A 40-year-old woman with proteinuria 8 g/day and normal renal function undergoes renal biopsy. Light microscopy shows a 'spike and dome' pattern with periodic acid-methenamine silver stain, and IF shows granular IgG4 and PLA2R1 deposits. Which serological test is most useful for monitoring treatment response?
- A Anti-GBM antibody levels by ELISA
- B Serum complement C3 levels
- C Serum anti-PLA2R antibody titer by ELISA or IIFA ✓
- D Anti-dsDNA antibody titers
Explanation
Membranous nephropathy (MN) is characterized by subepithelial immune complex deposits giving the 'spike and dome' appearance. In approximately 70–80% of primary MN cases, the antigen is PLA2R1 (phospholipase A2 receptor), with IgG4 as the predominant IgG subclass. Anti-PLA2R antibody titers (serum ELISA or indirect immunofluorescence) predict disease activity, risk of progression, and response to therapy — declining titers precede proteinuria reduction by months. Immunological remission (negative anti-PLA2R) predicts clinical remission. Anti-GBM is relevant in Goodpasture syndrome; complement and anti-dsDNA are for lupus nephritis.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.