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Membranoproliferative glomerulonephritis (MPGN) is a rare chronic nephropathy, affecting predominantly children and young adults and defined by a typical glomerular histopathological pattern of mesangial hypercellularity, endocapillary proliferation and duplication of the glomerular basement membrane. While clinical presentation and outcome are variable, the overall prognosis is poor, with progression to end-stage renal disease (ESRD) in about 40% of cases.
The aim of the present work was to study the natural history of primary MPGN and to explore the relationship between proteinuria at one year after diagnosis and renal outcome.
Subjects with a histological diagnosis of MPGN were selected from the Italian Registry of MPGN. Secondary forms were excluded.
Parameters were collected at disease onset, at baseline (defined as the time of the first diagnostic biopsy), at 1-year follow-up (with an accepted range of 6 to 18 months) and at the last available follow-up. ESRD was defined by either an estimated glomerular filtration rate (eGFR) below 15 ml/min/1.73m2, dialysis initiation or preemptive kidney transplantation.
For the primary analysis, we excluded subjects with:
- Follow-up < 6 months after baseline
- ESRD before baseline or < 6 months thereafter
- Complement inhibition initiation < 6 months after baseline
- Missing 24h-proteinuria data at 1-year follow-up
- Missing eGFR at last available follow-up
The primary outcome was the correlation between 24h-proteinuria at one year after baseline and eGFR at last follow-up. eGFR in subjects in dialysis was considered 15 ml/min/1.73m2.
Table 1a and 1b: full cohort description
In conclusion, this study on patients with idiopathic MPGN selected from the Italian Registry of MPGN demonstrated a negative correlation between quantitative proteinuria at one year and long-term renal function. These findings support the possibility of considering proteinuria reduction as a predictor of long-term renal outcome.