Co-existence of thin basement membrane nephropathy with other glomerular pathologies; a single center experience

Background: The co-existence of thin basement membrane nephropathy (TBMN) and another glomerular pathology portends a worse prognosis than TBMN alone. Objectives: The purpose of our study was to investigate the prevalence of TBMN and associated glomerular pathologies at our institution. Patients and Methods: We reviewed all renal biopsies performed at Saint Louis University hospital over a 7-year period. We excluded all post transplant biopsies, and biopsies showing diabetic glomerulopathy, membranoproliferative glomerulopathy, membranous glomerulopathy, and biopsies where no electron microscopy or immunofluorescent studies were done. All other biopsies were included. Results: A total of 634 biopsies were included in the study. The prevalence of TBMN was 47 (7.4%), of whom 17 (36.2%) had TBMN alone. In the remaining 30 (63.8%) patients TBMN was associated with other glomerular pathologies: IgAN 9 (19.1%) and FSGS 9 (19.1%). We found significantly higher prevalence of IgAN in patients with TBMN versus all biopsies (19.1% vs. 7.7%, respectively, P = 0.002). We found significant similarities in biopsy indications for TBMN and IgAN group. Conclusions: Around two thirds of the cases of TBMN were associated with other glomerular pathologies. The prevalence of IgAN, but not focal segmental glomerulosclerosis, was significantly higher in patients with TBMN as compared to the general renal biopsy specimens.