Is de novo membranous nephropathy suggestive of alloimmunity in renal transplantation? A case report.

Background: Post-transplant nephrotic syndrome (PTNS) in a renal allograft carries a 48% to 77% risk of graft failure at 5 years if proteinuria persists. PTNS can be due to either recurrence of native renal disease or de novo glomerular disease. Its prognosis depends upon the underlying pathophysiology. We describe a case of post-transplant membranous nephropathy (MN) that developed 3 mo after kidney transplant. The patient was properly evaluated for pathophysiology, which helped in the management of the case.

Case summary: This 22-year-old patient had chronic pyelonephritis. He received a living donor kidney, and human leukocyte antigen-DR (HLA-DR) mismatching was zero. PTNS was discovered at the follow-up visit 3 mo after the transplant. Graft histopathology was suggestive of MN. In the past antibody-mediated rejection (ABMR) might have been misinterpreted as de novo MN due to the lack of technologies available to make an accurate diagnosis. Some researchers have observed that HLA-DR is present on podocytes causing an anti-DR antibody deposition and development of de novo MN. They also reported poor prognosis in their series. Here, we excluded the secondary causes of MN. Immunohistochemistry was suggestive of IgG1 deposits that favoured the diagnosis of de novo MN. The patient responded well to an increase in the dose of tacrolimus and angiotensin converting enzyme inhibitor.

Conclusion: Exposure of hidden antigens on the podocytes in allografts may have led to subepithelial antibody deposition causing de novo MN.