The fulminant form of post-transplant lymphoproliferative disorder (PTLD) is very uncommon and occurs in approximately 1% of PTLD patients. Approximately 85% of these lesions are of B-cell origin, and most of them are associated with Epstein-Barr virus infection. Fulminant PTLD is frequently associated with a systemic inflammatory response syndrome, and may be difficult to differentiate from septicemia. We describe the case of a 59-yr-old man who suffered from prolonged septicemia in the immediate post-transplant period, and presented again four months after cardiac transplantation with fever, painful liver edge and gastrointestinal bleeding. The diagnosis of fulminant PTLD with advanced multiorgan infiltration by a diffuse large-cell lymphoma of B-cell phenotype was made. During treatment with rituximab, the patient died from Enterococcus faecium septicemia. The sequence of septicemia, PTLD and, finally again, septicemia is an unusual challenge and urges for an aggressive diagnostic approach, where markers like procalcitonin may aid in the discrimination of fulminant PTLD from septicemia.