Bone marrow transplantation in children with sickle cell disease

Bone marrow transplantation (BMT) is currently the only known cure for sickle cell disease. It involves replacing the abnormal stem cells residing in bone marrow with healthy cells from an eligible brother or sister. This procedure is also sometimes called a stem cell transplant.

What is bone marrow?

Bone marrow is a sponge-like tissue within the bones that functions as a “factory” and produces all the blood cells for the body. Its stem cells produce red cells, platelets and white cells. People with sickle cell disease have bone marrow stem cells that produce abnormal red cells which contain defective sickle hemoglobin.

How does a patient receive a bone marrow transplant?

To create space in the bone marrow for the healthy stem cells, a child with sickle cell disease is treated with chemotherapy to eliminate his or her own unhealthy bone marrow. Then, he or she receives healthy bone marrow cells (donated by a brother or sister) through a vein, similar to a blood transfusion. Surgery is usually not involved.

How does a brother or sister donate healthy bone marrow cells?

The cells of the healthy, full brother or sister who donates are usually collected through a process called a stem cell harvest. There are three different ways to harvest stem cells.

The first and most common is peripherally, or through the veins. The donor is given a medicine to stimulate stem cell growth in the blood. Then, the donor’s blood is drawn from a vein. The blood runs through a pheresis machine, which collects the stem cells from the donor’s blood and then puts the blood back into his or her veins.

If the donor has very small veins, stem cells can instead be collected through the pelvic bone. During this kind of stem cell harvest, the donor is put to sleep by anesthesia and a small needle is placed in the pelvic bone. The bone marrow, which resembles blood, is then pulled into a regular syringe. After enough cells are collected, the needle is removed, the child awakens from anesthesia and is usually able to return home the same day. The site of the bone marrow harvest may be sore for a few days. The donor’s healthy bone marrow quickly grows new cells to replace those taken during the stem cell harvest. This process of replacement is similar to what happens when adults donate blood.

The third possible way of making a stem cell harvest is by collecting cells from a sibling’s umbilical cord, if those cells were stored at the sibling’s time of birth.

Is my child a candidate for a bone marrow transplant?

Your child is a candidate if he or she has:

  • Complications due to sickle cell disease such as stroke,
  • frequent pain episodes,
  • frequent chest crisis, or
  • abnormal MRI or ultrasound of the brain

and

  • Has a full brother or sister who does not have sickle cell disease and
  • who has a closely matching bone marrow.

Not all brothers and sisters of a patient with sickle cell disease are full matches for bone marrow. However, a sibling who has the sickle cell trait may also donate bone marrow.

What are some of the risks of bone marrow transplants?

While the majority of children do well after bone marrow transplantation, there are possible risks.

Once the new stem cells are injected into the bloodstream of the child with sickle cell disease, it may take several weeks for the new stem cells to grow. Your child will remain in the hospital for approximately two to three weeks while the new stem cells grow in the bone marrow.

During this time, the child is at risk for infection or bleeding. Infection or bleeding may be severe and, in rare cases, may cause death.

In some cases, the transplant may fail, leading to the return of the sickle cell disease. Other risks are possible and you should discuss this with your doctor in detail.

My child doesn’t have a full sibling. Can other family members or people in the general population donate stem cells?

Currently, only full siblings whose bone marrow closely matches can donate stem cell cells for transplant in sickle cell disease. Texas Children’s Hospital is conducting research so that in the future, donors may also be siblings who share only one parent, other relatives, or other members of the public who match with your child.