Diverse Renal Phenotypes Observed in a Single Family with a Genetic Mutation in Paired Box Protein 2

Ocular manifestations of the genetic causes of focal and segmental glomerulosclerosis

Genetic forms of focal and segmental glomerulosclerosis (FSGS) often have extra-renal manifestations. This study examined FSGS-associated genes from the Genomics England Renal proteinuria panel for reported and likely ocular features. Thirty-two of the 55 genes (58%) were associated with ocular abnormalities in human disease, and a further 12 (22%) were expressed in the retina or had an eye phenotype in mouse models. The commonest genes affected in congenital nephrotic syndrome (NPHS1, NPHS2, WT1, LAMB2, PAX2 but not PLCE1) may have ocular manifestations . Many genes affected in childhood-adolescent onset FSGS (NPHS1, NPHS2, WT1, LAMB2, SMARCAL1, NUP107 but not TRPC6 or PLCE1) have ocular features. The commonest genes affected in adult-onset FSGS (COL4A3-COL4A5, GLA ) have ocular abnormalities but not the other frequently affected genes (ACTN4, CD2AP, INF2, TRPC6). Common ocular associations of genetic FSGS include cataract, myopia, strabismus, ptosis and retinal atrophy. Mitochondrial forms of FSGS (MELAS, MIDD, Kearn's Sayre disease) are associated with retinal atrophy and inherited retinal degeneration. Some genetic kidney diseases (CAKUT, ciliopathies, tubulopathies) that result in secondary forms of FSGS also have ocular features. Ocular manifestations suggest a genetic basis for FSGS, often help identify the affected gene, and prompt genetic testing. In general, ocular abnormalities require early evaluation by an ophthalmologist, and sometimes, monitoring or treatment to improve vision or prevent visual loss from complications. In addition, the patient should be examined for other syndromic features and first degree family members assessed.

Diagnostic Yield and Benefits of Whole Exome Sequencing in CAKUT Patients Diagnosed in the First Thousand Days of Life

Introduction

Congenital anomalies of the kidney and urinary tract (CAKUT) are the predominant cause of chronic kidney disease (CKD) and the need for kidney replacement therapy (KRT) in children. Although more than 60 genes are known to cause CAKUT if mutated, genetic etiology is detected, on average, in only 16% of unselected CAKUT cases, making genetic testing unproductive.

Methods

Whole exome sequencing (WES) was performed in 100 patients with CAKUT diagnosed in the first 1000 days of life with CKD stages 1 to 5D/T. Variants in 58 established CAKUT-associated genes were extracted, classified according to the American College of Medical Genetics and Genomics guidelines, and their translational value was assessed.

Results

In 25% of these mostly sporadic patients with CAKUT, a rare likely pathogenic or pathogenic variant was identified in 1 or 2 of 15 CAKUT-associated genes, including GATA3, HNF1B, LIFR, PAX2, SALL1, and TBC1D1. Of the 27 variants detected, 52% were loss-of-function and 18.5% de novo variants. The diagnostic yield was significantly higher in patients requiring KRT before 3 years of age (43%, odds ratio 2.95) and in patients with extrarenal features (41%, odds ratio 3.5) compared with patients lacking these criteria. Considering that all affected genes were previously associated with extrarenal complications, including treatable conditions, such as diabetes, hyperuricemia, hypomagnesemia, and hypoparathyroidism, the genetic diagnosis allowed preventive measures and/or early treatment in 25% of patients.

Conclusion

WES offers significant advantages for the diagnosis and management of patients with CAKUT diagnosed before 3 years of age, especially in patients who require KRT or have extrarenal anomalies.

PAX2 Gene Mutation in Pediatric Renal Disorders-A Narrative Review

The PAX2 gene is a transcription factor that is essential for the development of the urinary system among other transcription factors. The role of PAX2 is highlighted from the seventh week of gestation, when it is involved in development processes and the emergence of nephrons and collecting tubes. Being an important factor in renal development, mutations of this gene can produce severe alterations in the development of the urinary tract, namely congenital anomalies of the kidneys and urinary tract. The first reported cases described with the PAX2 mutation included both renal anomalies and the involvement of other organs, such as the eyes, producing renal coloboma syndrome. Over the years, numerous cases have been reported, including those with only renal and urinary tract anomalies. The aim of this review is to present a summary of pediatric patients described to have mutations in the PAX2 gene to contribute to a better understanding of the genetic mechanism causing anomalies of the kidneys and urinary tract. In this review, we have included only pediatric cases with renal and urinary tract disorders, without the involvement of other organs. From what we know so far from the literature, this is the first review gathering pediatric patients presenting the PAX2 mutation who have been diagnosed exclusively with renal and urinary tract disorders.

