Renal coloboma syndrome

Bilateral Morning Glory Anomaly With Optic Nerve Multiple Cysts

ABSTRACT

We herein describe a pediatric case of bilateral morning glory anomaly whose retrobulbar cysts and renal disease were underdiagnosed, and finally, he was diagnosed with renal coloboma syndrome. We recommend patients with colobomatous optic nerve malformations undergo a complete workup to avoid missed diagnosis, which includes (i) general physical examination looking for heart defects, genitourinary, auricular, and midline facial defects among other abnormalities; (ii) simple nephrologic investigations such as routine urine test and/or renal ultrasound to check for renal hypoplasia; and (iii) neuroimaging check for cerebrovascular anomalies and midline cranial defects. Genetic testing can be a useful tool to guide the workup.

Whole genome sequence analysis identifies a PAX2 mutation to establish a correct diagnosis for a syndromic form of hyperuricemia

Hereditary hyperuricemia may occur as part of a syndromic disorder or as an isolated nonsyndromic disease, and over 20 causative genes have been identified. Here, we report the use of whole genome sequencing (WGS) to establish a diagnosis in a family in which individuals were affected with gout, hyperuricemia associated with reduced fractional excretion of uric acid, chronic kidney disease (CKD), and secondary hyperparathyroidism, that are consistent with familial juvenile hyperuricemic nephropathy (FJHN). However, single gene testing had not detected mutations in the uromodulin (UMOD) or renin (REN) genes, which cause approximately 30-90% of FJHN. WGS was therefore undertaken, and this identified a heterozygous c.226G>C (p.Gly76Arg) missense variant in the paired box gene 2 (PAX2) gene, which co-segregated with renal tubulopathy in the family. PAX2 mutations are associated with renal coloboma syndrome (RCS), which is characterized by abnormalities in renal structure and function, and anomalies of the optic nerve. Ophthalmological examination in two adult brothers affected with hyperuricemia, gout, and CKD revealed the presence of optic disc pits, consistent with optic nerve coloboma, thereby revising the diagnosis from FJHN to RCS. Thus, our results demonstrate the utility of WGS analysis in establishing the correct diagnosis in disorders with multiple etiologies.

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.

Genetics of Vesicoureteral Reflux

Vesicoureteral reflux (VUR) is the retrograde passage of urine from the bladder to the upper urinary tract. It is the most common congenital urological anomaly affecting 1-2% of children and 30-40% of patients with urinary tract infections. VUR is a major risk factor for pyelonephritic scarring and chronic renal failure in children. It is the result of a shortened intravesical ureter with an enlarged or malpositioned ureteric orifice. An ectopic embryonal ureteric budding development is implicated in the pathogenesis of VUR, which is a complex genetic developmental disorder. Many genes are involved in the ureteric budding formation and subsequently in the urinary tract and kidney development. Previous studies demonstrate an heterogeneous genetic pattern of VUR. In fact no single major locus or gene for primary VUR has been identified. It is likely that different forms of VUR with different genetic determinantes are present. Moreover genetic studies of syndromes with associated VUR have revealed several possible candidate genes involved in the pathogenesis of VUR and related urinary tract malformations. Mutations in genes essential for urinary tract morphogenesis are linked to numerous congenital syndromes, and in most of those VUR is a feature. The Authors provide an overview of the developmental processes leading to the VUR. The different genes and signaling pathways controlling the embryonal urinary tract development are analyzed. A better understanding of VUR genetic bases could improve the management of this condition in children.

Heterozygous triplication of upstream regulatory sequences leads to dysregulation of matrix metalloproteinase 19 in patients with cavitary optic disc anomaly

Patients with a congenital optic nerve disease, cavitary optic disc anomaly (CODA), are born with profound excavation of the optic nerve resembling glaucoma. We previously mapped the gene that causes autosomal-dominant CODA in a large pedigree to a chromosome 12q locus. Using comparative genomic hybridization and quantitative PCR analysis of this pedigree, we report identifying a 6-Kbp heterozygous triplication upstream of the matrix metalloproteinase 19 (MMP19) gene, present in all 17 affected family members and no normal members. Moreover, the triplication was not detected in 78 control subjects or in the Database of Genomic Variants. We further detected the same 6-Kbp triplication in one of 24 unrelated CODA patients and in none of 172 glaucoma patients. Analysis with a Luciferase assay showed that the 6-Kbp sequence has transcription enhancer activity. A 773-bp fragment of the 6-Kbp DNA segment increased downstream gene expression eightfold, suggesting that triplication of this sequence may lead to dysregulation of the downstream gene, MMP19, in CODA patients. Lastly, immunohistochemical analysis of human donor eyes revealed strong expression of MMP19 in optic nerve head. These data strongly suggest that triplication of an enhancer may lead to overexpression of MMP19 in the optic nerve that causes CODA.

