OBJECTIVES: I. Evaluate the efficacy of related, HLA-identical bone marrow transplantation following cyclophosphamide (CTX) and antithymocyte globulin in patients with aplastic anemia.

II. Evaluate the efficacy of related, HLA-nonidentical bone marrow transplantation following CTX and total-body irradiation/total-lymphoid irradiation in patients with aplastic anemia.

PROTOCOL OUTLINE: Patients with HLA-identical donors receive cyclophosphamide/mesna, antithymocyte globulin (ATG), and methylprednisolone (MePRDL), followed by allogeneic marrow transplantation.

Patients with HLA-nonidentical (5/6 or 4/6) donors and those with a systemic reaction to ATG receive the same dosage of myeloablative chemotherapy and rescue. In addition, these patients are treated with total-body irradiation, total-lymphoid irradiation, and methotrexate.

All patients received MePRDL and cyclosporine for graft-versus-host prophylaxis.

PROTOCOL ENTRY CRITERIA:

--Disease Characteristics-- Severe aplastic anemia with 2 of the following criteria: Polymorphonuclear neutrophils no more than 0.5 x 10 to the ninth/L Platelets no more than 20 x 10 to the ninth/L Reticulocytes no more than 30 x 10 to the ninth/L Hypocellular bone marrow Related donor aged 6 weeks or more, matching at least 4 of 6 HLA A, B, and DRI loci, as follows: HLA-identical family member for patients aged less than 40 years HLA-nonidentical family member for patients aged less than 55 years failing antithymocyte globulin or other immunosuppressive therapy The following eligible for transplantation as initial therapy: Patients aged less than 40 years with HLA-matched donor Patients aged 40-45 years with HLA-identical donor No neoplastic or preneoplastic evolution --Patient Characteristics-- Age: Under 40 (55 if ATG failure) Hepatic: No severe liver dysfunction Renal: No severe renal dysfunction Cardiovascular: No severe cardiac dysfunction Other: No other organ dysfunction that would compromise survival after transplant No HIV infection