Eltrombopag for Moderate Aplastic Anemia

Background: * Moderate aplastic anemia is a blood disease which may require frequent blood and platelet transfusions. Sometimes patients with this disease can be treated with immunosuppressive drugs. Not all patients respond and not all patients are suitable for this treatment. * Thrombopoietin (TPO) is a protein made by the body. The bone marrow needs TPO to produce platelets. TPO may also be able to stimulate bone marrow stem cells to produce red cells and white cells. However, TPO cannot be given by mouth. This has led researchers to develop the drug eltrombopag, which acts in the same way and can be given by mouth. Eltrombopag has been shown to safely increase platelet numbers in healthy volunteers and in patients with other chronic blood diseases, including severe aplastic anemia. Researchers are interested in looking at whether eltrombopag can be given to people with moderate aplastic anemia and significantly low blood cell counts. Objectives: \- To evaluate the safety and effectiveness of eltrombopag in people with moderate aplastic anemia or patients with bone marrow failure and unilineage cytopenia who need treatment for significantly low blood cell counts. Eligibility: \- People at least 2 years of age who have moderate aplastic anemia or bone marrow failure and unilineage cytopenia,and significantly low blood cell counts. Design: * Patients will be screened with a physical examination, medical history, blood tests, a bone marrow biopsy, and an eye exam. * Patients will receive eltrombopag by mouth once a day. * Patients will have weekly blood tests to monitor the effectiveness of the treatment and adjust the dose in response to possible side effects. * Patients may continue to take eltrombopag if their platelet count or hemoglobin increases, their requirement for platelet or blood transfusion decreases after 16 to 20 weeks of treatment, and there have been no serious side effects. Access to the drug will continue until the study is closed. Patients will be asked to return for a follow-up visit 6 months after the last dose of medication.