Detailed analysis of retinal function and morphology in a patient with autosomal recessive bestrophinopathy (ARB)

Clinical and genetic features in autosomal recessive bestrophinopathy in Chinese cohort

PURPOSE

To provide a genotype and phenotype characterization of the BEST1 mutation in Chinese patients with autosomal recessive bestrophinopathy (ARB) through multimodal imaging and next-generation sequencing (NGS).

METHODS

Seventeen patients from 17 unrelated families of Chinese origin with ARB were included in a retrospective cohort study. Phenotypic characteristics, including anterior segment features, were assessed by multimodal imaging. Multigene panel testing, involving 586 ophthalmic disease-associated genes, and Sanger sequencing were performed to identify disease-causing variants.

RESULTS

Among 17 ARB patients, the mean follow-up was 15.65 months and average onset age was 30.53 years (range: 9-68). Best corrected visual acuity ranged from light perception to 0.8. EOG recordings showed a typically decreased Arden ratio in 12 patients, and a normal or slightly decreased Arden ratio in two patients. Anterior features included shallow anterior chambers (16/17), ciliary pronation (16/17), iris bombe (13/17), iridoschisis (2/17), iris plateau (1/17), narrow angles (16/17) and reduced axial lengths (16/17). Sixteen patients had multiple bilateral small, round, yellow vitelliform deposits distributed throughout the posterior pole, surrounding the optic disc. Initial diagnoses included angle-closure glaucoma (four patients), Best disease (three patients), and central serous chorioretinopathy secondary to choroidal neovascularization (CNV) (one patient), with the remainder diagnosed with ARB. Fourteen patients underwent preventive laser peripheral iridotomy, four of whom also received combined trabeculectomy and iridotomy in both eyes for uncontrolled intraocular pressure. One patient received intravitreal conbercept for CNV. Overall, 15 distinct disease-causing variants of BEST1 were identified, with 14 (82.35%) patients having missense mutations. Common mutations included p. Arg255-256 and p. Ala195Val (both 23.68%), with the most frequent sites in exons 7 and 5.

CONCLUSIONS

This study provides a comprehensive characterization of anterior segment and genetic features in ARB, with a wide array of morphological abnormalities. Findings are relevant for refining clinical practices and genetic counseling and advancing pathogenesis research.

Detection of Novel BEST1 Variations in Autosomal Recessive Bestrophinopathy Using Third-generation Sequencing

OBJECTIVE

Autosomal recessive bestrophinopathy (ARB), a retinal degenerative disease, is characterized by central visual loss, yellowish multifocal diffuse subretinal deposits, and a dramatic decrease in the light peak on electrooculogram. The potential pathogenic mechanism involves mutations in the BEST1 gene, which encodes Ca2+-activated Cl- channels in the retinal pigment epithelium (RPE), resulting in degeneration of RPE and photoreceptor. In this study, the complete clinical characteristics of two Chinese ARB families were summarized.

METHODS

Pacific Biosciences (PacBio) single-molecule real-time (SMRT) sequencing was performed on the probands to screen for disease-causing gene mutations, and Sanger sequencing was applied to validate variants in the patients and their family members.

RESULTS

Two novel mutations, c.202T>C (chr11:61722628, p.Y68H) and c.867+97G>A, in the BEST1 gene were identified in the two Chinese ARB families. The novel missense mutation BEST1 c.202T>C (p.Y68H) resulted in the substitution of tyrosine with histidine in the N-terminal region of transmembrane domain 2 of bestrophin-1. Another novel variant, BEST1 c.867+97G>A (chr11:61725867), located in intron 7, might be considered a regulatory variant that changes allele-specific binding affinity based on motifs of important transcriptional regulators.

CONCLUSION

Our findings represent the first use of third-generation sequencing (TGS) to identify novel BEST1 mutations in patients with ARB, indicating that TGS can be a more accurate and efficient tool for identifying mutations in specific genes. The novel variants identified further broaden the mutation spectrum of BEST1 in the Chinese population.

Typical best vitelliform dystrophy secondary to biallelic variants in BEST1

BACKGROUND

Pathogenic variants in BEST1 can cause autosomal dominant or autosomal recessive dystrophy, typically associated with distinct retinal phenotypes. In heterozygous cases, the disorder is commonly characterized by yellow sub-macular lesions in the early stages, known as Best vitelliform macular dystrophy (BVMD). Biallelic variants usually cause a more severe phenotype including diffuse retinal pigment epithelial irregularity and widespread generalized progressive retinopathy, known as autosomal recessive bestrophinopathy (ARB). This study describes three cases with clinical changes consistent with BVMD, however, unusually associated with autosomal recessive inheritance.

MATERIALS AND METHODS

Detailed ophthalmic workup included comprehensive ophthalmologic examination, multimodal retinal imaging, full-field and pattern electroretinography (ERG; PERG), and electrooculogram (EOG). Genetic analysis of probands and segregation testing and fundus examination of proband relatives was performed where possible.

RESULTS

Three unrelated cases presented with a clinical phenotype typical for BVMD and were found to have biallelic disease-causing variants in BEST1. PERG P50 and ERG were normal in all cases. The EOG was subnormal (probands 1 and 3) or normal/borderline (proband 2). Probands 1 and 2 were homozygous for the BEST1 missense variant c.139C>T, p.Arg47Cys, while proband 3 was homozygous for a deletion, c.536_538delACA, p.Asn179del. The parents of proband 1 were phenotypically normal. Parents of proband 1 and 2 were heterozygous for the same missense variant.

CONCLUSIONS

Individuals with biallelic variants in BEST1 can present with a phenotype indistinguishable from BVMD. The same clinical phenotype may not be evident in those harboring the same variants in the heterozygous state. This has implications for genetic counselling and prognosticationA.

Paradoxical autosomal recessive bestrophinopathy-like phenotypes shown in an autosomal dominant pedigree

PURPOSE

This study aimed to evaluate the clinical and genetic characteristics of eight members from a Chinese Han family who displayed autosomal recessive bestrophinopathy (ARB)-like retinal changes in autosomal dominant (AD) inheritance pattern.

METHODS

Clinical investigations included slit-lamp, tonometry, fundus photography, spectral-domain optical coherence tomography, fundus autofluorescence, electrooculography, and ultrasound biomicroscopy. Ocular axial length measurements were collected retrospectively. The targeted exome sequencing (TES) was applied for the genetic analysis of the proband. PCR-based Sanger sequencing was performed on the family for validation and co-segregation analysis.

