Search

Background: In nephrotic range proteinuria of adult-onset, kidney biopsy is the diagnostic gold standard in determining the underlying cause of disease. However, in low grade or subnephrotic proteinuria the diagnostic value of kidney biopsy as first-line diagnostics is less well established., Methods: We conducted a retrospective analysis of all native kidney biopsies at our institution (n = 639) between 01/2012 and 05/2021 for comparison of histological diagnoses and clinical outcomes stratified by amount of proteinuria at the time of kidney biopsy: A: <300mg/g creatinine (low grade), B: 300-3500mg/g creatinine (subnephrotic), C >3500mg/g creatinine (nephrotic)., Results: Nephrotic range proteinuria was associated with the highest frequency (49.3%) of primary glomerulopathies followed by subnephrotic (34.4%) and low grade proteinuria (37.7%). However, within the subnephrotic group, the amount of proteinuria at kidney biopsy was linearly associated with renal and overall survival (HR 1.05 per Δ100mg protein/g creatinine (95% CI: 1.02-1.09, p = 0.001)) independent of present histological diagnoses and erythrocyturia., Conclusion: Frequency of primary glomerulopathies supports to perform kidney biopsy in patients with subnephrotic proteinuria. These patients have a substantial risk of ESKD and death upon follow-up. Therefore, diagnostic accuracy including histopathology is essential to guide personalized treatment and avert detrimental courses., Competing Interests: The authors have declared that no competing interests exist.

Background: Patients on renal replacement therapy are often unaware of their underlying condition and hence suffer from so-called end-stage renal disease (ESRD) of unknown origin. However, an exact diagnosis is not only important for better estimating the prognosis, but also when preparing for kidney transplantation. Whilst patients with FSGS without a confirmed genetic cause have a high recurrence rate in the transplanted organ, patients with a mutation generally exhibit no recurrence and have a good prognosis. Furthermore, renal biopsy, which may be helpful for differential diagnosis, is usually contraindicated in end-stage kidneys. We here present the case of familial ESRD of unknown origin, which could be resolved by targeted genetic testing prior to planning of kidney transplantation. Case presentation: A 32-year-old female with ESRD and nephrotic range proteinuria was admitted to our clinic. Family-history revealed that both mother and maternal grandmother had ESRD of unknown origin. As renal biopsy was impossible due to atrophic kidneys, we performed mutation analysis of genes known for dominant forms of FSGS and found a novel heterozygous mutation of INF2 (c.485 T > C, p.Leu162Pro). The same mutation could be detected in the index patient’s mother (ESRD at age 50) and three brothers with normal serum-creatinine but mid or low range proteinuria. Conclusions: Genetic testing is warranted in families with ESRD of unknown origin and may provide a robust diagnosis even without kidney biopsy. It will help detecting relatives at risk who have to be excluded from potential kidney donation and who may benefit from timely initiation of protective measures in order to slow down disease progression. [ABSTRACT FROM AUTHOR]