Selective engraftment of the granulocyte compartment after allogeneic bone marrow transplantation in a patient with severe aplastic anemia.

PURPOSE: We present a patient with severe aplastic anemia who had partial engraftment with full chimerism after allogeneic bone marrow transplantation from an HLA identical sibling.

PATIENTS AND METHODS: A 3-year-old girl with severe aplastic anemia (SAA) received a bone marrow transplantation (BMT) from an HLA identical brother 9 months after her diagnosis. Before BMT she was red blood cell tranfusion dependent, had an absolute neutrophil count (ANC) of 1,000-1,500 x 10(9)/1 and a platelet count of 15-19,000 x 10(9)/1. She was conditioned with 800 cGy total body irradiation (TBI) and cyclophosphamide and received 3X10(8) nucleated cells/kg.

RESULTS: She reached an ANC of 1500 x 10(9)/1 on day +35 but her reticulocyte and platelet counts did not recover. A bone marrow aspirate and biopsy post BMT showed hypoplasia with marked decrease in megakaryocyte and red blood cell precursors. The granulocyte compartment showed a left shift with predominance of promyelocytes and myelocytes. The karyotype showed full chimerism (46,XY) with no 46,XX metaphases.

CONCLUSION: This case illustrates the possibility of a bone marrow microenvironment defect as the cause of SAA.