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IgA nephropathy

Abstract

Globally, IgA nephropathy (IgAN) is the most common primary glomerulonephritis that can progress to renal failure. The exact pathogenesis of IgAN is not well defined, but current biochemical and genetic data implicate overproduction of aberrantly glycosylated IgA1. These aberrant immunoglobulins are characterized by galactose deficiency of some hinge-region O-linked glycans. However, aberrant glycosylation alone is insufficient to induce renal injury: the participation of glycan-specific IgA and IgG autoantibodies that recognize the undergalactosylated IgA1 molecule is required. Glomerular deposits of immune complexes containing undergalactosylated IgA1 activate mesangial cells, leading to the local overproduction of cytokines, chemokines and complement. Emerging data indicate that mesangial-derived mediators that are released following mesangial deposition of IgA1 lead to podocyte and tubulointerstitial injury via humoral crosstalk. Patients can present with a range of signs and symptoms, from asymptomatic microscopic haematuria to macroscopic haematuria. The clinical progression varies, with 30–40% of patients reaching end-stage renal disease 20–30 years after the first clinical presentation. Currently, no IgAN-specific therapies are available and patients are managed with the aim of controlling blood pressure and maintaining renal function. However, new therapeutic approaches are being developed, building upon our ever-improving understanding of disease pathogenesis.

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Figure 1: The glomerulus in IgA nephropathy.
Figure 2: Global distribution of patients with IgA nephropathy in some key regions of the world.
Figure 3: Pathogenetic model of IgA nephropathy.
Figure 4: Structure and synthesis of human IgA1 O-glycans.
Figure 5: Pathways leading to glomerular damage, podocyte dysfunction and tubulointerstitial injury in IgA nephropathy.
Figure 6: Renal biopsy findings in a patient with IgA nephropathy.
Figure 7: Different stages of pathology in IgA nephropathy.
Figure 8: An algorithm of proposed treatment options for IgA nephropathy.

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Eleni Stamellou, Claudia Seikrit, … Rafael Kramann

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Contributions

Introduction (K.N.L.); Epidemiology (F.P.S.); Mechanisms/pathophysiology (J.N., Y.T. and K.N.L.); Diagnosis, screening and prevention (A.B.F., K.N.L. and S.C.W.T.); Management (K.N.L. and S.C.W.T.); Quality of life (R.J.G.); Outlook (K.N.L. and S.C.W.T.); Overview of the Primer (K.N.L.).

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Correspondence to Kar Neng Lai.

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Competing interests

S.C.W.T. is the recipient of the ‘Yu Professorship in Nephrology’ at the University of Hong Kong. F.P.S. has been supported by the grant QLG-1CT-2000-00464 from the European Framework Programme and the Schena Foundation, Bari, Italy. J.N. reports his current funding from the NIH, Bethesda, Maryland, USA, a gift from the IgA Nephropathy Foundation of America, and sponsored-research agreements with Pfizer and Anthera. J.N. is also a co-inventor on the US patent application 14/318,082 (assigned to UAB Research Foundation), and is a co-founder of Reliant Glycosciences, LLC. R.J.G. is a consultant for Abbvie, Astellas, Bristol-Myers Squibb, Chemocentryx, Eli Lilly, Mitsubishi, Sanofi-Genzyme, Wolters-Kluwer (UpToDate), Karger (American Journal of Nephrology and Karger Blog) and American Society of Nephrology (NephSAP). R.J.G. holds stock ownership in REATA, Inc. All other authors declare no competing interests.

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Lai, K., Tang, S., Schena, F. et al. IgA nephropathy. Nat Rev Dis Primers 2, 16001 (2016). https://doi.org/10.1038/nrdp.2016.1

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