A 4-year-old boy presented 14 months after liver and small bowel transplantation with fever, diarrhea, elevated liver enzymes, thrombocytopenia and autoantibodies. Total gammaglobulins level was normal but the level of plasma IgA1 was very high. The blood PCR for Epstein-Barr virus (EBV) was negative. The ileal biopsy disclosed a lymphoplasmacytic infiltration. The EBER probe was negative on the small bowel biopsies. The child was considered as suffering from a non-EBV-induced posttransplant lymphoproliferative disorder (PTLD). The high IgA level was presumed to be secreted by proliferating plasma cells in the transplanted bowel. Immunosuppression was reduced; but the efficacy was incomplete and an anti-CD20 antibody was added. There was complete resolution of symptoms and normalization of the IgA level. As IgA1 is mostly of intestinal origin, this unusual presentation of PTLD should lead to a high suspicion of a small bowel proliferating process.