Recovery from aplastic anemia following attempted marrow transplantation

A 23-year-old man with severe idiopathic aplastic anemia was prepared for marrow transplantation by the administration of cyclophosphamide (CY) 50 mg/kg on each of 4 days. He then received an intravenous infusion of 9.5 x 10(9) marrow cells from an HL-A matched and mixed leukocyte culture non-reactive sister. The graft was successfully established as shown by cytogenetic studies but was rejected after approximately 4 weeks. In preparation for a second transplant he was given procarbazine 12.5 mg/kg and goat antihuman thymocyte globulin (ATG) 7 mg/kg administered on alternate days for a total of 4 doses of each agent. At the end of this therapy his white blood cell count was noted to be going up and the second transplant was not carried out. Complete hematologic recovery of host type marrow ensued and persists now 20 months later. The various pathophysiologic mechanisms that may be involved are discussed.