Bone marrow is a sponge-like tissue that runs through the hollow interior of bones. The bone marrow is where the components of blood are produced: erythrocytes (red blood cells), leucocytes (white blood cells) and platelets. The erythrocytes carry oxygen from the lungs to the rest of the organism while bringing back carbon dioxide to be expelled through respiration. The leucocytes are the fundamental building blocks of the immune system, fighting against infection. Platelets serve an important function in coagulating blood.

Bone marrow transplant (BMT) is recommended in the treatment of diseases that affect proper bone marrow functioning, such as hematological conditions, immunodeficiency, some genetic illnesses, auto-immune diseases and certain cases of tumors in solid organs.
There are two types of transplant: autologous, in which the marrow and stem cells are taken from the individual him/herself, and allogenic, in which the material is supplied by a donor.

How the transplant works

After undergoing chemotherapy to destroy the remaining marrow, the patient receives new marrow via a process akin to blood transfusion. This new marrow is rich in stem cells that circulate through the bloodstream until eventually deposited in the bone, where they differentiate into other cell types. During this initial period the patient is susceptible to infections, including fungal infections, as the immune system is severely weakened. For this reason, the recipient is kept in isolation for a period of 2 to 4 weeks.

The donor faces few risks and these are largely determined by whether or not a general anesthetic is required for extraction. Only a small amount of marrow is needed and this is extracted by needle insertion into the hipbone. The bone marrow of the donor is usually completely replenished within a matter of weeks.

The importance of donation

Bone marrow transplant requires a high degree of compatibility between the donor and recipient. It is estimated that the chances of compatibility between siblings is in the region of 35%. When a donor is sought outside the recipient’s family, the chances of compatibility diminish significantly, and the ethnic mix so typical of the Brazilian population further exacerbates the problem. This is why it is so important that Bone Marrow Donor and Search Centers have an extensive list of registered donors, as this is the only way to maximize the chances of finding a suitable match.

Links

Sociedade Brasileira de TMO: www.sbtmo.org.br
Como se tornar um doador de medula óssea: www.inca.gov.br
Associação de Medula Óssea: www.ameo.org.br