[Post-transplant lymphoproliferative disorder localized to the colon presented with mild diarrhea after cord blood transplantation].

Post-transplant lymphoproliferative disorder (PTLD) usually develops with systemic symptoms, such as fever, generalized lymphadenopathy, and elevation in the lactate dehydrogenase level. Here, we present the case of a 65-year-old female patient with PTLD localized to the colon; the patient only had mild diarrhea without systemic symptoms. She had myelodysplastic syndrome and was treated with cord blood transplantation (CBT). She had a past medical history of sigmoid colon cancer treated with colonosectomy and adjuvant chemotherapy. After CBT, she achieved complete remission and was discharged after 60 days. Further, 79 days after CBT, she presented with abdominal pain. Computed tomography scan revealed adhesive ileus. The abdominal pain was resolved in 1 day with conservative treatment, however, mild diarrhea persisted. Therefore, we performed colonoscopy and found multiple ulcerative lesions in the upper colon. A pathological examination revealed PTLD. Furthermore, elevation of EBV-DNA in the blood was also confirmed. There was no detectable lesion on positron emission tomography-computed tomography (PET-CT) outside the colon; thus, we diagnosed PTLD localized into the colon that was successfully treated with rituximab. Our present experience suggests that it might be important to perform endoscopy and monitoring of EBV-DNA for early detection of PTLD, especially localized in the gastrointestinal tract.