Unusual Kidney Allograft Biopsy Findings of De Novo Membranous Glomerulonephritis and Focal Segmental and Global Glomerulosclerosis with Extracapillary Collapsing Lesions

Introduction: Membranous nephropathy (MN) can develop post kidney transplant, and is classified as recurrent disease in patients with a history of MN in the native kidneys or as de novo disease in those without such a history. The mechanism of recurrent MN is thought to be likely that of primary MN but de novo MN is not well delineated. The occurrence of collapsing glomerulopathy (CG) in renal allografts has been limited to case reports and small studies. We present a case of a patient with end stage kidney disease (ESKD) related to primary focal segmental glomerulosclerosis (FSGS), having undergone a living donor kidney transplant (LDKT), who developed massive proteinuria upward of 20-30 g/g and acute kidney injury. Case Description: 60 year old female with history of ESKD from primary FSGS, status post LDKT. She developed recurrent FSGS soon after and was placed on a regimen of twice weekly plasma exchange. Baseline Cr for nearly 8 years remained 0.6 - 0.8 mg/dL Proteinuria held steady at 4-6 g/g. She was later diagnosed with stage I squamous cell carcinoma of the lung, resected via right upper lobe lobectomy. Shortly after, proteinuria spiked to 20-30 g/g and serum albumin dropped to 2.7 g/dL. Plasma exchange was increased to thrice weekly and Rituximab 1000 mg given for presumed FSGS flare. Allograft biopsy surprisingly showed de novo membranous glomerulonephritis (MGN), favoring secondary form. Several glomeruli were segmentally and globally sclerotic with extracapillary lesions, the majority of which represented collapsing features. Discussion: Our report appears to be the first of its kind to describe this unusual constellation of glomerular processes in a renal allograft biopsy. MGN de novo (secondary favored) with focal segmental & global glomerulosclerosis with extracapillary lesions (majority with collapsing features) are difficut to interpret. It is unclear if the resecton of lung squamous cell carcinoma was an inciting factor, as the proteinuria rose to massive proportions afterward. All immunohistochemical stains of glomerular subepithelial deposits were negative. The presence of collapsing lesions was similarly perplexing. The presence of these rare lesions in the renal allograft should be kept in mind as one assesses for reproducibiity and potential explanations of pathogenesis.