Ophthalmic features of CHARGE syndrome with CHD7 mutations

Ocular manifestations of congenital anomalies of the kidney and urinary tract (CAKUT)

Congenital anomalies of the kidney and urinary tract (CAKUT) are among the most common birth defects worldwide and a major cause of kidney failure in children. Extra-renal manifestations are also common. This study reviewed diseases associated with the Genomics England CAKUT-associated gene panel for ocular anomalies. In addition, each gene was examined for expression in the human retina and an ocular phenotype in mouse models using the Human Protein Atlas and Mouse Genome Informatics databases, respectively. Thirty-four (54%) of the 63 CAKUT-associated genes (55 'green' and 8 'amber') had a reported ocular phenotype. Five of the 6 most common CAKUT-associated genes (PAX2, EYA1, SALL1, GATA3, PBX1) that represent 30% of all diagnoses had ocular features. The ocular abnormalities found with most CAKUT-associated genes and with five of the six commonest were coloboma, microphthalmia, optic disc anomalies, refraction errors (astigmatism, myopia, and hypermetropia), and cataract. Seven of the CAKUT-associated genes studied (11%) had no reported ocular features but were expressed in the human retina or had an ocular phenotype in a mouse model, which suggested further possibly-unrecognised abnormalities. About one third of CAKUT-associated genes (18, 29%) had no ocular associations and were not expressed in the retina, and the corresponding mouse models had no ocular phenotype. Ocular abnormalities in individuals with CAKUT suggest a genetic basis for the disease and sometimes indicate the affected gene. Individuals with CAKUT often have ocular abnormalities and may require an ophthalmic review, monitoring, and treatment to preserve vision.

Inherited causes of combined vision and hearing loss: clinical features and molecular genetics

Combined vision and hearing loss, also known as dual sensory impairment, can occur in several genetic conditions, including ciliopathies such as Usher and Bardet-Biedl syndrome, mitochondrial DNA disorders and systemic diseases, such as CHARGE, Stickler, Waardenburg, Alport and Alstrom syndrome. The retinal phenotype may point to the diagnosis of such disorders. Herein, we aim to provide a comprehensive review of the molecular genetics and clinical features of the most common non-chromosomal inherited disorders to cause dual sensory impairment.

Clinical spectrum of orbital and ocular abnormalities on fetal MRI

BACKGROUND

Fetal magnetic resonance imaging (MRI) may reveal sonographically occult ocular abnormalities. When discovered, acquired causes and genetic associations must be sought.

OBJECTIVE

We aim to evaluate a fetal cohort with orbit and/or globe malformations to determine whether there are imaging patterns that suggest the underlying cause.

MATERIALS AND METHODS

We searched all fetal MRI reports performed at an academic children's hospital over 9 consecutive years for orbit and/or globe abnormalities. Each positive exam and all follow-up MRIs were evaluated for interocular distance, globe size, shape and signal, and brain malformations. Genetic and clinical diagnoses were recorded from the medical record.

RESULTS

Seventy-six of 3,085 fetuses (2.5%) were diagnosed with ocular and/or globe abnormalities; 50% had postnatal follow-up MR exams, all confirming the fetal MRI findings. Ninety-two percent (70/76) had concurrent brain malformations. Sixty-seven percent (51/76) were diagnosed with an underlying disorder and 39% of these were genetically proven. The most common diagnoses with ocular globe abnormalities included CHARGE (coloboma of the eye, heart anomaly, choanal atresia, retardation and genital and ear anomalies) syndrome, trisomy 13 syndrome, dystroglycanopathy, holoprosencephaly and diencephalic-mesencephalic junction dysplasia. Genetic diagnoses were more likely with ocular globe abnormalities than isolated orbital abnormalities (P=0.04). Sixty-seven percent of fetuses with ocular calcifications, hemorrhage and/or lens abnormalities had potential maternal risk factors (P=0.03).

