References:

1. https://www.wikipedia.org/

2. http://www.cure2children.org/

3. http://www.nlm.nih.gov/medlineplus/ency/article/003009.htm