Elisa Buti

Podocytopathies represent a group of glomerular disorders associated with minimal changes (MC) or focal segmental glomerulosclerosis (FSGS) lesion patterns at biopsy and heterogeneous responses to steroids. Anti-nephrin antibodies were previously found in such patients, suggesting an autoimmune form of podocytopathy. High resolution confocal microscopy on kidney biopsies of a cohort of 128 pediatric patients revealed localization of IgG along the slit diaphragm in 30% of patients with MC and 25% of those with FSGS, but not in other lesion patterns. Anti-nephrin IgG ELISA assay in the serum and stimulated emission depletion microscopy of kidney biopsies showed IgG-nephrin co-localization only in 77.8% of cases. Similar observations were obtained in a cohort of 48 adult patients with MC or FSGS at kidney biopsy, where IgG-nephrin colocalization was only 44.4%, suggesting the existence of autoantibodies binding to other slit proteins. Patients with anti-slit antibodies showed nephrotic syndrome at onset in 94.4% of cases. Patients with primary steroid-resistance had anti-slit antibodies in 27%, while those with secondary steroid-resistance in 87.5% of cases, irrespective of the histopathological lesion pattern. Steroid-resistant patients with anti-slit antibodies responded to second-line immunosuppressants in 92.3% vs. only 20% of patients that were anti-slit negative. No patient with anti-slit antibodies developed kidney failure vs. 51.7% of those negative for antibodies (66.7% with a genetic cause and 41.2% with a non-genetic cause). Thus, the detection of anti-slit antibodies can identify patients with an autoimmune podocytopathy responsive to treatment with second-line immunosuppressants, irrespective of the histopathological lesion pattern at biopsy.

Noninvasive tools for diagnosis or prediction of acute kidney allograft rejection have been extensively investigated in recent years. Biochemical and molecular analyses of blood and urine provide a liquid biopsy that could offer new possibilities for rejection prevention, monitoring, and therefore, treatment. Nevertheless, these tools are not yet available for routine use in clinical practice. In this systematic review, MEDLINE was searched for articles assessing urinary biomarkers for diagnosis or prediction of kidney allograft acute rejection published in the last five years (from January 1, 2015 to May 31, 2020). This review follows the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines. Articles providing targeted or unbiased urine sample analysis for the diagnosis or prediction of both acute cellular and antibody-mediated kidney allograft rejection were included, analyzed, and graded for methodological quality with a particular focus on study design and diagnostic test accuracy measures. Urinary C-X-C motif chemokine ligands were the most promising and frequently studied biomarkers. The combination of precise diagnostic reference in training sets with accurate validation in real-life cohorts provided the most relevant results and exciting groundwork for future studies.

Erdheim-Chester disease (ECD) is a rare histiocytic disorder that can present as a localized infiltration of foamy histiocytes or a multisystem disease that may be life-threatening. It is extremely rare in children. Pegoraro and colleagues present the clinical and molecular features of 21 patients with pediatric ECD through a large international collaboration, documenting that it resembles its adult counterpart, with similar molecular features and responses to agents targeting BRAF and MEK.

BACKGROUND: The reliability of kidney biopsy as the sole means for assessing kidneys from extended-criteria donors (ECDs) to be allocated to single or dual transplantation is still a matter of debate. METHODS: We compared retrospectively 3 years graft survival and renal function in 44 recipients of a single kidney graft from a marginal donor with good renal function and a Karpinski histological score of ≤ 3 and 56 recipients of a single transplant with a Karpinski score of 4 or 5. The donors' and recipients' characteristics were compared by means of Wilcoxon's rank-sum test and Fisher's exact test, and survival was analysed using the log-rank test and Cox regression survival analysis. RESULTS: The donors with the worse histological scores were slightly younger (68.0 ± 4.74 versus 71.3 ± 4.6 years, P < 0.01) and had a higher glomerular filtration rate (85.8 ± 28.2 versus 76.3 ± 26.53 mL/min, P = 0.013), but there was no difference in serum creatinine levels (0.83 ± 0.24 versus 0.85 ± 0.30 mg/dL, P = 0.381). Three years after transplantation, there was no difference between the two groups in terms of recipient serum creatinine levels (1.94 ± 0.69 versus 1.74 ± 0.49 mg/dL, P = 0.134), estimated glomerular filtration rate (eGFR, 45.6 ± 21.1 versus 51.7 ± 22.0 mL/min, P = 0.331) or the rates of graft loss (27.3 versus 35.7%, P = 0.47), delayed graft function or acute rejection. CONCLUSIONS: In our experience, provided the donor has a normal renal function, a difference in the pre-transplant histological score of kidneys from marginal cadaveric donors do not have a significant influence on the outcome 3 years after transplantation. Our findings might represent a basis for designing a randomized controlled trial of using a higher histological score threshold for the DKT allocation of grafts from ECDs with a normal renal function.