CONCLUSION

Malformed ocular globes are associated with brain malformations and genetic abnormalities. Ocular calcifications, hemorrhage and/or lens abnormalities may be associated with maternal risk factors. Genetic work-up should be considered when an ocular globe size or shape abnormality is detected.

Eyes on CHARGE syndrome: Roles of CHD7 in ocular development

The development of the vertebrate visual system involves complex morphogenetic interactions of cells derived from multiple embryonic lineages. Disruptions in this process are associated with structural birth defects such as microphthalmia, anophthalmia, and coloboma (collectively referred to as MAC), and inherited retinal degenerative diseases such as retinitis pigmentosa and allied dystrophies. MAC and retinal degeneration are also observed in systemic congenital malformation syndromes. One important example is CHARGE syndrome, a genetic disorder characterized by coloboma, heart defects, choanal atresia, growth retardation, genital abnormalities, and ear abnormalities. Mutations in the gene encoding Chromodomain helicase DNA binding protein 7 (CHD7) cause the majority of CHARGE syndrome cases. However, the pathogenetic mechanisms that connect loss of CHD7 to the ocular complications observed in CHARGE syndrome have not been identified. In this review, we provide a general overview of ocular development and congenital disorders affecting the eye. This is followed by a comprehensive description of CHARGE syndrome, including discussion of the spectrum of ocular defects that have been described in this disorder. In addition, we discuss the current knowledge of CHD7 function and focus on its contributions to the development of ocular structures. Finally, we discuss outstanding gaps in our knowledge of the role of CHD7 in eye formation, and propose avenues of investigation to further our understanding of how CHD7 activity regulates ocular and retinal development.

CHARGE Syndrome Associated with Ocular Abnormalities: A Case Report with Treatment of Amblyopia and Refractive Correction

CHARGE syndrome is a rare genetic disorder associated with many ocular anomalies including amblyopia, strabismus and high refractive errors. It has been found that the visual acuity of patients with CHARGE syndrome is typically lower than 20/60. After reviewing the literature, there has been a lack of detailed information about the assessments of visual function. Thus, this case report illustrates the strategy plan to treat amblyopia and refractive correction for a young girl with CHARGE syndrome.

Visual Function and Ophthalmological Findings in CHARGE Syndrome: Revision of Literature, Definition of a New Clinical Spectrum and Genotype Phenotype Correlation

CHARGE syndrome (CS) is a rare genetic disease causing multiple anatomical defects and sensory impairment. Visual function is usually reported by caregivers and has never been described with a structured behavioral assessment. Our primary objective was to describe ocular abnormalities, visual function and genotype–ocular-phenotype correlation in CS. A prospective monocentric cohort study was performed on 14 children with CS carrying pathogenic CHD7 variants. All children underwent ophthalmological evaluation and structured behavioral assessment of visual function. The VISIOCHARGE questionnaire was administered to parents. Colobomas were present in 93% of patients. Genotype–phenotype correlation documented mitigated features in a subset of patients with intronic pathogenic variants predicted to affect transcript processing, and severe features in patients with frameshift/nonsense variants predicting protein truncation at the N-terminus. Abnormal visual function was present in all subjects, with different degrees of impairment. A significant correlation was found between visual function and age at assessment (p-value = 0.025). The present data are the first to characterize visual function in CS patients. They suggest that hypomorphic variants might be associated with milder features, and that visual function appears to be related to age. While studies with larger cohorts are required for confirmation, our data indicate that experience appears to influence everyday use of visual function more than ocular abnormalities do.