Association of PAX2 and Other Gene Mutations with the Clinical Manifestations of Renal Coloboma Syndrome

BACKGROUND

Renal coloboma syndrome (RCS) is characterized by renal anomalies and optic nerve colobomas. PAX2 mutations contribute to RCS. However, approximately half of the patients with RCS have no mutation in PAX2 gene.

METHODS

To investigate the incidence and effects of mutations of PAX2 and 25 candidate genes, patient genes were screened using next-generation sequence analysis, and candidate mutations were confirmed using Sanger sequencing. The correlation between mutations and clinical manifestation was evaluated.

RESULT

Thirty patients, including 26 patients (two families of five and two, 19 sporadic cases) with RCS, and 4 optic nerve coloboma only control cases were evaluated in the present study. Six PAX2 mutations in 21 probands [28%; two in family cohorts (n = 5 and n = 2) and in 4 out of 19 patients with sporadic disease] including four novel mutations were confirmed using Sanger sequencing. Moreover, four other sequence variants (CHD7, SALL4, KIF26B, and SIX4) were also confirmed, including a potentially pathogenic novel KIF26B mutation. Kidney function and proteinuria were more severe in patients with PAX2 mutations than in those without the mutation. Moreover, the coloboma score was significantly higher in patients with PAX2 gene mutations. Three out of five patients with PAX2 mutations had focal segmental glomerulosclerosis (FSGS) diagnosed from kidney biopsies.

CONCLUSION

The results of this study identify several new mutations of PAX2, and sequence variants in four additional genes, including a novel potentially pathogenic mutation in KIF26B, which may play a role in the pathogenesis of RCS.

Retinoschisis and outer retinal hole formation in a patient with papillorenal syndrome

This report describes a 19-year-old patient with the rare association of macular retinoschisis and outer retinal hole formation with papillorenal syndrome. Initially diagnosed with transplant-related central serous chorioretinopathy, she presented several years later with worsening vision and distortion in her right eye. On examination, she was found to have bilateral optic nerve dysplasia, bilateral macular and extramacular retinoschisis, and a serous retinal detachment with outer hole formation in the right eye. A history of prior renal transplantation due to poor kidney development led to the diagnosis of papillorenal syndrome.

Choroidal coloboma in a case of tay-sachs disease

Coloboma as an ocular finding has been documented in various syndromes. Here we have a case of infantile Tay-Sachs disease associated with unilateral choroidal coloboma. To the best of our knowledge, such an association has not been documented in the literature. Whether such an association is a matter of chance or signifies the involvement of ganglioside metabolism in ocular embryogenesis remains to be elucidated.

Systemic abnormalities in children with congenital optic disc excavations

PURPOSE

Together with optic disc hypoplasia, excavated optic disc anomalies represent the most frequent congenital abnormality involving the optic nerve head. The purpose of the present study was to retrospectively review the results of a screening for extraocular abnormalities in children presenting with congenital optic disc excavations.

MATERIALS AND METHODS

The medical records of 37 patients diagnosed with a unilateral or bilateral non glaucomatous optic disc excavation were retrospectively reviewed to analyze the result of the extra ocular evaluation and to report the associated ocular abnormalities.

RESULTS

An ocular abnormality was observed in conjunction with the excavated optic disc in 31% of the eyes. The systematic investigations revealed the presence of at least one extra-ocular disorder in 48% of the cases, and the optic disc excavation could be considered as syndromic in 30% of patients. The prevalence of extraocular malformations was significantly higher in infants presenting with associated ocular malformations or abnormal vision/development.

CONCLUSIONS

The present study suggests that a systematic approach to search for any associated systemic abnormalities could be envisioned in patients presenting with congenital excavated optic discs, and particularly those presenting with abnormal vision, associated ocular defects or abnormal development.

Congenital optic nerve anomaly and migration of subretinal oil: case report and observations in one family

PURPOSE

To describe a case of optic nerve (ON) anomaly and retinal detachment with extensive subretinal silicone oil after repair of retinal detachment. A three-generation family history of ON anomaly, two generations with detachment, is presented.

