A JOURNEY THROUGH RENAL TRANSPLANTATION – FROM STABLE GRAFT FUNCTION TO AN UNEXPECTED DUODENAL NEUROENDOCRINE TUMOR

Renal transplant recipients require long-term surveillance for graft dysfunction, infections, drug toxicity and malignancy. We report a 44-year-old man with presumed chronic tubulointerstitial nephritis who underwent ABO-compatible living-related renal transplantation from his mother in July 2023. Initial graft function was excellent, with serum creatinine 1.3 mg/dL at discharge. Over the subsequent two years, creatinine gradually increased, followed in 2025 by recurrent diarrhea, vomiting and gastrointestinal bleeding. Evaluation demonstrated apoptotic enteropathy and later a well-differentiated grade 1 neuroendocrine tumor on duodenal biopsy, with synaptophysin positivity and Ki-67 1-3%. Ga-68 DOTATATE PET-CT showed subtle somatostatin-receptor-expressing lesions in the D3/D4 duodenum without regional or distant disease. Concurrently, progressive allograft dysfunction prompted graft biopsy, which was negative for rejection but showed IgA nephropathy with 40% interstitial fibrosis and tubular atrophy. MMF was withdrawn because of suspected drug-related diarrhea and replaced with azathioprine. Tacrolimus exposure was subsequently reduced after an elevated trough level. The patient was referred for multidisciplinary oncology management and commenced long-acting octreotide therapy. This case highlights the diagnostic complexity of progressive graft dysfunction in transplant recipients when gastrointestinal symptoms, medication toxicity, infection, chronic allograft injury and an unexpected neoplasm coexist.