n HOW IS APLASTIC ANEMIA CLASSIFIED OR STAGED? The International Aplastic Anemia Study Group has identified specific criteria for the blood and bone marrow values. This criteria is used in the staging of aplastic anemia. The values in the blood are • ANC less than 500 (normal is greater than 1,000) • platelet count less than 20,000 (normal is 150,000–400,000) • reticulocyte count less than 1%. The values in the bone marrow are • bone marrow biopsy with less than 25% of normal cellularity • bone marrow biopsy less than 50% of normal cellularity with the blood-forming cells representing less than 30% of all cells. Severe aplastic anemia (SAA) is defined by meeting at least two of the three criteria for blood and either of the marrow criteria. Very severe aplastic anemia (VSAA) includes the above diagnosis of severe aplastic anemia, but with an ANC less than 200.
n HOW IS APLASTIC ANEMIA TREATED?
HLA Typing Your child’s physician may order human leukocyte antigen (HLA) typing to determine if a bone marrow transplant is a recommended treatment option. HLA typing can be done through a blood sample or a swab on the inside of the cheek. This often is done on the child diagnosed with aplastic anemia, any siblings, and parents. This testing can determine if there is a family member who may be a possible donor for bone marrow transplant or if a search for an unrelated person is needed. HLA are proteins or markers found on the surface of most cells in the body. The immune system uses these markers to recognize which cells belong in your body and which do not. A child generally inherits
half of his or her HLA markers from their mother and half from their father. Siblings who have the same parents have a 25% chance of having the same proteins. When two people share the same HLA pro- teins, this is called a “match.” A biologic parent is generally only half matched, or haploidentical, to their child. For a parent to be matched with his or her child, both parents must by chance have some HLA genes in common with each other. There is only a one in 200 chance that a parent and child will be HLA matched. A close match between a donor’s and a patient’s HLA markers is essential for a successful transplant outcome. Immune Suppression Aplastic anemia is thought to be an autoimmune disorder in which the body’s own immune system attacks the blood-forming cells. Medica- tions that suppress the immune system are used to try to stop this process from continuing. For children who do not have an available matched related bone marrow donor, immunosuppressive therapy is
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