METHODS

Retrospective chart review. A multigenerational family with ON anomalies and macular detachment.

RESULTS

Final repair of retinal detachment was achieved using retinotomy for removal of subretinal 5,000-centistoke silicone oil, gas-fluid exchange, and peripapillary photocoagulation. Silicone oil had been previously used successfully in this eye, yet on subsequent use resulted in subretinal migration. A four patient-three-generation family history of ON anomalies was elicited, and three members were photographed for documentation.

CONCLUSION

Optic nerve anomalies and macular detachment present a treatment dilemma because they are associated with poor vision and often a suboptimal visual outcome after surgery. This case demonstrates a large amount of subretinal silicone oil, which migrated over a 2-month period. This case series is a report of a three-generational family demonstrating variable expressivity of ON anomalies complicated by macular detachment in two generations.

Peripheral nonperfusion and tractional retinal detachment associated with congenital optic nerve anomalies

PURPOSE

To report an association of congenital optic nerve anomalies with peripheral retina nonperfusion and to describe the clinical manifestations and treatment.

DESIGN

Retrospective, observational case series.

PARTICIPANTS

Fifteen patients with congenital optic nerve anomalies referred for pediatric retina consultation were studied. Sixteen eyes of 9 patients with optic nerve hypoplasia and 8 eyes of 6 patients with other congenital optic nerve anomalies, including optic nerve coloboma, morning glory disc, and peripapillary staphyloma, were included.

METHODS

All patients underwent examinations under anesthesia. Wide-angle retina photographs and fluorescein angiograms were reviewed. The severity of nonperfusion was graded. The presence of fibrovascular proliferation (FP), vitreous hemorrhage (VH), and tractional retinal detachment (TRD) were documented. Anatomic outcome after treatment was recorded.

MAIN OUTCOME MEASURES

Severity of nonperfusion, occurrence of secondary complications, and the anatomic outcome of patients who underwent laser treatment.

RESULTS

In patients with optic nerve hypoplasia, 12 of 16 eyes (75%) had severe peripheral nonperfusion, 12 of 16 eyes (75%) had FP, 3 of 16 eyes (19%) had VH, and 10 of 16 eyes (63%) had TRD. Six of these eyes with severe nonperfusion received laser photocoagulation to the nonperfused retina; laser-treated retinas remained attached in all 6 eyes. In patients with the other optic nerve anomalies, 7 of 8 eyes (88%) had mild to moderate nonperfusion, 2 of 8 eyes (25%) had FP, 1 of 8 eyes (12%) had VH, and 2 of 8 eyes (25%) had TRD. Six of 9 patients (67%) with optic nerve hypoplasia and 1 of 6 patients (17%) with other anomalies had a coexisting congenital brain disease.

CONCLUSIONS

Congenital optic nerve anomalies may be associated with peripheral retina nonperfusion and the secondary complications of FP, VH, and TRD. In this select group of patients, the nonperfusion associated with optic nerve hypoplasia seemed to be more severe and associated more frequently with secondary complications. Peripheral retina examination in eyes with optic nerve anomalies may identify nonperfusion or FP. Laser treatment of the avascular retina may have helped prevent complications from proliferative retinopathy in eyes clinically observed to have progressed or considered at risk for progression to proliferative retinopathy.

PAX2 in human kidney malformations and disease

Human PAX2 mutations have been associated with abnormalities in the developing and adult kidney ranging from congenital abnormalities of the kidney and urinary tract (CAKUT) to oncogenic processes. Defining the relationship of PAX2 to human renal disease requires an appreciation of its fundamental role in renal development. Given the highly conserved nature of the PAX2 gene in vertebrates, it is not surprising that much of our understanding of PAX2 involvement in renal disease has been derived from animal models. The following review will outline the current evidence supporting involvement of PAX2 in the pathologic processes involving the kidney.

