THSD7A-positive membranous nephropathy after kidney transplantation: A case report

Membranous nephropathy (MN) is a common cause of nephrotic syndrome after kidney transplantation (KT); however, scarce is known regarding post-KT thrombospondin type-1 domain-containing 7A (THSD7A)-positive MN. Herein, we report on a 72-year-old woman with end-stage kidney disease due to chronic interstitial nephritis (1996). In February 2020, she received a second deceased-donor KT, achieving optimal kidney function but presenting early post-KT proteinuria, reaching up to 1800mg/24h six months after transplantation, controlled with renin-angiotensin-aldosterone system (RAAS) blockade. In July 2021, a kidney allograft biopsy revealed features consistent with MN. Immunohistochemical stains showed diffuse and granular THSD7A and C4d deposition in glomerular capillary walls and negative PLA2R and IgG4 staining. No anti-THSD7A antibodies were detected in the serum. The pre-implantation biopsy showed no MN-associated lesions and negative THSD7A staining. Secondary triggers such as malignancy were discarded. The present report illustrates a THSD7A-positive MN in a KT recipient. Despite lacking native kidney biopsy and early presentation, a recurrent MN seemed unprovable due to documented native kidney disease and a long time span between native kidney disease and MN diagnosis. We, therefore, presumed primary de novo disease. Two years after KT, kidney function remains stable, and the patient has reached complete remission of proteinuria.