RESULTS

Eight members in the three-generation pedigree complained about vision loss and seven of them had detailed clinical assessments, demonstrating ocular phenotypes including extramacular and vascular arcades subretinal deposits and Arden ratio decline on electrooculography that resembled ARB. Bilateral anterior chamber structure abnormalities were observed in seven cases and three patients were diagnosed with angle-closure glaucoma. Despite clinical phenotypes supporting ARB, there was only a single heterozygous mutation of c.227T > C (p.Ile76Thr) in the BEST1 gene detected in all eight patients, which showcased AD inheritance.

CONCLUSIONS

An ARB-like phenotype could be caused by a heterozygous mutation of the BEST1 gene and inherited in an AD fashion.

Clinical Features and Genetic Findings of Autosomal Recessive Bestrophinopathy

Autosomal recessive bestrophinopathy (ARB) is a rare subtype of bestrophinopathy caused by biallelic mutations of the BEST1 gene. ARB is characterized by multifocal subretinal deposits accompanied by macular edema or subretinal fluid, hyperopia, co-existing narrow angle, and a marked decrease in electrooculogram. However, little is known about the genetic variants and specific clinical features of ARB. This is an observational case series of patients with a clinical and genetic diagnosis of ARB who underwent multimodal imaging. We describe ten patients from nine unrelated families with six known variants and three novel missense variants: c.236C→T, p.(Ser79Phe); C.452C→T, p.(Leu151Pro); and c.650C→T, p.(Trp217Met). The most common variant was c.584C→T, p.(Ala195Val), observed in six patients, without correlation to the severity of the phenotype. All patients manifested bilateral multifocal subretinal deposits and subretinal fluid throughout the follow-up period, while intraretinal fluid was found in approximately half of the eyes. The extent or chronicity of the fluid collection did not correlate with visual acuity. Angle-closure glaucoma was present in five eyes. Three patients had a genetically confirmed family history of ARB, and one patient had a clinically suspected family history. This study reveals novel mutations in the BEST1 gene and adds to the spectrum of clinical presentations of ARB.

Clinical and instrumental characteristics of various forms of vitelliform dystrophies occurring in adult patient

Background. Vitelliform dystrophies, first detected in adulthood, may create complications in diagnosis, especially with partial or almost complete destruction of vitelliform material, disguising as various types of macular pathology, such as central serous chorioretinopathy, age-related macular degeneration.

The aim: to study the clinical and instrumental characteristics of the most common forms of vitelliform dystrophies occurring in adulthood.

Materials and methods. Sixty eyes of adult patients with vitelliform dystrophies were included in the study. All patients underwent ophthalmologic examination including family history, best corrected visual acuity, biomicroscopy, and multimodal imaging including fundus photo, SD-OCT, OCT-A, BAF, FA, ICGA. After examination, the patients were divided according to various types of vitelliform dystrophies. The instrumental and diagnostic characteristics of the identified forms of vitelliform dystrophies were studied, taking into account the stage of the process, based on the analysis of clinical data, as well as the results of the most accessible non-invasive research methods, such as SD-OCT, OCT-A, BAF.

Results. The average age of patients was 52.40 ± 20.62 years, there were 13 (43.3 %) women and 17 (56.7 %) men. In 96.67 % of cases, the disease was bilateral. Genetically determined forms of vitelliform dystrophies were more common in sporadic forms. In the studied cohort, 43.3  % were patients with Best vitelliform macular dystrophy, 13.3 % – with autosomal recessive bestrophinopathy, 43.3 % – with pattern dystrophies. In all patients, according to structural OCT data, neuroepithelium detachment, residual vitelliform material in the form of massive deposits, deposits in the form of “stalactites”, “fringes” were determined. In all cases of vitelliform dystrophies, atrophic changes were detected, which intensified with an increase in the duration of the disease. Hyperautofluorescence of the residual vitelliform material in the form of “beads” was often accompanied in the later stages of the disease.

Conclusion. Cases of vitelliform dystrophies identified in adults with partially resorbed vitelliform material require a thorough analysis of structural optical coherence tomography and fundus autofluorescence. 

Clinical reassessments and whole-exome sequencing uncover novel BEST1 mutation associated with bestrophinopathy phenotype

BACKGROUND

The diagnosis of retinal dystrophies can be challenging due to the spectrum of protean phenotypic manifestations. This study employed trio-whole-exome sequencing (trio-WES) to unveil the genetic cause of an inherited retinal disorder in a south Indian family.

MATERIALS AND METHODS

Proband's initial ophthalmic examinations was performed in the year 2016. WES was performed on a proband-parent trio to identify causative mutation followed by Sanger validation, segregation analysis, sequence and structure-based computational analysis to assess its pathogenicity. Based on the genetic findings, detailed clinical reassessments were performed in year 2020 for the proband and available family members.

RESULTS

WES revealed a novel homozygous BEST1 mutation c.G310A (p.D104N) in the proband and heterozygous for the parents, indicating autosomal recessive inheritance. Segregation analysis showed heterozygous mutation in maternal grandfather and normal genotype for younger brother and maternal grandmother. Moreover, the structure-based analysis revealed the mutation p.D104N in the cytoplasmic domain, causing structural hindrance by altering hydrogen bonds and destabilizing the BEST1 protein structure. Proband's clinical assessments were consistent with autosomal recessive bestrophinopathy (ARB) phenotype. Additionally, characteristic absent light rise and decreased light peak-to-dark trough ratio (LP:DT) was observed bilaterally in EOG.

CONCLUSIONS

Our study demonstrates the utility of WES and clinical re-evaluations in establishing the precise diagnosis of autosomal recessive bestrophinopathy associated with a novel mutation, thus expanding the BEST1-related mutation spectrum.

Phenotypic and Genetic Spectrum of Autosomal Recessive Bestrophinopathy and Best Vitelliform Macular Dystrophy

Purpose

Autosomal recessive bestrophinopathy (ARB) and vitelliform macular dystrophy (VMD) are distinct phenotypes, typically inherited through recessive and dominant patterns, respectively. Recessively inherited VMD (arVMD) has been reported, suggesting that dominant and recessive BEST1-related retinopathies represent a single disease spectrum. This study compares adVMD, arVMD, and ARB to determine whether a continuum exists and to define clinical and genetic features to aid diagnosis and management.

