Allogeneic Stem Cell Transplant for Patients With Severe Aplastic Anemia

Before patients receive any treatments, they will have the following: * Complete history and physical exam * Dental consultation * Bone marrow aspirate * Blood tests * Urinanalysis * Tests to look at your lungs (Chest X-ray and PFT's and DLCO) * Tests to look at your heart (EKG, MUGA, or echocardiogram) * Pregnancy test for females of childbearing age. Once the decision has been made by the patients to have a mismatched related or matched unrelated stem cell transplant, the patient will receive treatment called a "conditioning regimen" to prepare their body for the transplant. The purpose of this conditioning regimen is to kill the stem cells in the bone marrow, so that the patients immune system is suppressed (lowered or stopped from working), so their body will not reject the donors stem cells (transplant). The medicines which will be given as part of the conditioning regimen include Cyclophosphamide (Cytoxan) and Campath 1H. Both of these medications are approved by the Food and Drug Administration. Cyclophosphamide will be given for four days in a row. Cyclophosphamide is broken down into different chemicals and removed from the body in the urine. These different chemicals can cause bleeding in the bladder. Mesna is a drug that will be given with Cytoxan to prevent the build up of these chemicals that cause bleeding from the bladder. Campath 1H will also be given for four days. After the medicines, the patient will receive total body irradiation (TBI). Total body irradiation is strong doses of radiation (like x-rays) given to almost the whole body. One dose of TBI will be given to patients receiving a matched stem cell infusion while two doses of TBI will be given to patients receiving a mismatch stem cell infusion. After the conditioning regimen, the patient will then receive the stem cells (transplant). These stem cells will be given as an infusion (drip) into a vein. Patients will receive the drugs Tacrolimus (FK506) and Methotrexate to help prevent the complication of graft versus host disease. Methotrexate will be given on days 1, 3, 6 and 11 after they receive the stem cells. During this time, the patient will be on the stem cell transplant unit in protective isolation to help protect from developing infections. The following evaluations will be done as part of the stem cell transplant. EVALUATION DURING THE FIRST 100 DAYS: * Physical examination daily until discharged, then weekly. * Peripheral Blood for chimerism studies (looks at the presence of cells from the donor and from the patient existing together after the transplant) * Complete blood count (CBC) and platelets daily until discharge, then at least weekly * Blood chemistry (Electrolytes, BUN, creatinine, glucose, calcium, uric acid, total protein, albumin, ALT, AST, LDH, total bilirubin, LDH, magnesium) checked daily until discharge, then at least weekly * FK506 blood levels twice a week until discharge, then at least weekly * Blood tests for CMV (a type of virus) weekly DAY 100-365: * Physical examination at least monthly through Day 365 * Peripheral blood for chimerism studies * Follow-up for patients with chronic GVHD as needed * Chest X-ray * CBC and Blood chemistry tests as above checked monthly YEARLY EVALUATION: * Biopsies as needed (taking tissue samples for testing) * Chest x-ray * CBC and Blood chemistry evaluations as listed above * Peripheral blood for chimerism studies IMMUNOLOGIC TESTING: We will also be looking at the patients immune function. To do this, we will take 30 ml (2 tablespoonfuls) of blood every two weeks for two months, then monthly for 6 months, and then every 3 months for 2 years. When possible, the blood that is taken will be taken through an existing IV line. However, at times drawing the blood will require another stick with a needle. These blood tests will be done for research purposes as part of this study. All other blood tests listed above are done as part of good clinical care for patients receiving a stem cell transplant.