Update of PAX2 mutations in renal coloboma syndrome and establishment of a locus-specific database

Renal coloboma syndrome, also known as papillorenal syndrome is an autosomal-dominant disorder characterized by ocular and renal malformations. Mutations in the paired-box gene, PAX2, have been identified in approximately half of individuals with classic findings of renal hypoplasia/dysplasia and abnormalities of the optic nerve. Prior to 2011, there was no actively maintained locus-specific database (LSDB) cataloguing the extent of genetic variation in the PAX2 gene and phenotypic variation in individuals with renal coloboma syndrome. Review of published cases and the collective diagnostic experience of three laboratories in the United States, France, and New Zealand identified 55 unique mutations in 173 individuals from 86 families. The three clinical laboratories participating in this collaboration contributed 28 novel variations in 68 individuals in 33 families, which represent a 50% increase in the number of variations, patients, and families published in the medical literature. An LSDB was created using the Leiden Open Variation Database platform: www.lovd.nl/PAX2. The most common findings reported in this series were abnormal renal structure or function (92% of individuals), ophthalmological abnormalities (77% of individuals), and hearing loss (7% of individuals). Additional clinical findings and genetic counseling implications are discussed.

A novel interstitial deletion of 10q24.2q24.32 in a patient with renal coloboma syndrome

Renal coloboma syndrome (RCS) is considered to be a rare autosomal dominant inherited disorder characterized by renal malformations and optic disc coloboma. Ocular anomalies range from asymptomatic abnormalities in retinal blood vessel patterning to large excavations of the optic nerve associated with reduced visual acuity. Commonly observed manifestations of the kidney are renal hypoplasia and vesicoureteric reflux leading to end-stage renal disease. Mutations in the PAX2 gene on chromosome 10 have been identified in patients with RCS. Up to date, nucleotide substitutions, insertions, small deletions, one de novo translocation, and one 240 kb deletion of the coding region of the PAX2 gene have been described to be responsible for RCS. We report here a new case of a patient with RCS due to a deletion of 3.8 Mb on chromosome 10q. Deletions on the long arm of chromosome 10 harboring the PAX2 gene seem to be a rare cause for RCS. Nevertheless, array-CGH testing should represent an important and valuable addition to PAX2 gene sequencing in diagnostic of RCS.

Genetics of vesicoureteral reflux

Primary vesicoureteral reflux (VUR) is the most common urological anomaly in children, affecting 1-2% of the pediatric population and 30-40% of children presenting with urinary tract infections (UTIs). Reflux-associated nephropathy is a major cause of childhood hypertension and chronic renal failure. The hereditary and familial nature of VUR is well recognized and several studies have reported that siblings of children with VUR have a higher incidence of reflux than the general pediatric population. Familial clustering of VUR implies that genetic factors have an important role in its pathogenesis, but no single major locus or gene for VUR has yet been identified and most researchers now acknowledge that VUR is genetically heterogeneous. Improvements in genome-scan techniques and continuously increasing knowledge of the genetic basis of VUR should help us to further understand its pathogenesis.

Renal coloboma syndrome

Renal coloboma syndrome (RCS), also called papillorenal syndrome, is an autosomal dominant condition characterized by optic nerve dysplasia and renal hypodysplasia. The eye anomalies consist of a wide and sometimes excavated dysplastic optic disc with the emergence of the retinal vessels from the periphery of the disc, frequently called optic nerve coloboma or morning glory anomaly. Associated findings may include a small corneal diameter, retinal coloboma, scleral staphyloma, optic nerve cyst and pigmentary macular dysplasia. The kidney abnormalities consist of small and abnormally formed kidneys known as renal hypodysplasia. Histologically, kidneys exhibit fewer than the normal number of glomeruli and these glomeruli are enlarged, a finding called oligomeganephronia. Consequences of the ocular malformations include decreased visual acuity and retinal detachment. Consequences of the renal hypodysplasia include hypertension, proteinuria and renal insufficiency that frequently progresses to end-stage kidney disease. High frequency hearing loss has been reported. Autosomal dominant mutations in PAX2 can be identified in nearly half of all patients with clinical findings suggestive of RCS, however, the majority of published cases have mutations in PAX2, thus biasing the known information about the phenotype.

Optic nerve abnormalities in children: a practical approach

Evaluation of children with optic nerve abnormalities is challenging. Fundus photography, ocular coherence tomography, visual field testing, color vision evaluation, neuroimaging, and genetic testing are helpful in the diagnosis and management of these patients. Importantly, many optic nerve problems are not isolated but occur in association with systemic and central nervous system anomalies. The ophthalmologist thus plays a critical role in recognizing patients who warrant systemic and neurologic assessment.