Methods

One arVMD patient and nine ARB patients underwent standard ophthalmic examination, imaging, electrophysiology, and genetic assessments. A meta-analysis of reported BEST1 variants was compiled, and clinical parameters were analyzed with regard to inheritance and phenotype.

Results

Among 10 patients with biallelic BEST1 variants, three novel ARB variants (p.Asp118Ala, p.Leu224Gln, p.Val273del) were discovered. A patient with homozygous p.Glu35Lys was clinically unique, presenting with VMD, including hyperautofluorescence extending beyond the macula, peripheral punctate lesions, and shortened axial-length. A tritan-axis color vision deficit was seen in three of six (50%) of ARB patients. Attempts to distinguish recessively-inherited ARB and dominantly-inherited VMD genotypically, by variant frequency and residue location, did not yield significant differences. Literature meta-analysis with principle component analysis of clinical features demonstrated a spectrum of disease with arVMD falling between adVMD and ARB.

Conclusions

This study suggests that arVMD is part of a continuum of autosomal recessive and dominant BEST1-related retinopathies. Detailed clinical and molecular assessments of this cohort and the literature are corroborated by unsupervised analysis, highlighting the overlapping heterogeneity among BEST1-associated clinical diagnoses. Tritan-axis color vision deficit is a previously unreported finding associated with ARB.

Bestrophinopathies: perspectives on clinical disease, Bestrophin-1 function and developing therapies

Bestrophinopathies are a group of clinically distinct inherited retinal dystrophies that typically affect the macular region, an area synonymous with central high acuity vision. This spectrum of disorders is caused by mutations in bestrophin1 (BEST1), a protein thought to act as a Ca²⁺-activated Cl^- channel in the retinal pigment epithelium (RPE) of the eye. Although bestrophinopathies are rare, over 250 individual pathological mutations have been identified in the BEST1 gene, with many reported to have various clinical expressivity and incomplete penetrance. With no current clinical treatments available for patients with bestrophinopathies, understanding the role of BEST1 in cells and the pathological pathways underlying disease has become a priority. Induced pluripotent stem cell (iPSC) technology is helping to uncover disease mechanisms and develop treatments for RPE diseases, like bestrophinopathies. Here, we provide a comprehensive review of the pathophysiology of bestrophinopathies and highlight how patient-derived iPSC-RPE are being used to test new genomic therapies in vitro.

Induced Pluripotent Stem Cell Modeling of Best Disease and Autosomal Recessive Bestrophinopathy

PURPOSE

To understand the pathophysiology of Best disease (BD) and autosomal recessive bestrophinopathy (ARB) by establishing an in vitro model using human induced pluripotent stem cell (iPSC).

MATERIALS AND METHODS

Human iPSC lines were generated from mononuclear cells in peripheral blood of one ARB patient, one autosomal dominant BD patient, and two normal controls. Immunocytochemistry and reverse transcriptase polymerase chain reaction in iPSC lines were conducted to demonstrate the pluripotent markers. After the differentiation of iPSC into functional retinal pigment epithelium (RPE), morphological characteristics of the RPE were evaluated using confocal microscopy and immunocytochemistry. The rates of fluid flow across iPSC-RPE monolayer were measured to compare apical to basal fluid transports by RPE. RNA sequencing was performed on iPSC-RPE to identify the differences in gene expression profiles, and specific gene sets were tested using Gene Set Enrichment Analysis.

RESULTS

Morphological characteristics, gene expression, and epithelial integrity of ARB iPSC were comparable to those of BD patient or normal control. Fluid transport from apical to basal was significantly decreased in ARB iPSC-RPE compared with BD iPSC-RPE or control iPSC-RPE. Gene Set Enrichment Analysis confirmed that ARB iPSC-RPE exhibited significant enrichments of epithelial-mesenchymal transition gene set and TNF-α signaling via NF-κB gene set compared to control iPSC-RPE or BD iPSC-RPE.

CONCLUSION

A human iPSC model of ARB showed a functional deficiency rather than anatomical defects. ARB may be caused by RPE dysfunction following BEST1 mutation.

MAINTENANCE OF GOOD VISUAL ACUITY IN BEST DISEASE ASSOCIATED WITH CHRONIC BILATERAL SEROUS MACULAR DETACHMENT

PURPOSE

We describe the long-term follow-up of a patient with multifocal Best disease with chronic bilateral serous macular detachment and unusual peripheral findings associated with a novel mutation in the BEST1 gene.

METHODS

Case report.

RESULTS

A 59-year-old white woman was referred for an evaluation of her macular findings in 1992. There was a family history of Best disease in the patient's mother and a male sibling. Her medical history was unremarkable. Best-corrected visual acuity was 20/20 in her right eye and 20/25 in her left eye. The anterior segment examination was normal in both eyes. Funduscopic examination showed multifocal hyperautofluorescent vitelliform deposits with areas of subretinal fibrosis in both eyes. An electrooculogram showed Arden ratios of 1.32 in the right eye and 1.97 in the left eye. Ultra-widefield color and fundus autofluorescence imaging showed degenerative retinal changes in areas throughout the entire fundus in both eyes. Optical coherence tomography, including annual eye-tracked scans from 2005 to 2016, showed persistent bilateral serous macular detachments. Despite chronic foveal detachment, visual acuity was 20/25 in her right eye and 20/40 in her left eye, 24 years after initial presentation. Genetic testing showed a novel c.238T>A (p.Phe80Ile) missense mutation in the BEST1 gene.

CONCLUSION

Some patients with Best disease associated with chronic serous macular detachment can maintain good visual acuity over an extended follow-up. To our knowledge, this is the first report of Best disease associated with this mutation in the BEST1 gene.

