Pathophysiology
Immune complex deposition (post-streptococcal, IgA nephropathy, lupus nephritis, cryoglobulinaemia) or pauci-immune injury (ANCA-associated vasculitis) activates complement, neutrophils and macrophages within the glomerulus.
Sources: KDIGO 2021 Glomerular Diseases Guideline (Kidney Int 2021;100:S1); NEJM 2020;382:2432 - IgA Nephropathy
Clinical presentation
Post-streptococcal GN classically 1-3 weeks after pharyngitis or 3-6 weeks after impetigo: oedema (periorbital), hypertension, oliguria, tea-coloured urine in a child. IgA nephropathy: synpharyngitic (within 1-2 days of URI) macroscopic haematuria in adolescents.
Sources: KDIGO 2021 Glomerular Diseases Guideline (Kidney Int 2021;100:S1); NEJM 2020;382:2432 - IgA Nephropathy
Diagnosis
Urinalysis: dysmorphic RBCs, RBC casts, sub-nephrotic proteinuria. Bloods: creatinine rise, low C3 in post-streptococcal, lupus, MPGN, cryoglobulinaemia. Serologies: ASO/DNase B, ANA, dsDNA, ANCA, anti-GBM, hepatitis panel. Renal biopsy is definitive when diagnosis unclear or nephrology-worthy features present.
Sources: KDIGO 2021 Glomerular Diseases Guideline (Kidney Int 2021;100:S1); NEJM 2020;382:2432 - IgA Nephropathy
Management
Post-streptococcal GN is usually self-limiting - salt restriction, loop diuretic and antihypertensive. Treat underlying cause: steroids +/- cyclophosphamide/rituximab for ANCA/lupus; plasma exchange for anti-GBM and severe ANCA. Monitor for progression to chronic kidney disease.
Sources: KDIGO 2021 Glomerular Diseases Guideline (Kidney Int 2021;100:S1); NEJM 2020;382:2432 - IgA Nephropathy