Biallelic CDK9 variants as a cause of a new multiple-malformation syndrome with retinal dystrophy mimicking the CHARGE syndrome

CDK9 has been considered a candidate gene involved in the CHARGE-like syndrome in a pair of cousins. We report an 8-year-old boy with a strikingly similar phenotype including facial asymmetry, microtia with preauricular tags and bilateral hearing loss, cleft lip and palate, cardiac dysrhythmia, and undescended testes. Joint contracture, no finger flexion creases, and large halluces were the same as those of a previously reported patient with homozygous CDK9 variants. The ocular phenotype included blepharophimosis, lacrimal duct obstruction, eyelid dermoids, Duane syndrome-like abduction deficit, and congenital cataracts. Optical coherence tomography and electroretinography evaluations revealed severe retinal dystrophy had developed at an early age. Trio-based whole-exome sequencing identified compound heterozygous variants in CDK9 [p.(A288T) of maternal origin and p.(R303C) of paternal origin] in the patient. Variants’ kinase activities were reduced compared with wild type. We concluded that CDK9 biallelic variants cause a CHARGE-like malformation syndrome with retinal dystrophy as a distinguishing feature.

Dark-adapted threshold and electroretinogram for diagnosis of Usher syndrome

PURPOSE

To determine the utility of ophthalmology evaluation, dark-adapted threshold, and full-field electroretinogram for early detection of Usher syndrome in young patients with bilateral sensorineural hearing loss.

METHODS

We identified 39 patients with secure genetic diagnoses of Usher Syndrome. Visual acuity, spherical equivalent, fundus appearance, dark-adapted threshold, and full-field electroretinogram results were summarized and compared to those in a group of healthy controls with normal hearing. In those Usher patients with repeated measures, regression analysis was done to evaluate for change in visual acuity and dark-adapted threshold with age. Spherical equivalent and full-field electroretinogram responses from dark- and light-adapted eyes were evaluated as a function of age.

RESULTS

The majority of initial visual acuity and spherical equivalent results were within normal limits for age. Visual acuity and dark-adapted threshold worsened significantly with age in Usher type 1 but not in Usher type 2. At initial test, full-field electroretinogram responses from dark- and light-adapted eyes were abnormal in 53% of patients. Remarkably, nearly half of our patients (17% of Usher type 1 and 30% of Usher type 2) would have been missed by tests of retinal function alone if evaluated before age 10.

CONCLUSIONS

Although there is an association of abnormal dark-adapted threshold and full-field electroretinogram at young ages in Usher patients, it appears that a small but important proportion of patients would not be detected by tests of retinal function alone. Thus, genetic testing is needed to secure a diagnosis of Usher syndrome.

CHARGE syndrome without colobomas: Ophthalmic findings

To report ophthalmic findings of patients without colobomas, and with a clinical and molecular diagnosis of CHARGE Syndrome. Retrospective study of ophthalmic findings in 67 CHARGE patients-clinically confirmed diagnosis with positive CHD7 mutation-seen in the Ophthalmology department of Cincinnati Children's Hospital Medical Center between January 1, 2008 through September 25, 2018. Criteria for inclusion in this study was absence of any form of a coloboma in either eye. In our cohort, all patients had a positive CHD7 mutation, in addition to a clinical diagnosis. 19.4% (13/67) of CHARGE patients did not have a coloboma in either eye. 69.2% (9/13) had strabismus, 76.9% (10/13) had a refractive error that warranted refractive correction, 23.1% (3/13) had amblyopia, 38.5% (5/13) had nasolacrimal duct obstruction, 30.8% (4/13) had dry eye syndrome and exposure keratopathy, 15.4% (2/13) had ptosis, 15.4% (2/13) had blepharitis, 15.4% (2/13) had Cortical Visual Impairment, 7.7% (1/13) of patients had optic nerve drusen, 7.7% (1/13) had Marcus Gunn Jaw Winking, and 7.7% (1/13) with an eyelid nevus. There are numerous ophthalmic findings in individuals with CHARGE Syndrome without colobomas. No study to date has evaluated the ophthalmic findings in CHD7 positive CHARGE patients without colobomas. These findings need to be assessed and treated to ensure optimal vision in the CHARGE patient population. Absence of coloboma does not rule out a diagnosis of CHARGE syndrome, and if there is a clinical suspicion, clinical confirmation then genetic testing would be warranted.

