Clinical and Renal Histology Findings and Different Responses to Induction Treatment Affecting the Long-Term Renal Outcomes of Children With ANCA-Associated Vasculitis: a Single-Center Cohort Analysis.

Introduction: Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is relatively rare in children. This article aimed to analyze clinical and renal histology findings and different responses to induction treatment associated with the long-term renal outcomes in children with AAV in a single center. Methods: All pediatric patients with AAV admitted to Tongji Hospital from January 2002 to January 2021 were included in the study. The demographic, clinical, pathological, laboratory, and treatment data and outcomes were collected and analyzed to identify predictors associated with response to induction treatment and progression to end-stage renal disease (ESRD). Results: In total, 48 children with AAV were included in this cohort; 81.25% of them were women, and 91.7% were microscopic polyangiitis (MPA). Kidney involvement was found in 45 patients (93.75%). The most common histopathological subtype was crescentic form in this cohort according to Berden's classification. In total, 34 patients (70.8%) showed eGFR <60 ml/min/1.73 m2 at the time of diagnosis. Complete and partial remission was achieved in 8 patients (16.7%) and 19 patients (39.6%), respectively, following 6-month induction treatment. Half of the patients eventually progressed to ESRD at a mean time of (13.04 ± 15.83) months after diagnosis. The independent predictors of nonremission following induction treatment and progression to ESRD were baseline eGFR <60 ml/min/1.73 m2 and hypertension at diagnosis. Renal survival significantly decreased over time in patients with renal sclerotic subtypes or those with nonremission following induction treatment by Kaplan-Meier curve estimation. Conclusions: Our study demonstrates that women, MPA, and crescentic subtypes are predominant in pediatric AAV in China. Initial renal failure (eGFR <60 ml/min/1.73 m2), hypertension, sclerotic pathological subtype, and nonremission following induction treatment are predictive of long-term renal outcomes.

CUBN gene mutations may cause focal segmental glomerulosclerosis (FSGS) in children.

BACKGROUND: Imerslund-Gräsbeck Syndrome (IGS) is mainly caused by CUBN gene biallelic mutations. Proteinuria accompanies IGS specific symptoms in about half of the patients, isolated proteinuria is rarely reported. Here we present 3 patients with isolated proteinuria and focal segmental glomerulosclerosis (FSGS) caused by CUBN gene biallelic pathogenic variants. METHOD: Whole exome sequencing was performed on three children with isolated proteinuria. CUBN gene biallelic pathogenic variants were found and then verified by sanger sequencing. Their clinical, pathological and molecular genetic characteristics were analyzed and correlated accordingly. RESULTS: All three children presented with isolated proteinuria, no megaloblastic anemia. Their urine levels of ß2 microglobulin were normal or slightly higher. Renal biopsies showed focal segmental glomerulosclerosis with mild glomerular mesangial hypercellularity, partial effacement of foot processes and podocyte microvillation. Two of them were found to carry compound heterozygous mutations and one homozygous mutation of CUBN gene. Totally four CUBN gene biallelic pathogenic variants were identified, including c.9287 T > C (p.L3096P), c.122 + 1G > A, c.7906C > T (p.R2636*), c.10233G > A (p.W3411*). Except for intron splice-site mutation, all other variants are located in highly conserved sites of CUB domain for binding to albumin. CONCLUSION: The results demonstrate that CUBN gene mutations may cause isolated proteinuria pathologically presented as FSGS. Our cases extend the spectrum of renal manifestation and genotype of CUBN gene mutations.

A Presumed Synonymous Mutation of PKD2 Caused Autosomal Dominant Polycystic Kidney Disease in a Chinese Family.

OBJECTIVE: Autosomal dominant polycystic kidney disease (ADPKD) is mainly caused by the pathogenic mutation of PKD1 or PKD2 gene and usually affects bilateral kidneys. Synonymous mutations are generally assumed to be neutral as they do not alter amino acids. Herein, we described an extremely rare ADPKD child caused by a heterozygous synonymous mutation of PKD2 gene accompanied by massive proteinuria and congenital solitary kidney. METHODS: Clinical characteristics of the patients were summarized. Whole-exome sequencing was performed to screen the disease-causing gene mutation, and reverse transcription polymerase chain reaction (RT-PCR) and Sanger sequencing were applied to analyze the impact of the identified mutation on gene transcription and splicing. RESULTS: Polycystic changes were found in the solitary kidney of a girl initially presented with nephrotic-range proteinuria. Thereafter her mother and 2 other family members were diagnosed to be ADPKD. Whole-exome sequencing of the proband identified a heterozygous synonymous mutation (c.1716G>A, p.Lys572=) located in the splicing site of exon 7 in PKD2 gene, which was co-segregated with the PKD phenotype in the family. RT-PCR and direct sequencing of amplified products revealed that this heterozygous synonymous mutation led to exon7 skipping in PKD2 gene. CONCLUSION: We reported an extremely rare child case of ADPKD2 in combination with solitary kidney and nephrotic-range proteinuria, and firstly confirmed the pathogenicity of a heterozygous synonymous mutation (c.1716G>A) in PKD2 gene. The results indicate that synonymous mutations should not be excluded from disease-causing if they are located in splicing site of an exon.