Retinal detachment in morning glory syndrome with large hole in the excavated disc

PURPOSE

To present a case of morning glory syndrome (MGS) associated with retinal detachment and to discuss the pathogenesis of retinal tear.

METHODS

A 2-year-old-girl had a MGS with a large hole in the excavated disc and retinal detachment. The visual acuity was 4/200 in the affected eye. The excavated disc and retinal detachment were confirmed by echogram. Optical coherence tomography demonstrated that the large hole was connected to the subretinal space. The excavated lesion did not show contractions. The detachment area and the volume of subretinal fluid rose and fell between initial examinations, but ultimately increased. After 2 years of observations, surgery was performed as the retinal detachment had enlarged to include the macula.

RESULTS

Surgery included triamcinolone-assisted vitrectomy, subretinal fluid drainage through the large hole in the excavated disc, retinal photocoagulation along the excavated disc, and long-acting gas tamponade. One month later, the retina was redetached due to incomplete closure of the hole. A second operation was performed using silicone oil tamponade. Ultimately, the retina was reattached after silicone oil-fluid exchange surgery.

CONCLUSIONS

One possible reason for a large hole in an excavated disc is origination of the tear from a congenital defect, such as an optic pit. The retinal detachment in patients with MGS with a large hole in the disc can be treated with triamcinolone-assisted pars plana vitrectomy and retinal photocoagulation along the excavated disc. This case has shown that one critical component for a high success rate is the tamponade agent used in the vitreous.

PAX2 mutations in fetal renal hypodysplasia

Papillorenal syndrome also known as renal-coloboma syndrome (OMIM 120330) is an autosomal dominant condition comprising optic nerve anomaly and renal oligomeganephronic hypoplasia. This reduced number of nephron generations with compensatory glomerular hypertrophy leads towards chronic insufficiency with renal failure. We report on two fetuses with PAX2 mutations presenting at 24 and 18 weeks' gestation, respectively, born into two different sibships. In our first patient, termination of pregnancy was elected for anhydramnios and suspicion of renal agenesis in the healthy couple with an unremarkable previous clinical history. This fetus had bilateral asymmetric kidney anomalies including a small multicystic left kidney, and an extremely hypoplastic right kidney. Histology showed dysplastic lesions in the left kidney, contrasting with rather normal organization in the hypoplastic right kidney. Ocular examination disclosed bilateral optic nerve coloboma. The association of these anomalies, highly suggestive of the papillorenal syndrome, led us to perform the molecular study of the PAX2 gene. Direct sequencing of the PAX2 coding sequence identified a de novo single G deletion of nucleotide 935 in exon 3 of the PAX2 resulting in a frameshift mutation (c.392delG, p.Ser131Thrfs*28). In the second family, the presence of a maternally inherited PAX2 mutation led to a decision for termination of pregnancy. The 18-week gestation fetus presented the papillorenal syndrome including hypoplastic kidneys and optic nerve coloboma. In order to address the PAX2 involvement in isolated renal "disease," 18 fetuses fulfilling criteria were screened: 10/18 had uni- or bilateral agenesis, 6/18 had bilateral multicystic dysplasia with enlarged kidneys, and 2/18 presented bilateral severe hypodysplasia confirmed on fetopathological examination. To the best of our knowledge, our first patient represents an unreported fetal diagnosis of papillorenal syndrome, and another example of the impact of oriented fetopathological examination in genetic counseling of the parents.

Papillorenal syndrome-causing missense mutations in PAX2/Pax2 result in hypomorphic alleles in mouse and human

Papillorenal syndrome (PRS, also known as renal-coloboma syndrome) is an autosomal dominant disease characterized by potentially-blinding congenital optic nerve excavation and congenital kidney abnormalities. Many patients with PRS have mutations in the paired box transcription factor gene, PAX2. Although most mutations in PAX2 are predicted to result in complete loss of one allele's function, three missense mutations have been reported, raising the possibility that more subtle alterations in PAX2 function may be disease-causing. To date, the molecular behaviors of these mutations have not been explored. We describe a novel mouse model of PRS due to a missense mutation in a highly-conserved threonine residue in the paired domain of Pax2 (p.T74A) that recapitulates the ocular and kidney findings of patients. This mutation is in the Pax2 paired domain at the same location as two human missense mutations. We show that all three missense mutations disrupt potentially critical hydrogen bonds in atomic models and result in reduced Pax2 transactivation, but do not affect nuclear localization, steady state mRNA levels, or the ability of Pax2 to bind its DNA consensus sequence. Moreover, these mutations show reduced steady-state levels of Pax2 protein in vitro and (for p.T74A) in vivo, likely by reducing protein stability. These results suggest that hypomorphic alleles of PAX2/Pax2 can lead to significant disease in humans and mice.

