title: The natural history of immunoglobulin M nephropathy in adults.
abstract: BACKGROUND
  Immunoglobulin M (IgM) nephropathy is an idiopathic glomerulonephritis characterized by diffuse mesangial deposition of IgM. IgM nephropathy has been a controversial diagnosis since it was first reported, and there are few data identifying specific pathological features that predict the risk of progression of renal disease.
  
  
  METHODS
  We identified 57 cases of IgM nephropathy among 3220 adults undergoing renal biopsy at our institution. Biopsies had to satisfy the following three criteria to meet the definition of IgM nephropathy in this study: (i) dominant mesangial staining for IgM, (ii) mesangial deposits on electron microscopy (EM) and (iii) exclusion of systemic disease.
  
  
  RESULTS
  The median age was 42 years and 24 patients were male. Thirty-nine per cent of patients presented with the nephrotic syndrome, 49% presented with non-nephrotic proteinuria and 39% had eGFR <60 mL/min. The median post-biopsy follow-up was 40 months and serum creatinine had doubled in 31% by 5 years. Of histological parameters, glomerular sclerosis and tubular atrophy, but not mesangial proliferation, were risk factors for renal insufficiency. Thirty-nine per cent of nephrotic patients achieved complete remission, and outcome was significantly worse in those who did not respond to treatment. Focal segmental glomerulosclerosis was diagnosed in 80% of those undergoing repeat renal biopsy, despite ongoing mesangial IgM deposition.
  
  
  CONCLUSIONS
  We propose criteria for a consensus definition of IgM nephropathy.
authors.affiliation: Renal and Vascular Inflammation Section, Department of Medicine, Imperial College London, London W12 0NN, UK.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Connor
authors.affiliation: Department of Nephrology, Policlinico S.Orsola-Malpighi, Università di Bologna, Bologna, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Aiello
authors.affiliation: Renal and Vascular Inflammation Section, Department of Medicine, Imperial College London, London W12 0NN, UK.
authors.forename: Megan
authors.initials: M
authors.lastname: Griffith
authors.affiliation: Renal and Vascular Inflammation Section, Department of Medicine, Imperial College London, London W12 0NN, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Cairns
authors.affiliation: Renal and Vascular Inflammation Section, Department of Medicine, Imperial College London, London W12 0NN, UK.
authors.forename: Candice A
authors.initials: CA
authors.lastname: Roufosse
authors.affiliation: Centre for Complement and Inflammation Research, Department of Medicine, Imperial College London, London, UK.
authors.forename: H Terence
authors.initials: HT
authors.lastname: Cook
authors.affiliation: Renal and Vascular Inflammation Section, Department of Medicine, Imperial College London, London W12 0NN, UK.
authors.forename: Charles D
authors.initials: CD
authors.lastname: Pusey
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D005260:Female; D005920:Glomerular Mesangium / Q000378:metabolism / Q000473:pathology*; D005921:Glomerulonephritis / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D007075:Immunoglobulin M / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009404:Nephrotic Syndrome / Q000378:metabolism / Q000473:pathology*; D011507:Proteinuria / Q000209:etiology; D012189:Retrospective Studies; D012307:Risk Factors; D055815:Young Adult
chemical_list: D007075:Immunoglobulin M
keywords: glomerulonephritis; immunoglobulin M; nephrotic syndrome; outcome; renal biopsy