Matched sibling donor hematopoietic stem cell transplantation is the standard of care for severe aplastic anemia, with an overall survival of 80% to 90%. Only 60% to 70% of patients respond to treatment with immunosuppressive therapy. The main life threatening complications are infections, graft failure, and graft versus host disease. A 10-year-old patient with severe aplastic anemia underwent matched sibling donor hematopoietic stem cell transplantation, but developed sudden onset of fatal multiorgan failure on day +12. The cause of death was found only after autopsy.