Functional Vision Analysis in Patients With CHARGE Syndrome

PURPOSE

To evaluate functional vision in patients with CHARGE syndrome (coloboma, heart defects, atresia of the choanae, retardation of growth and development, genital and urinary anomalies, and ear anomalies) by using a new questionnaire entitled VISIOCHARGE.

METHODS

Ophthalmological data including fundus description and visual acuity, when available, were extracted from the charts of 83 patients with CHARGE syndrome, and the VISIOCHARGE questionnaire was prospectively mailed to 55 of those patients. The answers from the 36 responders (18 males) allowed for the calculation of three scores that assessed distance vision, near vision, and overall ability scores.

RESULTS

Visual acuity measurements were extracted from the charts of 20 of the 36 patients. The mean visual acuity was 20/50. The mean distance vision score of 0.62 ± 0.30 and near vision score of 0.78 ± 0.23 were correlated with visual acuity in the 20 patients (ρ = 0.64, P = .002 and ρ = 0.61, P = .005, respectively) and were associated with the severity of colobomatous malformation (P = .049 and P = .008, respectively). Severity of the ocular malformation was not associated with the overall ability score (P = .64).

CONCLUSIONS

The VISIOCHARGE questionnaire is feasible for patients with CHARGE syndrome and may help in the assessment of visual function. The mean visual acuity and answers to the VISIOCHARGE questionnaire showed relatively good visual skills in patients with CHARGE syndrome in everyday life, even in those with bilateral colobomas, which contrasts with the pessimistic conclusions usually resulting from the initial fundus examination. [J Pediatr Ophthalmol Strabismus. 2020;57(2):120-128.].

Genetics of syndromic ocular coloboma: CHARGE and COACH syndromes

Optic fissure closure defects result in uveal coloboma, a potentially blinding condition affecting between 0.5 and 2.6 per 10,000 births that may cause up to 10% of childhood blindness. Uveal coloboma is on a phenotypic continuum with microphthalmia (small eye) and anophthalmia (primordial/no ocular tissue), the so-called MAC spectrum. This review gives a brief overview of the developmental biology behind coloboma and its clinical presentation/spectrum. Special attention will be given to two prominent, syndromic forms of coloboma, namely, CHARGE (Coloboma, Heart defect, Atresia choanae, Retarded growth and development, Genital hypoplasia, and Ear anomalies/deafness) and COACH (Cerebellar vermis hypoplasia, Oligophrenia, Ataxia, Coloboma, and Hepatic fibrosis) syndromes. Approaches employed to identify genes involved in optic fissure closure in animal models and recent advances in live imaging of zebrafish eye development are also discussed.

CHARGE Syndrome Associated with Angle Closure despite High Myopia: A Case Report with Structural Suggestion

CHARGE syndrome is associated with multiple malformations, and the main ocular abnormality is coloboma. We describe an unusual case of a 15-year-old girl with CHARGE syndrome having high intraocular pressure and narrow angle closure despite refractive high myopia (−9.0 dpt) in her left eye. Gonioscopy revealed peripheral anterior synechia (approximately 90°) in the superior quadrant of the left eye. Both eyes exhibited similar axial length (about 22 mm) and corneal curvature (about 8 mm). However, microcornea (9 mm), thicker central cornea and iris induced narrower anterior components in the left eye than in the right eye. Preventing the chance of acute primary angle closure attack, the patient underwent laser iridotomy in the left eye; however, long-term follow-up is needed. Additionally, we developed a hypothesis for the mechanism of unilateral angle closure despite high myopia by investigating the ocular structural parameters in detail.

