Abstract
Immunoglobulin M nephropathy (IgMN) is an idiopathic glomerulonephritis characterized by diffuse deposits of IgM in the glomerular mesangium. However, its renal prognosis remains unknown. We compared renal outcomes of IgMN patients with those of patients with minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), or mesangial proliferative glomerulonephritis (MsPGN) from a prospective observational cohort, with 1791 patients undergoing native kidney biopsy in eight hospitals affiliated with The Catholic University of Korea between December 2014 and October 2020. IgMN had more mesangial proliferation and matrix expansion than MsPGN and more tubular atrophy and interstitial fibrosis than MCD. IgMN patients had decreased eGFR than MCD patients in the earlier follow-up. However, there was no significant difference in urine protein or eGFR among all patients at the last follow-up. When IgMN was divided into three subtypes, patients with FSGS-like IgMN tended to have lower eGFR than those with MCD-like or MsPGN-like IgMN but higher proteinuria than MsPGN-like IgMN without showing a significant difference. The presence of hypertension at the time of kidney biopsy predicted ≥20% decline of eGFR over two years in IgMN patients. Our data indicate that IgMN would have a clinical course and renal prognosis similar to MCD, FSGS, and MsPGN.
Highlights
Since the first description of Immunoglobulin M (IgM) nephropathy (IgMN) in the 1970s [1,2,3], there has still been controversy about the independence of Immunoglobulin M nephropathy (IgMN) in the range of glomerular diseases [3,4]
We evaluated whether there could be differences in clinical and pathological characteristics according to variable LM findings of IgMN, such as minimal change disease (MCD)-like, focal segmental glomerulosclerosis (FSGS)-like, and mesangial proliferative glomerulonephritis (MsPGN)-like IgMN, and what factors could influence the renal outcome of IgMN
The prevalence of IgMN in this cohort was 5.2%. (n = 94) As shown in Table 1, the mean age at kidney biopsy was older in the FSGS group than in the MsPGN group (p = 0.016)
Summary
Since the first description of Immunoglobulin M (IgM) nephropathy (IgMN) in the 1970s [1,2,3], there has still been controversy about the independence of IgMN in the range of glomerular diseases [3,4]. Light microscopy has demonstrated various histological pictures, ranging from no glomerular abnormality to mesangial hyperplasia and accumulation of the extracellular mesangial matrix of varying degrees, associated with segmental or global sclerosis of the glomeruli [3,4,5,6,7]. Because of these varying morphological characteristics, IgMN as an independent entity has been questioned [4]. There are still arguments about the definitive diagnosis and methods to identify and classify IgM nephropathy before a global and robust consensus is reached
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