Clinical and Genetic Findings of Autosomal Recessive Bestrophinopathy (ARB)

Mutations in BEST1 cause several phenotypes including autosomal dominant (AD) Best vitelliform macular dystrophy type 2 (BVMD), AD vitreo-retino-choroidopathy (ADVIRC), and retinitis pigmentosa-50 (RP50). A rare subtype of Bestrophinopathy exists with biallelic mutations in BEST1. Its frequency is estimated to be 1/1,000,000 individuals. Here we report 6 families and searched for a genotype-phenotype correlation. All patients were referred due to reduced best-corrected visual acuity (BCVA), ranging from 0.1/10 to 3/10. They all showed vitelliform lesions located at the macula, sometimes extending into the midperiphery, along the vessels and the optic disc. Onset of the disease varied from the age of 3 to 25 years. Electrooculogram (EOG) revealed reduction in the EOG light rise in all patients. Molecular analysis revealed previously reported mutations p.(E35K);(E35K), p.(L31M);(L31M), p.(R141H);(A195V), p.(R202W);(R202W), and p.(Q220*);(Q220*) in five families. One family showed a novel mutation: p.(E167G);(E167G). All mutations were heterozygous in the parents. In one family, heterozygous children showed various reductions in the EOG light rise and autofluorescent deposits. Autosomal recessive Bestrophinopathy (ARB), although rare, can be recognized by its phenotype and should be validated by molecular analysis. Genotype-phenotype correlations are difficult to establish and will require the analysis of additional cases.

Pathogenicity of new BEST1 variants identified in Italian patients with best vitelliform macular dystrophy assessed by computational structural biology

Background

Best vitelliform macular dystrophy (BVMD) is an autosomal dominant macular degeneration. The typical central yellowish yolk-like lesion usually appears in childhood and gradually worsens. Most cases are caused by variants in the BEST1 gene which encodes bestrophin-1, an integral membrane protein found primarily in the retinal pigment epithelium.

Methods

Here we describe the spectrum of BEST1 variants identified in a cohort of 57 Italian patients analyzed by Sanger sequencing. In 13 cases, the study also included segregation analysis in affected and unaffected relatives. We used molecular mechanics to calculate two quantitative parameters related to calcium-activated chloride channel (CaCC composed of 5 BEST1 subunits) stability and calcium-dependent activation and related them to the potential pathogenicity of individual missense variants detected in the probands.

Results

Thirty-six out of 57 probands (63% positivity) and 16 out of 18 relatives proved positive to genetic testing. Family study confirmed the variable penetrance and expressivity of the disease. Six of the 27 genetic variants discovered were novel: p.(Val9Gly), p.(Ser108Arg), p.(Asn179Asp), p.(Trp182Arg), p.(Glu292Gln) and p.(Asn296Lys). All BEST1 variants were assessed in silico for potential pathogenicity. Our computational structural biology approach based on 3D model structure of the CaCC showed that individual amino acid replacements may affect channel shape, stability, activation, gating, selectivity and throughput, and possibly also other features, depending on where the individual mutated amino acid residues are located in the tertiary structure of BEST1. Statistically significant correlations between mean logMAR best-corrected visual acuity (BCVA), age and modulus of computed BEST1 dimerization energies, which reflect variations in the in CaCC stability due to amino acid changes, permitted us to assess the pathogenicity of individual BEST1 variants.

Conclusions

Using this computational approach, we designed a method for estimating BCVA progression in patients with BEST1 variants.

Novel BEST1 mutations and special clinical characteristics of autosomal recessive bestrophinopathy in Chinese patients

PURPOSE

The aim of this study was to describe the genetic and clinical characteristics of Chinese patients with autosomal recessive bestrophinopathy (ARB).

METHODS

This study presents a retrospective observational case series. Twenty-one ARB patients and 25 clinically healthy family members were recruited. The coding regions and adjacent intronic regions of BEST1 were analysed via Sanger sequencing. Clinical examinations, including ultrasound biomicroscopy, A-scan, optical coherence tomography, fundus autofluorescence, fundus fluorescein angiography (FFA), indocyanine green angiography (ICGA) and visual electrophysiology, were reviewed.

RESULTS

Six novel mutations (c.380C>T, p.T127M; c.397A>G, p.N133D; c.500A>G, p.E167G; c.817G>A, p.V273M; c.174_176del, p.Q58del; and c.950_955del, p.S318_L319) and 8 previously reported mutations were identified. The p.R255W mutation had the highest frequency in our cohort. Twenty patients had serous retinal detachment with multifocal subretinal vitelliform deposits in the posterior poles. One patient exhibited chorioretinal atrophy. FFA revealed peripheral vascular leakage in 10 patients, and ICGA revealed hyperfluorescent spots in 8 patients. Visual electrophysiology was abnormal in all patients. Fifteen patients with angle closure (AC) or angle-closure glaucoma (ACG) had shallower anterior chambers and shorter axial lengths than the patients with open angle, contributing to their risk of developing AC/ACG. One patient developed AC during the 7-year follow-up period. The misdiagnosis and missed rates were 35.3% and 58.8%, respectively.

CONCLUSION

The six novel mutations and high frequency of p.R255W suggest ethnical differences in the BEST1 mutation spectrum among Chinese patients. BEST1 gene screening and detailed clinical examinations help establishing a diagnosis of ARB. Clinical evaluations of the risk of developing AC/ACG are recommended for ARB patients.

Idiopathic Acute Exudative Polymorphous Vitelliform Maculopathy: Clinical Spectrum and Multimodal Imaging Characteristics

PURPOSE

To describe clinical findings in patients with acute exudative polymorphous vitelliform maculopathy (AEPVM).

DESIGN

Retrospective, observational, multicenter case series review.

PARTICIPANTS

Consecutive patients diagnosed with idiopathic AEPVM.

METHODS

Review of clinical charts, multimodal imaging, electrophysiologic findings, and genetic findings in previously unpublished patients and review of the literature.

MAIN OUTCOME MEASURES

Clinical features of idiopathic AEPVM and differential diagnosis.

RESULTS

Eighteen patients (age range, 21-74 years) with typical features of AEPVM, including initial localized, serous detachments followed by the development of characteristic yellow-white deposits in the vitelliform space. Over time, this hyperautofluorescent material gravitated within the larger lesions, resulting in typical curvilinear deposits characteristic of later stages. Symptoms and clinical findings lasted from weeks to several years. Some patients showed previously undescribed features such as fluorescein-negative intraretinal cystic changes, choroidal neovascularization, serous retinal elevations mimicking retinal folds, increased choroidal thickness, lack of rapid visual recovery, and recurrence years after complete resolution of initial manifestations.

