Severe graft-versus-host disease post allogeneic hematopoietic stem cell transplantation due to loss of HLA heterozygosity in recipient lymphocytes after full graft rejection.

Germ cell tumors complicated by hematological malignancy (HM) are a rare clinical phenomenon. Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a potentially effective therapy, but graft-versus-host disease (GVHD) is a life-threatening complication. We report a case of a 13-year-old female patient diagnosed with germ cell tumors followed by acute lymphoblastic leukemia. After chemotherapy, she received allo-HSCT and her chimerism rate decreased rapidly to near zero by 6 months without evidence of HM recurrence. However, she developed severe, multiorgan GVHD-like manifestations. DNA analysis revealed the pathogenesis of GVHD to be loss of HLA heterozygosity in recipient hematopoietic cells.