NELL-1-positive membranous nephropathy following gastric cancer in an older living kidney donor: a case report.

Living kidney transplantation is an established treatment for end-stage kidney disease (ESKD). While rare, the donors may develop de novo glomerular diseases post-donation. We report a case of membranous nephropathy (MN) in an 80-year-old male, diagnosed 9 years post-donation. The patient had a history of early gastric cancer treated with endoscopic submucosal dissection one year post-donation. Routine follow-up revealed asymptomatic proteinuria (4.27 g/gCr). The kidney biopsy demonstrated MN with IgG1/IgG3-dominant deposits and NELL-1 positivity. Recent evidence suggests NELL-1-positive MN may occur independently of malignancy in older individuals. Notably, MN developed 8 years after cancer remission with no evidence of recurrence. The patient achieved complete remission with conservative therapy consisting of an angiotensin receptor blocker and dietary modification. This case underscores the need for vigilant long-term follow-up in older kidney donors and illustrates how early proteinuria detection facilitates timely management of de novo glomerulopathies.