CONCLUSIONS

Acute exudative polymorphous vitelliform maculopathy can present with a more variable natural course than previously described. Paraneoplastic retinopathy and autosomal recessive bestrophinopathy closely resemble AEPVM, necessitating medical and hereditary evaluation to exclude these clinical possibilities. This series of patients with AEPVM expands the clinical spectrum of the disorder, including demographics, clinical manifestations, imaging features, natural course, and visual prognosis.

Ten-Year Follow-Up after Bilateral Submacular Neovascular Membrane Removal in a Case of Autosomal Recessive Bestrophinopathy

Herein, we report the case of an 8-year-old girl who presented in December 2000 with a submacular neovascular membrane in the right eye, with a clinical diagnosis of Best disease. At that time, she underwent pars plana vitrectomy (PPV) with removal of the subretinal choroidal neovascularization (CNV). Her vision improved from 20/200 to 20/25. Four years later, a new CNV developed in the other eye. Initially, she underwent unsuccessful photodynamic therapy. As her vision worsened, she underwent a second, this time successful, PPV with membrane removal in the left eye, with vision improving to 20/30. Ten years later, she returned complaining of vision loss over the last year. Her vision was 20/200 OU, and optical coherence tomography demonstrated very large intraretinal cystoid spaces resembling bilateral macular schisis. Four ranibizumab injections as well as dorzolamide eye drops were tried, both without success. Finally, she underwent PPV with internal limiting membrane peeling and gas-fluid exchange in the left eye. One month later, the macula appeared flat and vision had improved to 20/60. The same procedure was performed 1 year later for the right eye, with vision improving to 20/80. One year later, mild cystic spaces developed again in both eyes, although much smaller than previously observed. Her vision remained stable.

Clinical and Genetic Findings of Autosomal Recessive Bestrophinopathy in Japanese Cohort

PURPOSE

To report the clinical and genetic findings of 9 Japanese patients with autosomal recessive bestrophinopathy (ARB).

DESIGN

Retrospective, multicenter observational case series.

METHODS

Nine ARB patients from 7 unrelated Japanese families that were examined in 3 institutions in Japan were studied. A series of ophthalmic examinations including fundus photography, spectral-domain optical coherence tomography, fundus autofluorescence, electrooculography (EOG), electroretinography, and the results of genetic analysis were reviewed.

RESULTS

Genetic analyses identified 7 pathogenic variants in BEST1 including 2 novel variants, c.478G>C (p.A160P) and c.948+1delG. Homozygous variants were found in 4 families and compound heterozygous variants were found in 3 families. Two patients were diagnosed as ARB only after the whole exome sequencing analyses. The Arden ratio of the EOG was less than 1.5 in all 7 patients tested. Vitelliform lesions typical for Best vitelliform macular dystrophy were not seen in any of the patients. Seven patients shared some of the previously described features of ARB: subretinal deposits, extensive subretinal fluid, and cystoid macular edema (CME). However, the other 2 patients with severe retinal degeneration lacked these features. Focal choroidal excavations were present bilaterally in 2 patients. One case had a marked reduction of the CME and expansion of subretinal deposits over an 8-year of follow-up period.

CONCLUSIONS

Japanese ARB patients had some but not all of the previously described features. Genetic analyses are essential to diagnose ARB correctly in consequence of considerable phenotypic variations.

Detailed analysis of family with autosomal recessive bestrophinopathy associated with new BEST1 mutation

Purpose

To describe the clinical and genetic findings in a patient with autosomal recessive bestrophinopathy (ARB) and his healthy parents.

Methods

The patient and his healthy non-consanguineous parents underwent detailed ophthalmic evaluations including electro-oculography (EOG), spectral-domain optical coherence tomography (SD-OCT), and fundus autofluorescence (FAF) imaging. Mutation analysis of the BEST1 gene was performed by Sanger sequencing.

Results

The FAF images showed multiple spots of increased autofluorescence, and the sites of these spots corresponded to the yellowish deposits detected by ophthalmoscopy. SD-OCT showed cystoid macular changes and a shallow serous macular detachment. The Arden ratio of the EOG was markedly reduced to 1.1 in both eyes. Genetic analysis of the proband detected two sequence variants of the BEST1 gene in the heterozygous state: a novel variant c.717delG, p.V239VfsX2 and an already described c.763C>T, p.R255W variant associated with Best vitelliform macular dystrophy and ARB. The proband’s father carried the c.717delG, p.V239VfsX2 variant in the heterozygous state, and the mother carried the c.763C>T, p.R255W variant in the heterozygous state. The parents who were heterozygous for the BEST1 variants had normal visual acuity, EOG, SD-OCT, and FAF images.

Conclusions

In a truncating BEST1 mutation, the phenotype associated with ARB is most likely due to a marked decrease in the expression of BEST1 promoted by the nonsense-mediated decay surveillance mechanism, and it may depend on the position of the premature termination of the codon created.

New best1 mutations in autosomal recessive bestrophinopathy

PURPOSE

To report the ocular phenotype in patients with autosomal recessive bestrophinopathy and carriers, and to describe novel BEST1 mutations.

METHODS

Patients with clinically suspected and subsequently genetically proven autosomal recessive bestrophinopathy underwent full ophthalmic examination and investigation with fundus autofluorescence imaging, spectral domain optical coherence tomography, electroretinography, and electrooculography. Mutation analysis of the BEST1 gene was performed through direct Sanger sequencing.

RESULTS

Five affected patients from four families were identified. Mean age was 16 years (range, 6-42 years). All affected patients presented with reduced visual acuity and bilateral, hyperautofluorescent subretinal yellowish deposits within the posterior pole. Spectral domain optical coherence tomography demonstrated submacular fluid and subretinal vitelliform material in all patients. A cystoid maculopathy was seen in all but one patient. In 1 patient, the location of the vitelliform material was seen to change over a follow-up period of 3 years despite relatively stable vision. Visual acuity and fundus changes were unresponsive to topical and systemic carbonic anhydrase inhibitors and systemic steroids. Carriers had normal ocular examinations including normal fundus autofluorescence. Three novel mutations were detected.

CONCLUSION

Three novel BEST1 mutations are described, suggesting that many deleterious variants in BEST1 resulting in haploinsufficiency are still unknown. Mutations causing autosomal recessive bestrophinopathy are mostly located outside of the exons that usually harbor vitelliform macular dystrophy-associated dominant mutations.

Biallelic Mutations in the BEST1 Gene: Additional Families with Autosomal Recessive Bestrophinopathy

PURPOSE

To describe the genotype and phenotype of patients with autosomal recessive bestrophinopathy (ARB), and heterozygous carriers.