The Molecular Basis of Human Anophthalmia and Microphthalmia

Human eye development is coordinated through an extensive network of genetic signalling pathways. Disruption of key regulatory genes in the early stages of eye development can result in aborted eye formation, resulting in an absent eye (anophthalmia) or a small underdeveloped eye (microphthalmia) phenotype. Anophthalmia and microphthalmia (AM) are part of the same clinical spectrum and have high genetic heterogeneity, with >90 identified associated genes. By understanding the roles of these genes in development, including their temporal expression, the phenotypic variation associated with AM can be better understood, improving diagnosis and management. This review describes the genetic and structural basis of eye development, focusing on the function of key genes known to be associated with AM. In addition, we highlight some promising avenues of research involving multiomic approaches and disease modelling with induced pluripotent stem cell (iPSC) technology, which will aid in developing novel therapies.

CHARGE syndrome: a review

CHARGE syndrome is a complex genetic syndrome, owing to the wide range of tissues/systems affected by mutations in the CHD7 gene. In this review, we discuss the diagnosis, clinical features and management of CHARGE syndrome.

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.

CHD7 deficiency in "Looper", a new mouse model of CHARGE syndrome, results in ossicle malformation, otosclerosis and hearing impairment

CHARGE syndrome is a rare human disorder caused by mutations in the gene encoding chromodomain helicase DNA binding protein 7 (CHD7). Characteristics of CHARGE are varied and include developmental ear and hearing anomalies. Here we report a novel mouse model of CHD7 dysfunction, termed Looper. The Looper strain harbours a nonsense mutation (c.5690C>A, p.S1897X) within the Chd7 gene. Looper mice exhibit many of the clinical features of the human syndrome, consistent with previously reported CHARGE models, including growth retardation, facial asymmetry, vestibular defects, eye anomalies, hyperactivity, ossicle malformation, hearing loss and vestibular dysfunction. Looper mice display an otosclerosis-like fusion of the stapes footplate to the cochlear oval window and blepharoconjunctivitis but not coloboma. Looper mice are hyperactive and have vestibular dysfunction but do not display motor impairment.

Congenital abnormalities of the optic nerve: from gene mutation to clinical expression

Optic nerve malformations are common causes of congenital blindness and are recognized with increasing prevalence. The importance of identifying these malformations lies not only in determining the cause and level of visual impairment, but also in looking for associated treatable or life threatening systemic conditions. A number of genetic mutations have been identified in the development of optic disc anomalies, such as ones in PAX2 or PAX6. Recent advances in genetic testing like array comparative genomic hybridization allow the detection of microdeletions that were previously difficult or impossible to identify.

Two cases of CHARGE syndrome with multiple congenital anomalies

We report on two cases of bilateral chorioretinal colobomas with ocular anomalies in patients with CHARGE syndrome. In the first case, a female infant was born at 36 + 5 weeks gestation. At birth, the patient demonstrated a small left eye. Slit-lamp examination revealed colobomas of both irises. Fundus examination showed both chorioretinal colobomas. Brain magnetic resonance imaging (MRI) showed left microphthalmia. Systemic evaluation revealed multiple congenital anomalies: benign external hydrocephalus, esophageal atresia with imperforate anus, atrial septal defect (ASD), ventricular septal defect, patent ductus arteriosis (PDA), and right mild hydronephrosis. In the second case, a male infant was born at 39 + 5 weeks gestation and demonstrated a dysmorphic appearance with an irregular left pupil and ptosis. Fundus examination of both eyes showed large chorioretinal colobomas involving the optic disc and posterior pole. The patient had multi-organ anomalies: right facial palsy, a left short, wide ear with a small lobe, congenital heart defects, such as ASD and PDA, left renal atresia, seizure disorder, and micropenis. Both cases revealed multiple anomalies including nearly all major and minor criteria of CHARGE syndrome which could be life-threatening to neonates. Thus, all neonates with ocular colobomas should have fully and detailed systemic examinations checking all minor criteria and even occasional findings of CHARGE syndrome.