Proliferative glomerulonephritis with monoclonal IgG deposits; an unusual cause of de novo disease in kidney allograft

Proliferative glomerulonephritis with monoclonal IgG deposits (PGNMID) is a newly described and rare entity that can develop in native and very rarely in transplanted kidneys. We present a patient who developed de novo PGNMID in the kidney allograft along with a review of the literature. A 38-year old female with type 1 diabetes who underwent successful simultaneous pancreas-kidney (SPK) transplantation 6 years earlier presented with rising serum creatinine, nephrotic range proteinuria and microhematuria. She underwent extensive work up and kidney allograft biopsy revealed mesangial expansion and hypercelluarity on light microscopy, mesangial staining for IgG3, kappa light chains, C1q and C3 on immunofluorescence and abundant mesangial electron dense deposits without substructures on electron microscopy. Serum and urine immunofixation electrophoresis were negative. A diagnosis of de novo PGNMID was made. Patient's proteinuria improved and serum creatinine stabilized with conservative therapy. PGNMID can rarely develop in kidney allograft as recurrent or de novo disease and may be mislabeled as transplant glomerulopathy if careful immunofluorescence and electron microscopy are not performed on biopsy specimens. Further studies are needed to better understand the pathogenesis of this disease entity and to develop optimal therapeutic approaches.