METHODS

The members of three unrelated ARB families were investigated. Molecular genetic analysis was performed on 11 members of these families. Ten members were examined clinically; including visual acuity, slit-lamp examination, biomicroscopy, fundus photography, and Goldmann applanation tonometry. Measurements were also made of the anterior chamber depth and axial length, and optical coherence tomography (OCT), electrooculography (EOG), and full-field electroretinography (full-field ERG) were performed. Multifocal electroretinography (mfERG) was performed on eight members of these families.

RESULTS

Two novel combinations of missense mutations in the BEST1 gene were identified: p.R141H/p.M325T in three patients with ARB in two unrelated Norwegian families, and p.R141H/p.I201T was found in an ARB patient in a Swedish family. All four patients with ARB had clinical and electrophysiological features of ARB. All the heterozygous carriers of the p.R141H mutation were clinically normal, and showed normal OCT, EOG and full-field ERG findings, but had mildly abnormal mfERG results. Only one heterozygous carrier of the p.M325T mutation was studied and he was clinically normal, showing normal OCT and full-field ERG results, but subnormal EOG and mfERG findings. The heterozygous carrier of the p.I201T mutation was clinically normal, showing normal OCT, EOG and full-field ERG results, but subnormal mfERG results.

CONCLUSIONS

We have shown that the two novel combinations of compound heterozygous mutations p.R141H/p.M325T and p.R141H/p.I201T in the BEST1 gene can also lead to the ARB phenotype.

Screening for BEST1 gene mutations in Chinese patients with bestrophinopathy

PURPOSE

The purpose of this study was to analyze BEST1 gene mutations in Chinese patients with bestrophinopathy and to describe the clinical features of these patients.

METHODS

Thirteen patients from 12 unrelated Chinese families affected by bestrophinopathy were recruited and clinically evaluated with best-corrected visual acuity examination, slit-lamp biomicroscopy, fundus examination and photography, optical coherence tomography, fundus autofluorescence, electro-oculography, and electroretinography. Blood samples were collected for DNA extraction. Mutation analysis was performed by direct sequencing of the BEST1 gene. One hundred control chromosomes were also screened to exclude nonpathogenic polymorphisms.

RESULTS

Seven patients showed clinical pictures of Best vitelliform macular dystrophy (BVMD) and harbored heterozygous mutations compatible with autosomal dominant inheritance. Two novel mutations (p.T4I and p.A291V) and three reported mutations (p.R218C, p.Q293H, and p.D301G) were identified. Six patients carried BEST1 mutations on both alleles compatible with autosomal recessive inheritance. Compound heterozygous mutations were detected in four patients who presented a BVMD phenotype, while homozygous mutations were detected in two patients with autosomal recessive bestrophinopathy. Mutation analysis revealed eight mutations. Four (p.Y33H, p.R130L, p.M163R, and c.519delA) were novel, and four (p.R13H, p.A195V, p.R255W, and p.W287*) had previously been reported.

CONCLUSIONS

Patients with biallelic BEST1 mutations were common among Chinese patients with bestrophinopathy, and the phenotypes varied. The features and combinations of different BEST1 mutations as well as epistatic effects may influence phenotype expression. Our results expand the BEST1 mutation spectrum.

Best disease associated with macular hole

PURPOSE

To report a case of Best vitelliform macular dystrophy complicated by macular hole.

METHODS

History and clinical examination, electroretinogram, and optical coherence tomography.

RESULTS

We report a case of a 20-year-old boy with progressive visual loss in his left eye. In fundus examination, there was a typical vitelliform lesion in the right eye and a macular hole in the left eye. The electroretinogram Arden ratio was <1.1 in both eyes. Optical coherence tomography revealed deposition of hyperreflective material and hyporeflective area between the junction of the inner segment and outer segment of the photoreceptors and the retinal pigment epithelium in the right eye, and large full-thickness macular hole with cystoid changes in the retinal layers in the left eye. There was no associated retinal detachment.

CONCLUSION

Although extremely rare, macular hole should be considered as a cause of the significant visual loss in patients with Best vitelliform macular dystrophy.

Autosomal recessive bestrophinopathy associated with angle-closure glaucoma

PURPOSE

Abnormalities in the BEST1 gene have recently been recognised as causing autosomal recessive bestrophinopathy (ARB). ARB has been noted to have a variable phenotypic presentation, distinct from that of autosomal dominant Best vitelliform macular dystrophy (BVMD). Both conditions are associated with deposits in the retina, a reduced or absent electro-oculography (EOG) light rise, and the risk of developing angle-closure glaucoma. Herein, we describe the clinical and genetic characteristics of a young male diagnosed with ARB associated with angle-closure glaucoma resulting from a novel homozygous mutation in BEST1.

METHODS

All research involved in this case adhered to the tenets of the Declaration of Helsinki. The proband underwent slitlamp examination, retinal autofluorescence imaging and optical coherence tomography after presenting with deteriorating vision. The findings prompted genetic testing with bi-directional DNA sequencing of coding and flanking intronic regions of BEST1. The proband's family members were subsequently screened.

RESULTS

A provisional diagnosis of ARB was made based on the findings of subretinal and schitic lesions on fundoscopy and retinal imaging, together with abnormal EOG and electroretinography. Genetic testing identified a novel homozygous mutation in BEST1, c.636+1 G>A. Family members were found to carry one copy of the mutation and had no clinical or electrophysiological evidence of disease. The proband was additionally diagnosed with angle-closure glaucoma requiring topical therapy, peripheral iridotomies and phacoemulsification.

CONCLUSIONS

Phenotypic overlap, reduced penetrance, variable expressivity and the ongoing discovery of new forms of bestrophinopathies add to the difficulty in distinguishing these retinal diseases. All patients diagnosed with ARB or BVMD should be examined for narrow angles and glaucoma, given their frequent association with these conditions.

Ocular phenotype analysis of a family with biallelic mutations in the BEST1 gene

PURPOSE

To investigate the genetic cause and perform a comprehensive clinical analysis of a Danish family with autosomal recessive bestrophinopathy; to investigate whether Bestrophin may be expressed in normal human retina.

DESIGN

Retrospective clinical and molecular genetic analysis and immunohistochemical observational study.

