De novo glomerular diseases after renal transplantation

Abstract

Glomerular diseases developing in the kidney allograft are more often recurrences of the original disease affecting the native kidneys. However, in an undefined number of cases de novo, glomerular diseases unrelated to the original disease in the native kidneys can develop in the transplanted kidney. The clinical presentation and histologic features of de novo diseases are often similar to those features observed in patients with primary or secondary GN in the native kidneys. However, in transplanted kidneys, the glomerular, vascular, and tubulointerstitial changes are often intertwined with structural abnormalities already present at the time of transplant or caused by antibody- or cell-mediated allograft rejection, immunosuppressive drugs, or superimposed infection (most often of a viral nature). The pathophysiology of de novo glomerular diseases is quite variable. In rare cases of de novo minimal change disease, circulating factors increasing the glomerular permeability likely participate. Maladaptive hemodynamic changes and tissue fibrosis caused by calcineurin inhibitors or other factors may be involved in the pathogenesis of de novo FSGS. The exposure of cryptic podocyte antigens may favor the development of de novo membranous nephropathy. Many cases of de novo membranoproliferative GN are related to hepatitis C virus infection. Patients with Alport syndrome lacking antigenic epitopes in their glomerular basement membrane may develop antibodies against these glomerular basement membrane antigens expressed in the transplanted kidney. Infection may cause acute GN to have a heterogeneous clinical presentation and outcome. De novo pauci-immune GN in renal transplant is rare. Preexisting or acquired intolerance to glucose may, in the long term, cause diabetic nephropathy. The prognosis of de novo diseases depends on the type of GN, the severity of lesions caused by the alloimmune response, or the efficacy of immunosuppressive therapy. In most cases, the management of de novo glomerular diseases is empirical or elusive.

Keywords: GN; renal transplantation; transplant pathology.

Figure 1.

Glomerular lesions with membranoproliferative GN (MPGN) features at optical microscopy are today classified according to the results of immunofluorescence studies. Cases with glomerular deposition of Igs (IgG or IgM) are caused by circulating Igs or immune complexes and associated with other pathologic diseases, such as hepatitis B virus (HBV) or hepatitis C virus (HCV) infection, autoimmune diseases (systemic lupus erythematosus), or monoclonal gammopathy, including myeloma. In these cases, complement is frequently activated by the classic pathway. Cases without or with faint deposits of Igs are characterized by dominant deposits of C3. These cases are usually caused by congenital/hereditary mutations or acquired inhibitors (e.g., autoantibodies or monoclonal proteins) of factors regulating the alternative pathway of complement cascade. These latter disorders are called C3 glomerulopathies and can be subdivided into C3 GN and dense deposit disease according to electron microscopy findings.