Paraskevas Iatropoulos1, Marina Noris1, Caterina Mele1, Rossella Piras1, Elisabetta Valoti1, Elena Bresin1, Manuela Curreri1, Elena Mondo2, Anna Zito1, Sara Gamba1, Serena Bettoni1, Luisa Murer3, Veronique Fremeaux-Bacchi4, Marina Vivarelli5, Francesco Emma5, Erica Daina6, Giuseppe Remuzzi7. 1. IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, Clinical Research Center for Rare Diseases Aldo e Cele Daccò, Ranica, Bergamo, Italy. 2. Unit of Nephrology and Dialysis, Azienda Ospedaliera Papa Giovanni XXIII, Bergamo, Italy. 3. Unit of Pediatric Nephrology, Dialysis and Transplantation, Azienda Ospedaliera of Padova, Italy. 4. Department of Immunology, Assistance Publique-Hopitaux de Paris, Hopital Europeen George-Pompidou and INSERM UMRS 1138, Cordelier Research Center, Complement and Diseases Team, Paris, France. 5. Division of Nephrology and Dialysis, Bambin Gesù Pediatric Hospital, Roma, Italy. 6. IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, Clinical Research Center for Rare Diseases Aldo e Cele Daccò, Ranica, Bergamo, Italy. Electronic address: erica.daina@marionegri.it. 7. IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, Clinical Research Center for Rare Diseases Aldo e Cele Daccò, Ranica, Bergamo, Italy; Unit of Nephrology and Dialysis, Azienda Ospedaliera Papa Giovanni XXIII, Bergamo, Italy; Department of Biomedical and Clinical Sciences, University of Milan, Milan, Italy.
Abstract
BACKGROUND: Membranoproliferative glomerulonephritis (MPGN) is an uncommon cause of chronic nephropathy recently reclassified into immunoglobulin-associated MPGN (Ig-MPGN) and C3 glomerulopathy (C3G). In this study we aimed: (1) to evaluate the complement genetic and biochemical profile in patients with Ig-MPGN/C3G; (2) to investigate whether genetic variants and different patterns of complement activation (i.e., fluid versus solid phase) correlate with disease manifestations and outcomes. METHODS: In 140 patients with idiopathic Ig-MPGN or C3G we performed complement biochemical and genetic screening and correlated genetic, biochemical and histology data with clinical features. RESULTS: Mutations in genes encoding alternative pathway complement proteins were found in both Ig-MPGN and C3G, and mutations in the two components of the C3 convertase are the most prevalent. We also report a mutation in THBD encoding thrombomodulin in a C3G patient. The presence of mutations alone does not significantly increase the risk of Ig-MPGN or C3G, but it does so when combined with common susceptibility variants (CD46 c.-366A in Ig-MPGN; CFH V62 and THBD A473 in C3G). Finally, patients without complement gene mutations or C3NeFs--autoantibodies that stabilize the alternative pathway C3 convertase--have a higher risk of progressing to end-stage renal disease than patients with identified mutations and/or C3NeFs, suggesting the existence of different pathogenetic mechanisms that lead to renal disease. CONCLUSIONS: We provide new insights into the pathogenesis of Ig-MPGN/C3G that underscore the complex nature of these diseases and suggest that the current C3G classification may miss many cases associated with abnormalities of the complement alternative pathway.
BACKGROUND: Membranoproliferative glomerulonephritis (MPGN) is an uncommon cause of chronic nephropathy recently reclassified into immunoglobulin-associated MPGN (Ig-MPGN) and C3 glomerulopathy (C3G). In this study we aimed: (1) to evaluate the complement genetic and biochemical profile in patients with Ig-MPGN/C3G; (2) to investigate whether genetic variants and different patterns of complement activation (i.e., fluid versus solid phase) correlate with disease manifestations and outcomes. METHODS: In 140 patients with idiopathic Ig-MPGN or C3G we performed complement biochemical and genetic screening and correlated genetic, biochemical and histology data with clinical features. RESULTS: Mutations in genes encoding alternative pathway complement proteins were found in both Ig-MPGN and C3G, and mutations in the two components of the C3 convertase are the most prevalent. We also report a mutation in THBD encoding thrombomodulin in a C3G patient. The presence of mutations alone does not significantly increase the risk of Ig-MPGN or C3G, but it does so when combined with common susceptibility variants (CD46 c.-366A in Ig-MPGN; CFH V62 and THBD A473 in C3G). Finally, patients without complement gene mutations or C3NeFs--autoantibodies that stabilize the alternative pathway C3 convertase--have a higher risk of progressing to end-stage renal disease than patients with identified mutations and/or C3NeFs, suggesting the existence of different pathogenetic mechanisms that lead to renal disease. CONCLUSIONS: We provide new insights into the pathogenesis of Ig-MPGN/C3G that underscore the complex nature of these diseases and suggest that the current C3G classification may miss many cases associated with abnormalities of the complement alternative pathway.
Authors: Maria Chiara Marinozzi; Lubka T Roumenina; Sophie Chauvet; Alexandre Hertig; Dominique Bertrand; Jérome Olagne; Marie Frimat; Tim Ulinski; Georges Deschênes; Stephane Burtey; Michel Delahousse; Bruno Moulin; Christophe Legendre; Véronique Frémeaux-Bacchi; Moglie Le Quintrec Journal: J Am Soc Nephrol Date: 2017-01-17 Impact factor: 10.121