A 25-year-old man presents with hematuria, proteinuria, hypertension, and reduced GFR after an upper respiratory tract infection. Biopsy shows diffuse mesangial IgA deposits on immunofluorescence. The pathognomonic immunofluorescence finding in IgA nephropathy is:

• A Linear IgG along the glomerular basement membrane
• B Subepithelial 'humps' of IgG and C3
• C Granular IgG and C3 in a 'lumpy-bumpy' pattern
• D Dominant mesangial IgA deposits ✓

Explanation

Berger's disease (IgA nephropathy) is defined by dominant or codominant mesangial IgA deposits on immunofluorescence, often with IgA1 containing undergalactosylated hinge-region O-glycans as the immunogen. Linear IgG is the hallmark of anti-GBM (Goodpasture) disease; subepithelial humps with IgG/C3 characterize post-streptococcal GN; lumpy-bumpy IgG/C3 is seen in post-infectious GN and lupus nephritis.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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