Congenital ocular malformations affecting the optic nerve are an important cause of childhood blindness. The papillorenal syndrome (PRS) is an autosomal dominant disorder that causes congenital optic nerve and kidney abnormalities, which may result in legal blindness and renal failure, respectively. Many cases of PRS are caused by mutations in the paired-box transcription factor PAX2. In this paper, we describe a novel mouse model of this human disease caused by a missense mutation in the Pax2 gene at the same position of one of the few disease-causing missense mutations in humans. We characterize the ocular and non-ocular phenotypes of this mouse and model the effect that murine and human Pax2/PAX2 mutations have on protein structure. We also experimentally test the effect these missense mutations have on protein localization, transactivation, and DNA binding, concluding that all three reduce steady-state levels of protein in vitro and (in p.T74A) in vivo by reducing protein stability. This work will help us better understand the pathophysiology of PRS and to dissect the molecular interactions important in normal PAX2 function.

Renal malformations associated with mutations of developmental genes: messages from the clinic

Renal tract malformations (RTMs) account for about 40% of children with end-stage renal failure. RTMs can be caused by mutations of genes normally active in the developing kidney and lower renal tract. Moreover, some RTMs occur in the context of multi-organ malformation syndromes. For these reasons, and because genetic testing is becoming more widely available, pediatric nephrologists should work closely with clinical geneticists to make genetic diagnoses in children with RTMs, followed by appropriate family counseling. Here we highlight families with renal cysts and diabetes, renal coloboma and Fraser syndromes, and a child with microdeletion of chromosome 19q who had a rare combination of malformations. Such diagnoses provide families with often long-sought answers to the question "why was our child born with kidney disease". Precise genetic diagnoses will also help to define cohorts of children with RTMs for long-term clinical outcome studies.

Simultaneous presentation of retinoblastoma and morning glory disk anomaly

PURPOSE

To describe a patient with retinoblastoma and morning glory disk anomaly (MGDA).

METHOD

Observational case report.

RESULTS

A 7-month-old girl with bilateral retinoblastoma was found to have concurrent MGDA in the less involved eye. The more severely affected eye was enucleated due to progressive disease not amenable to aggressive systemic and local treatment; histologic analysis was performed.

CONCLUSION

Prompt ocular examination of a pediatric patient should be performed in the presence of concerning findings such as leukokoria or strabismus. In addition, more than one ocular abnormality may coexist, such as retinoblastoma and MGDA, necessitating complete examination.

Optic nerve dysplasia and renal insufficiency in a family with a novel PAX2 mutation, Arg115X: further ophthalmologic delineation of the renal-coloboma syndrome

Renal-coloboma syndrome, an autosomal dominant disorder associated with mutations in PAX2, is characterized by colobomatous eye defects, renal hypoplasia, vesicoureteral reflux, high-frequency hearing loss, and rarely central nervous system abnormalities. We identified a three-generation family with optic nerve colobomatous dysplasia and renal disease. We report the identification of a novel mutation in PAX2 in this family with renal-coloboma syndrome, Arg115X. We also report on the ocular and extraocular manifestations of PAX2 mutations for all cases of renal-coloboma syndrome reported to date.

Bilateral macular detachment caused by bilateral optic nerve malformation in a papillorenal syndrome due to a new PAX2 mutation

PURPOSE

Papillorenal syndrome is an autosomal dominant entity due to PAX2 gene mutation, involving optic nerve and renal malformations.

METHODS

The authors report a 19-year-old man with bilateral macular detachment associated with optic nerve pit in one eye and morning glory syndrome in the other eye. The patient underwent three-port pars plana vitrectomy, endolaser photocoagulation, and C3F8 gas tamponade in his best eye. A medical history of vesicoureteric reflux and kidney hypoplasia led to genetic analysis.

RESULTS

Molecular genetic PAX2 analysis revealed a novel nondescribed mutation in exon 3. One year postoperatively, ophthalmologic outcomes were satisfactory with complete flattening of the retina and improvement of the best-corrected visual acuity to 11/10.