Papillorenal syndrome: a systemic diagnosis not to be missed on funduscopy

A 45-year-old man presented to the ophthalmology department with visual symptoms in his left eye. Almost two decades ago, he required a renal transplant for focal segmental glomerular sclerosis and a detailed enquiry revealed a strong family history of renal and ocular disease. Fundus examination demonstrated significant optic disc dysplasia in his left eye and optical coherence tomography showed intraretinal fluid bilaterally. The diagnosis of papillorenal syndrome was suspected and genetic testing identified a heterozygous pathogenic variant in the PAX2 gene c.76dupG, p.Val26Glyfs*28, confirming the diagnosis. The patient was treated conservatively, and his vision eventually improved and stabilised. His renal disease and transplant were concurrently monitored by nephrologists. In this case, history-taking and ophthalmic examination raised suspicion of this rare systemic condition, which led to genetic testing and molecular confirmation of the diagnosis. We therefore highlight this case to raise awareness of papillorenal syndrome, which has significant systemic implications and also impacts familial screening and genetic counselling.

A novel PAX2 heterozygous mutation in a family with Papillorenal syndrome: A case report and review of the literature

Purpose

Papillorenal syndrome (PAPRS) is a rare inherited disorder often involves abnormalities of eye and kidney. Paired box 2 (PAX2) gene, which is widely expressed in the development of the organs including kidney, ureter, eye, ear, and central nervous system has been considered an underlying cause of PAPRS. The present work aims to further our understanding of PAX2 gene and PAPRS by reporting a family with PAPRS associated with a novel PAX2 mutation and describing ocular manifestation of PAX2 mutation in previous literatures.

Observation

We herein present a family with PAPRS presented with typical congenital optic disc defects and mild renal dysplasia. Through screening of candidate genes based on the next-generation sequencing, the heterozygous PAX2 mutation c.175C > T (p. Arg59Trp) was identified which had never been reported.

Conclusions

The study expands the genetic and clinic spectrum of PAPRS. Further review of detailed ocular manifestation and genotypes of PAX2 mutation in previous study improves the recognition of the ocular phenotypes' spectrum, assists in the identification of PAPRS. Moreover, this study reveals that PAPRS is a systemic disorder with heterogeneous diverse phenotypes, and shows the importance of gene panel sequencing in the diagnosis of PAPRS which could achieve high diagnostic rates.

PAX2 Mutation-Related Renal Hypodysplasia: Review of the Literature and Three Case Reports

Paired box 2 (PAX2)-related disorder is an autosomal dominant genetic disorder associated with kidney and eye abnormalities and can result in end stage renal disease (ESRD). Despite reported low prevalence of PAX2 mutations, the prevalence of PAX2 related disorders may have been underestimated in past studies. With improved genetic sequencing techniques, more genetic abnormalities are being detected than ever before. Here, we report three patients from two families with PAX2 mutations identified within 1 year. Two patients were adults with chronic kidney disease and were followed for decades without correct diagnoses, including one with ESRD who had even undergone kidney transplant. The third patient was a neonate in whom PAX2-related disorder manifested as oligohydramnios, coloboma, and renal failure that progressed to ESRD within 1 year after birth. The phenotypes of PAX2 gene mutation were shown to be highly variable, even within the same family. Early detection promoted genetic counseling and guided clinical management. The appropriate time point for genetic study is an important issue. Clinicians must be more alert for PAX2 mutation when facing patients with congenital kidney and urinary tract anomalies, chronic kidney disease of unknown etiology, involvement of multiple systems, and/or a family history of renal disease.

PAX2 Mutation-Related Oligomeganephronia in a Young Adult Patient

Oligomeganephronic hypoplasia, commonly referred to as oligomeganephronia (OMN), is a rare pediatric disorder characterized by small kidneys. Histologically a paucity of nephrons is observed which show compensatory enlargement. Hyperfiltration injury leads to end-stage kidney disease. Here we report a 23-year-old Caucasian female patient who presented with a 7-year history of nonnephrotic proteinuria, slow worsening of renal function, normal-sized kidneys, normal blood pressure, healthy weight, and normoglycemia. Evaluation of a kidney biopsy specimen revealed sparsely distributed and markedly enlarged glomeruli (glomerular density 0.63/mm², glomerular diameter 268 µm), focal segmental glomerulosclerosis (FSGS), and 70% effacement of the foot processes. The glomerular basement membrane was normal (mean thickness 285 nm). The genetic analysis of 19 genes known to cause FSGS identified a heterozygous de novo nonsense mutation of PAX2 in exon 4 (NM_003990.3:c.430C>T and NP_003981.2:p.Gln144Ter). Clinical investigations ruled out optic nerve coloboma, hearing loss, and vesicoureteral reflux. Magnetic resonance imaging of the urogenital tract found the uterus to be bicornuate. Based on these data, OMN in nonhypoplastic kidneys and adaptive FSGS related to PAX2 mutation was diagnosed. Her kidney function worsened during the 30-month follow-up (last visit: eGFR-EPI 32 mL/min/1.73 m²) despite angiotensin-converting enzyme inhibitor treatment. To our best knowledge, our patient is the seventh in the English-language literature with a biopsy diagnosis of OMN in an adult, the first observed with normal-sized kidneys, and the first in whom a specific etiologic genetic diagnosis was established. Nonsense PAX2 mutations between the paired domain and the octapeptide domain appear to manifest in renal-limited phenotype.