METHODS

setting: National referral center. participants: A family with 5 individuals and biallelic BEST1 mutations, and enucleated eyes from 2 individuals with nonaffected retinas. observation procedures: Molecular genetic analysis included sequencing of BEST1 and co-segregation analysis. Clinical investigations included electro-oculography, full-field electroretinography, multifocal electroretinography, spectral-domain optical coherence tomography, and fundus autofluorescence imaging. Immunohistochemical analysis was performed. main outcome measures: BEST1 mutations, imaging findings, electroretinography amplitudes, and implicit times.

RESULTS

The index case was compound heterozygous for p.A195V and a novel 15 base pair deletion leading to p.Q238L. The index case at age 10 demonstrated multifocal vitelliform changes that were hyperautofluorescent, cystoid macular edema in the inner nuclear layer, no light rise in the electro-oculography, and a reduced central but preserved peripheral retinal function by multifocal electroretinography. Full-field electroretinography demonstrated a reduced rod response and inner retina dysfunction. Retinal structure was normal in all 3 family members who carried a sequence change in BEST1. Electro-oculography light peak was reduced in both the mother and sister (heterozygous for p.Q238L). Immunohistochemistry could not confirm the presence of Bestrophin in normal human retina.

CONCLUSIONS

Because of a relatively well preserved retinal function, autosomal recessive bestrophinopathy may be a suitable first candidate, among the BEST1-related ocular conditions, for gene replacement therapy.

Value of anti-VEGF treatment in choroidal neovascularization associated with autosomal recessive bestrophinopathy

A 26-year-old white woman presented with a 1-year history of reduced vision in both eyes, bilateral yellowish deposits in the central macula, and pale yellow retinal flecks extending to midretinal periphery. Choroidal neovascularization (CNV) was confirmed in her left eye. On optical coherence tomography, both eyes showed diffuse intraretinal cystic spaces, thickening and separation of the photoreceptor layer from the retinal pigment epithelium (RPE), subretinal fluid, and focal thickening at the level of the RPE at the fovea. A diagnosis of autosomal recessive bestrophinopathy was confirmed by electrodiagnostic and molecular genetics testing. The CNV responded well to intravitreal ranibizumab therapy, and visual acuity in the left eye improved and stabilized; however, retinoschisis due to fluctuations in intraretinal fluid persisted. This case highlights the fact that current optical coherence tomography-driven protocols used widely to treat neovascular age-related macular degeneration may not be appropriate for CNV associated with other retinal diseases.

Autosomal recessive bestrophinopathy: differential diagnosis and treatment options

OBJECTIVE

To describe the clinical and genetic characteristics of patients with autosomal recessive bestrophinopathy (ARB).

DESIGN

Retrospective case series.

PARTICIPANTS

Ten patients with ARB from 7 different families.

METHODS

All patients underwent a complete ophthalmic examination, including dilated fundus examination, fundus photography, and fluorescein angiography (FA). In all probands, fundus autofluorescence (FAF) imaging, spectral-domain optical coherence tomography (OCT), full-field electroretinography (ERG), electro-oculography (EOG), and Goldmann perimetry were performed. In selected patients, multifocal ERG was performed. Blood samples were obtained to analyze the BEST1 gene for biallelic mutations that confirmed the diagnosis of ARB.

MAIN OUTCOME MEASURES

Age at onset; visual acuity; fundus appearance; characteristics on FA, FAF, OCT, full-field ERG, and EOG; BEST1 gene mutations; and genotype-phenotype correlation.

RESULTS

The age at onset varied widely, from 2 to 54 years. A spectrum of fundus abnormalities was observed, such as multifocal yellowish subretinal deposits, subretinal fibrous scars, and cystoid intraretinal fluid collections in the macula. All ARB patients were hyperopic, and some had shallow anterior chamber angles that predisposed them to angle-closure glaucoma. The EOG results were abnormal in all patients. The full-field ERG results were abnormal in 8 ARB patients, whereas 2 patients demonstrated normal cone and rod responses on full-field ERG. Nine ARB patients carried biallelic mutations in the BEST1 gene, and in 1 patient with a characteristic ARB phenotype, only 1 mutation could be identified. Seven different mutations were detected, including 4 novel mutations.

CONCLUSIONS

Autosomal recessive bestrophinopathy is a recognizable phenotype caused by autosomal recessively inherited mutations in the BEST1 gene. A differential diagnosis with other conditions can be made on the basis of marked autofluorescence changes in combination with an absent light rise on the EOG that outweighs the full-field ERG abnormalities, which point to the BEST1-related hereditary nature of the disease. A number of currently available therapeutic options should be considered in ARB, a disease that seems to be a suitable candidate for future gene therapy.

BEST1 sequence variants in Italian patients with vitelliform macular dystrophy

PURPOSE

To analyze the spectrum of sequence variants in the BEST1 gene in a group of Italian patients affected by Best vitelliform macular dystrophy (VMD).

METHODS

Thirty Italian patients with a diagnosis of VMD and 20 clinically healthy relatives were recruited. They belonged to 19 Italian families predominantly originating from central Italy. They received a standard ophthalmologic examination, OCT scan, and electrophysiological tests (ERG and EOG). Fluorescein and ICG angiographies and fundus autofluorescence imaging were performed in selected cases. DNA samples were analyzed for sequence variants of the BEST1 gene by direct sequencing techniques.

RESULTS

Nine missense variants and one deletion were found in the affected patients; each patient carried one mutation. Five variants [c.73C>T (p.Arg25Trp), c.652C>T (p.Arg218Cys), c.652C>G (p.Arg218Gly), c.728C>T (p.Ala243Val), c.893T>C (p.Phe298Ser)] have already been described in literature while another five variants [c.217A>C (p.Ile73Leu), c.239T>G (p.Phe80Cys), c.883_885del (p.Ile295del), c.907G>A (p.Asp303Asn), c.911A>G (p.Asp304Gly)] had not previously been reported. Affected patients, sometimes even from the same family, occasionally showed variable phenotypes. One heterozygous variant was also found in five clinically healthy relatives with normal fundus, visual acuity and ERG but with abnormal EOG.

CONCLUSIONS

Ten variants in the BEST1 gene were detected in a group of individuals with clinically apparent VMD, and in some clinically normal individuals with an abnormal EOG. The high prevalence of novel variants and the frequent report of a specific variant (p.Arg25Trp) that has rarely been described in other ethnic groups suggests a distribution of BEST1 variants peculiar to Italian VMD patients.