CONCLUSIONS

PAX2 is involved in the optic vesicles, genital tracts, kidney, and central nervous system embryogenic development. The association of optic nerve and renal malformations should lead to the suspicion of papillorenal syndrome with PAX2 mutation.

Optic nerve axon number in mouse is regulated by PAX2

BACKGROUND

Papillorenal syndrome is an autosomal-dominant disease caused by mutations in the PAX2 transcription factor gene. Patients often exhibit congenital excavation of the optic nerve and a spectrum of congenital kidney abnormalities. Using a novel mouse model of this syndrome (C57BL/6J PAX2(A220G/+)), we investigated the effect of PAX2 haploinsufficiency on optic nerve axon number. Because PAX2 expression and retinal pigment epithelium pigmentation have a mutually exclusive relationship during development and because tyrosinase (Tyr) has been shown to modify the penetrance of other ocular development genes, we also investigated whether tyrosinase modified the mutant PAX2 phenotype.

METHODS

C57BL/6J PAX2(A220G/+)Tyr(+/+) mice were crossed with mice of the same genetic background (C57BL/6J) that are homozygous for an effective null allele of tyrosinase (Tyr(c-2J/c-2J)) over two generations to create mice with four distinct genotypes: PAX2(A220G/+) Tyr(+/c-2J), PAX2(A220G/+) Tyr(c-2J/c-2J), PAX2(+/+) Tyr(c-2J/+), and PAX2(+/+)Tyr(c-2J/c-2J). Mouse optic nerves were examined clinically and histologically. Axon number was assessed in a masked fashion in optic nerves from mice of all four genotypes and compared with parental strains.

RESULTS

Mice heterozygous for a PAX2 mutation show reduced optic nerve axon number compared with age-matched controls. Tyrosinase does not appear to modify this phenotype.

CONCLUSIONS

Our results show that PAX2 is important in determining axon number in mouse optic nerve. The developmental effects of tyrosinase and PAX2 mutation appear to act via different pathways.

A clinico-genetic study of renal coloboma syndrome in children

Renal coloboma syndrome (RCS) is an autosomal dominant disorder caused by PAX2 gene mutations and characterized by renal hypoplasia and optic disc coloboma. The clinical findings were retrospectively reviewed, and all coding regions of the PAX2 gene were sequenced, in six children with RCS. A c.619_620insG mutation was detected in five patients, including two siblings, and a novel p.Arg104X mutation was detected in one patient. All the patients had progressive renal dysfunction and bilateral hypoplastic kidneys without vesicoureteral reflux (VUR), but the rate of progression to end-stage renal disease showed some diversity. The ocular manifestations showed wide variability, ranging from subtle optic disc anomalies to microphthalmia. In one family with two affected siblings, maternal germline mosaicism was suggested by an intragenic microsatellite marker study. In conclusion, there are variable renal and ocular manifestations in RCS without significant phenotype-genotype correlations. VUR is not a cardinal renal manifestation of RCS. The possibility of germline mosaicism should be considered during molecular diagnosis and genetic counseling for PAX2 mutations.

Familial cavitary optic disk anomalies: clinical features of a large family with examples of progressive optic nerve head cupping

PURPOSE

To describe a multigenerational family with autosomal dominant inheritance of cavitary optic nerve head (ONH) anomalies and abnormal ONH vasculature.

DESIGN

Description of a single family with inherited eye disease.

METHODS

A four-generation pedigree was investigated. Examination included visual acuity, slit-lamp biomicroscopy, intraocular pressure (IOP) measurement, and ophthalmoscopy. Visual fields and fundus photography were obtained when possible.

RESULTS

Seventeen clinically affected individuals and two obligate carriers were identified. Most (64.7%) affected persons had bilateral involvement. Visual acuity in affected eyes ranged from 20/20 to no light perception. Although the appearance of affected nerves varied greatly, most lacked a well-formed central retinal artery and instead had multiple radial cilioretinal arteries. Prominent cupping was seen in most affected nerves. Four individuals for whom information was available were treated for glaucoma, but none had documented elevated IOP. Four eyes of two patients demonstrated progressive ONH cupping at normal IOPs. Nine (56.3%) of the 16 individuals for whom we had data had evidence of serous macular detachments; five of these had bilateral macular disease.