Clinical and genetic variability of PAX2-related disorder in the Japanese population

Pathogenic variants of paired box gene 2 (PAX2) cause autosomal-dominant PAX2-related disorder, which includes renal coloboma syndrome (RCS). Patients with PAX2-related disorder present with renal and ophthalmological pathologies, as well as with other abnormalities, including developmental problems and hearing loss. We sequenced PAX2 in 457 patients with congenital anomalies of the kidney and urinary tract or with renal dysfunction of unknown cause and identified 19 different pathogenic variants in 38 patients from 30 families (6.5%). Thirty-four patients had renal hypodysplasia or chronic kidney disease of unknown cause, and three had focal segmental glomerulosclerosis. Although no obvious genotype-phenotype correlation was observed, six of the seven patients who developed end-stage renal disease in childhood had truncating variants. Twenty-three patients had ocular disabilities, mostly optic disc coloboma. Non-renal and non-ophthalmological manifestations included developmental disorder, electrolyte abnormality, and gonadal abnormalities. Two unrelated patients had congenital cystic adenomatoid malformations in their lungs. Six of ten probands with PAX2 mutation identified by next-generation sequencing did not show typical RCS manifestations. We conclude that PAX2-related disorder has a variable clinical presentation and can be diagnosed by next-generation sequencing even in the absence of typical RCS manifestations.

Diverse phenotypes in children with PAX2-related disorder

BACKGROUND

The aim of this study was to analyze the diverse phenotypes of children with PAX2-related disorder so as to improve our understanding of this disease.

METHODS

The clinical data of ten children with PAX2 mutations, detected by targeted region capture sequencing or whole-exome sequencing, were retrospectively analyzed. Family members of index cases were verified by Sanger sequencing and family segregation analysis was performed.

RESULTS

The age of first symptom of 10 unrelated children (six girls and four boys) was 6.4 (ranged from postnatal day to 14.8) years old. Proteinuria, abnormal renal function, and structure were found in all patients. Renal hypoplasia and renal cysts were found in 10 of 10 and five of 10 cases, respectively. Three patients progressed to chronic kidney disease stage 5 and the onset age of end-stage renal disease was 9.8-16.4 years old. PAX2-related ocular abnormalities were found in five of seven cases and three patients were observed to have more than one ocular findings involved. In addition to diverse renal and ocular findings, new phenotypes including congenital ventricular septal defect, skeletal deformity (fourth metatarsal microsomia), ovarian teratoma, and relatively rare extrarenal manifestations such as growth retardation, gout, and microcephaly were also found. Three novel mutations were reported for the first time. De novo mutations occurred in all patients who were carried out segregation analysis. Patients with the same mutation had different manifestations. PAX2-related disorder showed remarkable clinical variability and phenotypic heterogeneity.

CONCLUSION

We firstly reported skeletal deformity (fourth metatarsal microsomia), ovarian teratoma, and congenital ventricular septal defect as new phenotypes of PAX2-related disorder which enlarged the phenotypic spectrum. Gout was firstly reported as the onset symptom of PAX2-related disorder. The diagnosis of PAX2-related disorder should be considered without family history due to a much higher percentage of De novo mutations.

New PAX2 heterozygous mutation in a child with chronic kidney disease: a case report and review of the literature

BACKGROUND

We herein report a 3-year-old boy presented with chronic kidney disease (CKD) due to PAX2 missense mutation (C to G transversion at position 418 in exon 4).

CASE PRESENTATION

He attended our clinic with a 3-month history of foamy urine. Upon examination, he had reduced estimated glomerular filtration rate (GFR) and renal atrophy. Genetic investigations revealed that he has inherited a mutated PAX2 gene from his father, who had renal failure at the age of 20. We searched the literature and confirmed that this mutation site has not been reported by any other group before.

CONCLUSIONS

Although renal coloboma syndrome (RCS) with simultaneous kidney and eye involvement is the most common phenotype of PAX2 mutations, current literature supports that such mutations may have profuse clinical manifestations and renal hypoplasia is one distinct entity in the spectrum.