IgA Nephropathy Follow-up

Updated: Oct 11, 2017
  • Author: Mona Brake, MD; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Follow-up

Prognosis

Although IgA nephropathy usually follows a benign course, end-stage renal disease (ESRD) develops in 15-20% of patients within 10 years of onset and in about 25-30% of patients by 20 years. However, these observations are obtained from biopsy-proven disease and do not include patients with isolated hematuria, who typically do not have a biopsy performed and have a good prognosis.

The Oxford classification of IgA nephropathy, published in 2009, comprises four histological features that are independent predictors of clinical outcome. [2] The four features determine the MEST score, as follows:

  • M – Mesengial cellularity, defined as more than four mesangial cells in any mesangial area of a glomerulus: M0 is mesangial cellularity in <50% of glomeruli; M1 is mesangial cellularity in ≥50%
  • E – Endocapillary proliferation, defined as hypercellularity due to an increased number of cells within glomerular capillary lumina: E0 is absence of hypercellularity; E1 is hypercellularity in any glomeruli
  • S – Segmental glomerulosclerosis, defined as adhesion or sclerosis (obliteration of capillary lumina by matrix) in part but not the whole glomerular tuft: S0 is absence of segmental glomerulosclerosis, S1 is presence of segmental glomerulosclerosis in any glomerulus
  • T – Tubular atrophy/interstitial fibrosis, defined as estimated percentage of cortical area showing tubular atrophy or interstitial fibrosis, whichever is greater: T0 is 0-25%; T1 is 25-50%; T2 is >50%

Subsequent studies validated the predictive utility of the M, S, and T features, with the T score consistently proving the most significant predictor of poor renal outcomes. However, E lesions are predictive of outcome only in patients without immunosuppression. [10] In 2017, the working group that produced the Oxford classification recommended adding glomerular crescents to the MEST score (MEST-C). [34]

Haas et al reported that the presence of crescents in one sixth of glomeruli was associated with a hazard ratio of 1.63 for a ≥50% decline in estimated glomerular filtration rate (eGFR) or ESRD; the hazard ratio rose to 2.29 in patients with crescents in at least one fourth of glomeruli. However, until crescents were found in over one fourth of glomeruli, the increased risk applied only in patients who were not immunosuppressed. [35] These authors propose the following crescent scores:

  • C0 – No crescents
  • C1 – Crescents in less than one fourth of glomeruli; if not receiving immunosuppression, these patients are at increased risk of poor outcome
  • C2 – Crescents in over one fourth of glomeruli; these patients are at greater risk of progression, even if they are receiving immunosuppression

In a 2012 study in 141 white patients with biopsy-proven IgA nephropathy who presented with normal renal function, microscopic hematuria, and minimal or no proteinuria, the long-term prognosis was excellent. Such patients are not often biopsied, so the study served to validate the Oxford classification criteria at the benign end of the spectrum. The study was conducted in a European population, suggesting that genetic factors play a role in IgA prognosis, as studies of Asian groups with a similar "benign" presention  have reported a worse prognosis. [36]

In a study of 1155 Chinese patients with IgA nephropathy, the long-term prognosis was significantly better in patients presenting with recurrent macroscopic hematuria than in those with isolated macroscopic hematuria or no history of macroscopic hematuria. The 20-year cumulative renal survival after biopsy for the three groups was 91%, 64%, and 57%, respectively. [37]

IgA nephropathy is characterized by a highly variable clinical course. Many efforts have been made to determine clinical and histological features associated with progression to ESRD, as follows [38, 39] :

  • Clinically, patients with microscopic hematuria tend to have a higher risk than those with macroscopic hematuria. This phenomenon could be due to the ability to identify patients with gross hematuria at an earlier stage of disease. Sustained hypertension, impaired renal function, persistent hematuria, and proteinuria above 1 g/d are also poor prognostic markers.
  • Prolonged proteinuria is the strongest predictor of the rate of renal function decline. Patients who achieve a partial or complete remission of proteinuria do better than patients who never achieve a remission. [40]
  • A study published in 2002 by Italian investigators showed a worse prognosis for patients with familial IgA nephropathy, as compared with sporadic IgA nephropathy. [41]
  • In IgA nephropathy, as in an ever-increasing spectrum of renal disease, fibroblast growth factor–23 (FGF23) is a marker for disease progression and worse prognosis. [42]
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