Role of light and immunofluorescence microscopy to differentiate primary and secondary membranous nephropathy

Context: Membranous nephropathy (MN) causes nephrotic syndrome, mostly primary but may be associated with SLE, infections, cancer, or drug. Aims: To estimate clinical, serological, light microscopic, and direct immunofluorescence (DIF) findings to differentiate primary and secondary MN. Settings and Design: Prospective, cross-sectional, single-center study in a tertiary care hospital. Methods and Material: Total 51 cases from September 2019 to February 2020. Laboratory Data: Blood glucose, urine analysis, urea, creatinine, albumin, cholesterol, HBsAg, Anti HCV, ASO, ANA, MPO ANCA, PR3 ANCA, dsDNA, PLA2R, C3, and C4. Clinical parameters: age, sex, BP, skin lesions, arthralgia, edema, obesity. Renal biopsies examined with H and E, PAS, silver methanamine, MT stains. DIF done with IgG, IgM, IgA, C3c, C1q, kappa, and lambda. Statistical Analysis Used: Statistical software (Graph Pad PRISM 6) and Chi-square test). Results: Among 51 cases, 25 are primary and 26 are secondary MN with 22 being lupus nephritis, with 2 being post-infectious and the remaining 2 being proliferative glomerulonephritis with monoclonal immunoglobulin deposition (PGNMIDD) with kappa chain restriction. Mean age was 37 ± 12.18 and 30.69 ± 13.92 years for primary and secondary MN, respectively. Significant male preponderance in primary MN. Serum C4 significantly low in secondary MN (15.34 ± 9.59). Microscopic hematuria present in secondary MN. Mesangial and endocapillary hypercellularity are significant in secondary MN. IgG and kappa are significantly intense in primary whereas IgA, C3c, and C1q are significantly intense in secondary MN. Conclusions: Reliable differentiation between primary and secondary MN has important therapeutic implications.