Proliferation of macrophage-lineage cells in the bone marrow, severe thymic atrophy, and extramedullary hematopoiesis of possible donor origin in an autopsy case of post-transplantation graft-versus-host disease

A case of proliferation of CD68-positive macrophage-lineage cells in the bone marrow accompanied by severe thymic atrophy associated with graft-versus-host disease (GVHD) in a boy given allogeneic bone marrow transplantation (BMT) is reported. A 7-year-old boy was treated for posthepatitic severe aplastic anemia by BMT from his HLA-identical, mixed lymphocyte reaction-negative sister. After the transplantation his peripheral blood group converted to the donor type. However, the patient suffered from acute and chronic GVHD and slowly progressive anemia, and he died of multiple organ failure 21 months after BMT. At the autopsy diffuse and monotonous proliferation of CD68-positive macrophage-lineage cells was found to be replacing the blood-forming cells in the bone marrow. The thymus was almost empty of T lymphocytes, and remaining strands of extremely atrophic epithelial cells showed focal cystic change. Extramedullary hematopoiesis was found in the spleen. Analyses of microsatellite markers suggested the hematopoietic cells in the spleen to be of donor origin.