IgA Nephropathy in Adults

Importance: IgA nephropathy (IgAN) is a chronic kidney disease involving deposition of IgA-containing immune complexes in the glomerulus, causing glomerular inflammation and scarring. It is the most common immune-mediated glomerular disease worldwide, and affects an estimated 198 887 to 208 184 persons in the US. Up to 50% of patients with IgAN develop kidney failure within 10 years of diagnosis. Observations: IgAN typically presents with nephritic syndrome and usually occurs in younger adults, with a mean age at diagnosis of 34 to 45 years. Incidence is highest in East Asia. Approximately 60% of cases are detected incidentally with hematuria or proteinuria on urinalysis. Up to 30% of patients present with episodic visible hematuria, often concomitantly with an upper respiratory or gastrointestinal tract infection (synpharyngitic hematuria). Less common presentations include nephrotic syndrome (<5%) and rapidly progressive glomerulonephritis (<5%). When IgAN is suspected (due to hematuria, proteinuria, or reduced kidney function), initial workup should include quantification of proteinuria and assessment for other causes of nephritic syndrome (eg, lupus nephritis). Adults with suspected IgAN and proteinuria greater than or equal to 0.5 g per day should undergo kidney biopsy. The diagnosis of primary IgAN is based on presence of IgA-dominant immune deposits in the glomerular mesangium after excluding other causes of this histologic appearance, ie, IgA vasculitis, IgA-dominant infection-related glomerulonephritis, and secondary IgAN from diseases such as cirrhosis, inflammatory bowel disease, celiac disease, infection (eg, viral hepatitis), and autoimmune diseases (eg, axial spondyloarthritis). Based on the Kidney Disease: Improving Global Outcomes 2025 clinical practice guideline for the management of IgAN, treatment for patients with proteinuria greater than 0.5 g per day includes behavioral modifications (eg, dietary sodium <2 g/d, smoking cessation, weight control, exercise), antihypertensive medications for goal blood pressure less than 120/70 mm Hg, and therapies to reduce the formation of IgA-containing immune complexes (eg, targeted-release budesonide), decrease glomerular injury (eg, systemic glucocorticoids, iptacopan), and manage existing IgAN-induced nephron loss (eg, renin-angiotensin system inhibitor or dual endothelin angiotensin receptor antagonist [eg, sparsentan] alone or in combination with a sodium-glucose cotransporter 2 inhibitor). Conclusions and Relevance: IgAN is the leading cause of immune-mediated glomerular disease worldwide. Patients with suspected IgAN and proteinuria greater than or equal to 0.5 g per day should undergo kidney biopsy to confirm the diagnosis. Treatment of IgAN includes behavioral modifications, blood pressure management, and therapies to decrease formation of IgA-containing immune complexes (eg, targeted-release budesonide), reduce immune complex-mediated glomerular injury (eg, systemic glucocorticoids, iptacopan), and manage IgAN-induced nephron loss (eg, renin-angiotensin system inhibitor, dual endothelin angiotensin receptor antagonist, and sodium-glucose cotransporter 2 inhibitor).