In recent years, bone marrow transplants, peripheral blood stem cell transplants and cord blood transplants have become mainstream treatments for patients with certain life-threatening blood, genetic or immune system disorders.

They offer hope of remission or cure for people with diseases such as leukemia, lymphoma, multiple myeloma,severe aplastic anemia, severe combined immunodeficiency,Wiskott-Aldrich syndrome, thalassemia major and sickle cell disease.

All these diseases have one thing in common: either the disease or the treatment for the disease causes problems with the cells in the blood.

There are three types of blood cells:

• White blood cells, which fight infection.

• Red blood cells, which transport oxygen from the lungs to the rest of the body.

• Platelets, which help blood clot and stop bleeding after an injury.

Without the right number of good-quality blood cells of all three types, the body is left vulnerable to infection, anemia and bleeding problems.

With leukemia, lymphoma and some other cancers, treatment with chemotherapy and/or radiation therapy wipes out cancerous cells, but also kills stem cells in the bone marrow. Bone marrow is the soft, fatty substance in the middle of our bones, where blood cells are formed by stem cells.

People who need new, healthy blood-forming stem cells can get transplants from three sources: bone marrow, peripheral blood stem cells or cord blood. Sometimes, an autologous bone marrow donation is possible, meaning a patient's bone marrow is collected before he or she undergoes chemotherapy or radiation therapy. Then, after the treatment wipes out the remaining bone marrow, the stem cells from the previously collected marrow are given back to the patient through an intravenous line.

However, autologous transplants are not always possible. Often, transplants must come from a donor. About 30 percent of patients have a family member with a matching tissue type who can donate. The other 70 percent of patients without a donor in the family must hope that a suitable match can be found in the National Marrow Donor Program (NMDP) registry.

The NMDP has more than 5.5 million potential donors. The donor and recipient must have matching tissue types, or else the recipient's body will reject the transplanted cells. Another option is cord blood; there are more than 40,000 units of cord blood in the NMDP registry.

Here is an overview of the three types of transplants:

• Bone marrow transplantation means that a donor must have some bone marrow removed from the pelvic bones with a needle. General or regional anesthetic is usually given to minimize discomfort. The bone marrow, containing normal stem cells, is processed and can be frozen for later transplantation.

• Peripheral blood stem cell transplants require the donor to donate blood (much like giving blood for blood transfusions). For a few days before donation, the donor takes medication to increase the number of stem cells circulating in the blood. Stem cells in the blood are removed and frozen for future transplantation; the rest of the bloodcells are immediately returned to the donor.

• Cord blood transplants use the stem cells found in the umbilical cord of newborn babies. After a baby is born and the umbilical cord is cut, blood from the cord can be processed and frozen for future use.

This is only done with permission from the mother, and poses no risks for the baby. Since there is only a small amount of cord blood, cord blood transplants are usually given to children or small adults.

Recipients are given one of these types of transplants intravenously.

The transplanted stem cells travel to the bone marrow where they begin to make new blood cells over the next few weeks. It can take one or two years for the immune system to fully recover and function normally.

Kathryn B. Brown is a family nurse practitioner with a master's degree in nursing from OHSU. Is there a health topic you would like to read about? Send ideas to You can find more local health news and information in the Health section at