Iga Nephropathy

Key points

• IgA nephropathy (IgAN; Berger disease) is the most common primary glomerular disease worldwide and is an important cause of CKD and kidney failure.
• Associations/contexts: IgAN can occur with chronic liver disease including cirrhosis and with inflammatory/infectious conditions; IgA vasculitis is a related systemic disease rather than simply an association.
• Pathophysiology: IgA-containing immune complexes deposit predominantly in the mesangium, producing mesangial inflammation/injury; IgAN and IgA vasculitis share important pathogenic features.
• Histology: mesangial hypercellularity/proliferation may be seen, and immunofluorescence demonstrates dominant or co-dominant IgA , often with C3, in glomerular deposits.
• Classic presentation: recurrent visible haematuria, often occurring during or within a few days of an upper-respiratory infection ( synpharyngitic haematuria ); persistent microscopic haematuria and proteinuria are also common.
• Nephrotic-range proteinuria can occur and is associated with greater risk; kidney function may remain preserved or may progressively decline depending on risk factors and disease severity.
• Key distinction from post-infectious GN: IgAN typically causes haematuria during/within days of the infection and usually has normal complement; post-infectious GN typically has a latent interval of weeks and low C3.
• MRCP discriminator: synpharyngitic haematuria = IgAN; haematuria weeks after infection + low C3 = post-infectious GN.
• Current update: KDIGO 2025 emphasises risk-based supportive care and targeted therapies for eligible patients; do not teach 'IgAN is always benign' or 'nephrotic proteinuria is rare' as absolute rules.