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Immunoglobulin (Ig)A nephropathy (IgAN) is the most common primary glomerular disease worldwide and a leading cause of endstage kidney disease (ESKD). The pathogenesis of IgAN involves an interplay between genetic susceptibility and environmental factors, resulting in the overproduction of aberrantly glycosylated IgA1, and the production of glycan-specific IgA and IgG autoantibodies, deposition of immune complexes in the glomerulus and downstream mesangial cell activation, local inflammation, nephron injury and fibrosis.1 2 The data to date suggests interactions between gut microbiota, perturbed intestinal barrier, gut-associated lymphoid tissue and host genetic background pertinent to immune responsiveness in disease pathogenesis.3
The clinical course differs considerably between patients, with approximately 20%–30% of subjects going into long-term remission with stable kidney function, while about 30%–40% of patients progress to ESKD. Kidney biopsy provides the definitive diagnosis, and histological findings are reported according to the Oxford Classification for IgAN with scores assigned to mesangial hypercellularity (M0 or M1), segmental glomerulosclerosis (S0 or S1), endocapillary hypercellularity (E0 or E1), tubular atrophy/interstitial fibrosis (T0, T1, T2) and crescents (C0, C1 or C2) (MEST-C Score), since these items have been shown to independently predict renal outcome.4 Treatment decisions take into account clinical and histological parameters. Patients with insignificant proteinuria, normal renal function, normal blood pressure and no histological features portending poor prognosis may need only periodic monitoring. In the absence of proven therapy targeting disease-specific pathogenic pathways, blood pressure optimisation and renin–angiotensin–aldosterone system inhibition or blockade aiming for proteinuria reduction and ‘renal protection’ constitute the mainstay of management strategy. In the 2012 Kidney Disease Improving Global Outcomes (KDIGO) Clinical Practice Guidelines for Glomerulonephritis, the recommendation of ‘long-term ACE inhibitor (ACE-I) or angiotensin receptor blocker (ARB) treatment when proteinuria is >1 g/d, with up-titration of the drug depending on the blood pressure’ was the only one supported by Grade 1B evidence, while suggestions …
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
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Provenance and peer review Commissioned; internally peer reviewed.
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