CONCLUSIONS

A large family with autosomal dominant inheritance of cavitary ONH anomalies and abnormal vasculature is presented. Clinical phenotypes varied markedly. Progressive ONH cupping was documented in four eyes of two patients. Genetic linkage analysis of this family has identified the chromosomal location of a gene responsible for ONH development. This may provide insight into the pathogenesis of glaucomatous ONH damage.

Chiari Type І Malformation Associated With Morning Glory Disc Anomaly

Morning glory disc anomaly (MGDA) is a congenital malformation of the optic disc that has been reported in association with midline craniofacial defects such as basal encephalocele, hypertelorism, cleft lip and palate, and agenesis of the corpus callosum. We describe a 44 year-old woman with MGDA and Chiari type capital I, Ukrainian malformation, an association not previously reported.

Uveal coloboma: clinical and basic science update

PURPOSE OF REVIEW

To integrate knowledge on the embryologic and molecular basis of optic fissure closure with clinical observations in patients with uveal coloboma.

RECENT FINDINGS

Closure of the optic fissure has been well characterized and many genetic alterations have been associated with coloboma; however, molecular mechanisms leading to coloboma remain largely unknown. In the past decade, we have gained better understanding of genes critical to eye development; however, mutations in these genes have been found in few individuals with coloboma. CHD7 mutations have been identified in patients with CHARGE syndrome (coloboma, heart defects, choanal atresia, retarded growth, genital anomalies, and ear anomalies or deafness). Animal models are bringing us closer to a molecular understanding of optic fissure closure.

SUMMARY

Optic fissure closure requires precise orchestration in timing and apposition of two poles of the optic cup. The relative roles of genetics and environment on this process remain elusive. While most cases of coloboma are sporadic, autosomal dominant, autosomal recessive, and X-linked inheritance patterns have been described. Genetically, colobomata demonstrate pleiotropy, heterogeneity, variable expressivity, and reduced penetrance. Coloboma is a complex disorder with a variable prognosis and requires regular examination to optimize visual acuity and to monitor for potential complications.

Optic disc pit: primary diagnosis in a child

Congenital abnormalities of the optic nerve head are commonly detected by optometrists in practice. While some severe abnormalities can lead to poor visual acuity and are associated with other ocular and systemic disorders, others such as pits of the optic disc are predominantly benign with a latent risk of visual loss. This report details the primary diagnosis of unilateral optic disc pit in a seven-year-old patient.

Alagille syndrome and optic pit

BACKGROUND

Optic disc anomalies are frequently associated with Alagille syndrome. We report here the first case of a patient with Alagille syndrome combined with optic pit and serous macular detachment.

METHODS

A male patient with Alagille syndrome was referred from the pediatric hepatology department for investigation of visual loss in the right eye. Anterior segment examination showed evidence of posterior embryotoxon, confirmed by gonioscopic evaluation. Dilated fundus examination revealed serous macular detachment and optic pit.

RESULTS

OCT 3 scans confirmed the clinical findings.

CONCLUSIONS

Optic pit is uncommon and should prompt a search for genetic disorders or development abnormalities. The association between the two syndromes in this patient might be due to failure of correct neuroectodermal development, for which a common genetic pathway is likely.

Potential role of Pax-2 in retinal axon navigation through the chick optic nerve stalk and optic chiasm

The degree of fiber decussation at the optic chiasm differs between species, ranging from complete crossing in lower vertebrates to highly complex patterns of intermingling of the fibers from the two eyes seen in mammals and birds. Understanding the genetic control of fiber guidance through the chiasm is therefore important to unravel the developmental mechanisms within the visual system. Here we first report on early stages of chiasm formation, with pioneering axons from the left eye consistently arriving earlier than their counterparts from the right eye. This initial left-right asymmetry is transient and no functional significance is assigned to it yet. Secondly, we examined formation of the chiasm in relation with the expression of the transcription factor Pax-2 along the ventral eye cup and optic nerve stalk. Finally, in order to examine causal involvement of Pax-2 in chiasm formation, the gene was overexpressed along the neuraxis and in the eye cup at embryonic stages preceding the exit of axons from the eye, and hence arrival of axons at the chiasm. When studied with neuroanatomical tracing, Pax-2 overexpression resulted in visibly anomalous decussation of axons at the chiasm. A likely consequence of this perturbation was erroneous arrival of axons at the tectum, as observed by anterograde staining from the retina. These data suggest that balanced expression of Pax-2 results in the correct formation of the chick chiasm at early stages by imposing accurate pathfinding within the optic stalk and the midline.