Severe aplastic anemia (SAA) is a rare condition in which white blood cells, red blood cells and platelets are low in the blood and the blood forming elements in bone marrow are either very few or absent.  As a result of the “empty” bone marrow, patients with SAA can be pale, and may experience fatigue (due to lower than normal red blood cells), infections (due to lower than normal white blood cells) and increased bruising and bleeding (due to lower than normal platelets).

What Causes Severe Aplastic Anemia?
SAA usually arises in a previously healthy child. While some cases of SAA have been linked to infections (e.g., hepatitis viruses), exposure to radiation and chemicals (including some medications), the exact cause is not known in most cases. It is likely that SAA is not one disease but rather a group of conditions, which present in a similar way. In addition, the mechanism whereby the bone marrow cells decrease in number can be a result of either autoimmune (i.e., immune system is working against itself) or other kind of injury of the blood forming cells.

What Are the Treatments Available for Severe Aplastic Anemia?
In order to prevent infections and bleeding, initially patients with SAA receive transfusions (platelets and red blood cells) and antibiotics. Once the patient is in stable condition, the treatment consists of drug therapy or bone marrow transplantation (BMT), or both.

Drug therapy involves use of medications (anti-thymocyte globulin, cyclosporine, steroids), which suppress the immune system and allow the blood forming capacity of bone marrow to recover. These medications need to be administered for a course of several months and are combined with a growth factor (G-CSF), which stimulates white blood cells to grow. Drug treatment, however, is effective in increasing the blood counts only in some patients. More importantly, the response may be short-lived and pre-malignant and malignant conditions may occur many years after treatment. Therefore, drug therapy is used by most physicians only in children who do not have a matched sibling donor, whose cells can be used as a source of stem cells for transplantation. 

Is Bone Marrow Transplantation the Best Option for Most Children with SAA?
Hematopoietic stem cells are immature cells, which can give rise to all cells in blood. The best donor of the stem cells is a brother or sister “matched” on the basis of tissue typing. Before infusion of donor stem cells, patients receive chemotherapy and radiation to suppress the patient’s abnormal bone marrow and to allow the new stem cells to grow and multiply in the recipient. When the matched sibling donor is not available, stem cells can be obtained from an unrelated donor’s matched bone marrow, circulating blood or umbilical cord blood. BMT is the only current treatment that provides a cure for children with aplastic anemia. BMT from a matched sibling donor should be recommended to all SAA patients who have one. BMT from an alternative donor should be recommended to all patients who have not responded to drug immunosuppressive therapy, or who have had a recurrence of their disease.