Repeated Kidney Biopsy in Membranoproliferative Glomerulonephritis

Area of Science:

• Nephrology
• Pathology
• Immunology

Background:

• Membranoproliferative glomerulonephritis (MPGN) is a complex glomerular disease with heterogeneous presentations.
• Accurate diagnosis and pathogenic understanding of MPGN often require serial investigations.

Purpose of the Study:

• To evaluate the diagnostic yield of repeated kidney biopsies in patients with MPGN.
• To assess changes in clinical and pathological findings and reclassification rates, particularly for monoclonal gammopathy of renal significance (MGRS).

Main Methods:

• Retrospective analysis of clinical and pathological data from 82 patients with MPGN who underwent at least two kidney biopsies.
• Comparison of findings between initial and subsequent biopsies, including proteinuria, estimated glomerular filtration rate (eGFR), and renal complement deposition.
• Analysis of etiological reclassification, focusing on the distinction between idiopathic MPGN and MGRS.

Main Results:

• Approximately 28% of MPGN patients underwent repeat biopsies, a higher incidence than in other glomerulonephropathies under immunosuppression.
• Repeat biopsies revealed significant increases in proteinuria and renal C3 deposition, along with a decline in eGFR.
• Thirty-seven percent of patients were reclassified etiologically, predominantly to MGRS, which was associated with older age and poorer renal function but slower eGFR decline compared to idiopathic MPGN.
• A significant proportion of MGRS patients (64%) tested negative for monoclonal proteins in initial serum or urine immunofixation.

Conclusions:

• Repeated kidney biopsies are essential for morphological and etiological reclassification in MPGN, with about half and one-third of patients benefiting, respectively.
• Stronger complement deposition may correlate with morphological changes observed in serial biopsies.
• Repeat kidney biopsies are critical for diagnosing MGRS, particularly in cases with initially negative immunofixation results, guiding targeted therapy.