👤 Nicole K Andeen

Membranous nephropathy (MN) is the cause of 3% of pediatric nephrotic syndrome, with increasing incidence in adolescents. It was historically divided into primary and secondary forms but is increasingly described by antigen. The direct clinical value of knowing the MN antigen often depends on the strength of association between antigen and various underlying conditions, prognostic potential, and the presence of commercially available serum antibody testing. In this case, we describe an adolescent with PLA2R-, NELL1-, THSD7A-, and EXT2-negative MN who responded to B-cell depleting therapy. Three years later, he developed proliferative lupus nephritis and ongoing membranous nephritis with newly detected EXT2-positive deposits on kidney biopsy. This discordant MN antigen result demonstrates (1) the potential for apparent change in MN antigen detection over time and (2) that EXT1/2 negativity does not exclude the possibility of later development of lupus nephritis in an adolescent with MN. Show less

Recent progress in glomerular immune complex and complement-mediated diseases have refined diagnostic categories and informed mechanistic understanding of disease development in pediatric patients. Herein, we discuss selected advances in 3 categories. First, membranous nephropathy antigens are increasingly utilized to characterize disease in pediatric patients and include phospholipase A2 receptor (PLA2R), Semaphorin 3B (Sema3B), neural epidermal growth factor-like 1 (NELL1), and protocadherin FAT1, as well as the lupus membranous-associated antigens exostosin 1/2 (EXT1/2), neural cell adhesion molecule 1 (NCAM1), and transforming growth factor beta receptor 3 (TGFBR3). Second, we examine advances in techniques for paraffin and light chain immunofluorescence (IF), including the former's function as a salvage technique and their necessity for diagnosis in adolescent cases of membranous-like glomerulopathy with masked IgG kappa deposits (MGMID) and proliferative glomerulonephritis with monotypic Ig deposits (PGNMID), respectively. Finally, progress in understanding the roles of complement in pediatric glomerular disease is reviewed, with specific attention to overlapping clinical, histologic, and genetic or functional alternative complement pathway (AP) abnormalities among C3 glomerulopathy (C3G), infection-related and post-infectious GN, "atypical" post-infectious GN, immune complex mediated membranoproliferative glomerulonephritis (IC-MPGN), and atypical hemolytic uremic syndrome (aHUS). Show less