Neuropsychological Effects of Immunosuppressive Treatment in Subjects With Aplastic Anemia

This study will use neuropsychological tests to look at nervous system side effects of Cyclosporine (CsA) in patients with aplastic anemia. CsA is used as part of an immunosuppressive regimen in treating severe aplastic anemia. The drug can produce nervous system side effects, such as tremor and, less commonly, insomnia, anxiety, headache, confusion or seizures. This study will look at effects of CsA on intellectual ability, depression, anxiety, attention, concentration, memory, perception, coordination, and thought processing in patients Patients 15 years of age or older who have severe aplastic anemia may be eligible for this study if they: * are co-enrolled in a Clinical Center protocol in which they will receive CsA * have not taken CsA for 6 months before enrolling in this study Participants undergo neuropsychological testing. In addition, they provide blood samples and their clinical data are reviewed for things that may influence the interpretation of findings from the testing, such as results of blood tests, types of medications taken, number of transfusions required, etc. The procedures are as follows: Before first dose of cyclosporine: * Patients are asked about prior problems with their nervous system, prior treatment for their aplastic anemia (including transfusions), prior infections, and current medications. They then complete the following sets of tests: * Battery 1: A set of three tests that measure intellectual ability, level of depression (if any) and level of anxiety (if any). * Battery 2: A set of seven tests that measure changes in the central nervous system and how these changes affect attention, concentration, memory, perception, coordination, and thought processing. * Patients provide a half teaspoon of blood for this study at the same time blood is collected for their primary treatment protocol. 6 months and 12 months after starting cyclosporine * Patients are asked about treatment for their aplastic anemia (including transfusions), infections, and changes in medications that have occurred since they started taking cyclosporine. They then repeat the set of tests in Battery 2. * Patients provide a half teaspoon of blood for this study at the same time blood is collected for their primary treatment protocol.