Unilateral vitelliform phenotype in autosomal recessive bestrophinopathy

AIMS

It was the aim of this study to report on a patient in whom a novel mutation in the BEST1 gene was responsible for unilateral vitelliform phenotype in autosomal recessive bestrophinopathy (ARB).

METHODS

An 8-year-old young girl (proband) with unilateral vitelliform phenotype underwent a complete ophthalmologic examination at baseline (time of diagnosis) and 2 years later. Genomic DNA was extracted to look for BEST1 gene mutations in the patient and her parents.

RESULTS

Fundus autofluorescence imaging and spectral-domain optical coherence tomography showed unchanged findings in the right eye over the 2-year follow-up period. Conversely, both fundus autofluorescence imaging and spectral-domain optical coherence tomography showed a partial reabsorption of the hyper-autofluorescent/hyper-reflective subretinal material in the left macula over the 2-year follow-up period. On BEST1 gene analysis, the patient presented a novel mutation c.535_537delAAC (p.Asn179del) in homozygous condition; interestingly, despite the absence of parents' consanguinity, both the father and mother showed the same novel mutation in heterozygous condition.

CONCLUSION

This case of unilateral vitelliform phenotype further supports the notion that ARB represents a disease spectrum in terms of severity, age at onset and heritability.

A novel compound heterozygous mutation in the BEST1 gene causes autosomal recessive Best vitelliform macular dystrophy

PURPOSE

To determine the genetic basis of early onset autosomal recessive Best vitelliform macular dystrophy (arBVMD) in a family with three affected children.

DESIGN

Clinical and family-based genetic study.

METHODS

Seven subjects making up a family with three children affected by Best vitelliform macular dystrophy were studied. Standard ophthalmic exam with dilated ophthalmoscopy and imaging were performed in each individual. The eleven exons of BEST1 were directly sequenced.

RESULTS

All three affected children have the clinical characteristic features of Best vitelliform macular dystrophy: large macular vitelliform lesions, scattered vitelliform lesions along the arcades and in the peripheral retina, and an accumulation of serous retinal fluid. A novel compound heterozygous mutation in the BEST1 gene was found in the three affected individuals (L41P and I201T). The unaffected parents and children only harbor one heterozygous mutation.

CONCLUSION

arBVMD can be caused by the compound heterozygous mutation L41P and I201T in the BEST1 gene.

Ocular phenotypes associated with biallelic mutations in BEST1 in Italian patients

PURPOSE

To report on the phenotype and the genotype of Italian patients carrying BEST1 mutations on both alleles.

METHODS

Five Italian patients from four independent pedigrees with retinal dystrophy associated with biallelic BEST1 variants were recruited from different parts of Italy. Molecular genetic analysis of the BEST1 gene was performed with direct sequencing techniques. All the subjects included in the study were clinically evaluated with a standard ophthalmologic examination, fundus photography, optical coherence tomography scan, and electrophysiological investigations.

RESULTS

Six BEST1 variants were identified. Three, c.1699del (p.Glu557AsnfsX52), c.625delAAC (p.Asn179del), and c.139C>T (p.Arg47Cys), were novel, and three had already been reported in the literature, c.301C>A(p.Pro101Thr), c.934G>A (p.Asp312Asn), and c.638A>G (p.Glu213Gly). Four were missense mutations, and two were deletions. Only one BEST1 mutation was located within one of the four mutational clusters described in typical autosomal dominant Best vitelliform macular dystrophy (BVMD). Four patients showed a BVMD phenotype while one patient presented a clinical picture consistent with autosomal recessive bestrophinopathy (ARB).

CONCLUSIONS

Biallelic BEST1 sequence variants can be associated with at least two different phenotypes: BVMD and ARB. The phenotypic result of the molecular changes probably depends on the characteristics and the combination of the different BEST1 mutations, but unknown modifying factors such as other genes or the environment may also play a role.

Clinical evaluation of two consanguineous families with homozygous mutations in BEST1

PURPOSE

To describe the clinical and genetic findings in two consanguineous families with Best vitelliform macular dystrophy (BVMD) and homozygous mutations in the bestrophin-1 (BEST1) gene.

METHODS

Ophthalmologic examination was performed in eight members of two families originating from Spain and Denmark. Mutation screening was performed using the Vitelliform Macular Dystrophy mutation array from Asper Biotech, and by the directed genomic sequencing of BEST1.

RESULTS

Two homozygous mutations were detected in these families. Mutation c.936C>A (p.Asp312Glu) has been reported previously in a Danish family; here, we describe four additional individuals in this family demonstrating findings compatible with a severe dominant BVMD, albeit with reduced penetrance in heterozygotes. In the Spanish family, a novel homozygous missense mutation in exon 4, c.388 C>A (p.Arg130Ser), was identified in the siblings. Homozygous siblings demonstrated evidence of multifocal vitelliform retinopathy, whereas heterozygous family members presented findings ranging from isolated reduction of the electrooculogram Arden ratio to normal values on all clinical parameters.

CONCLUSIONS

As demonstrated in these consanguineous families, a great clinical variability is associated with homozygous mutations in BEST1, ranging from severe dominant BVMD with reduced penetrance in heterozygotes to autosomal recessive bestrophinopathy.

Autosomal recessive vitelliform macular dystrophy in a large cohort of vitelliform macular dystrophy patients

PURPOSE

To report 11 cases of autosomal recessive vitelliform macular dystrophy and to compare their molecular findings and phenotypic characteristics with those of patients with the more common and well-described dominant form of the disease.

METHODS

Blood samples were obtained from 435 unrelated individuals with a clinical diagnosis of vitelliform macular dystrophy and screened for mutations in the coding sequences of BEST1. Medical records and retinal photographs of selected patients were reviewed.

RESULTS

Nine of the 435 probands were found to have 2 plausible disease-causing variations in BEST1, while 198 individuals were found to have heterozygous variations compatible with autosomal dominant inheritance. Inheritance phase was determined in three of the recessive families. Six novel disease-causing mutations were identified among these recessive patients: Arg47Cys, IVS7-2A>G, IVS7+4G>A, Ile205del12ATCCTGCTCCAGAG, Pro274Arg, and Ile366delCAGGTGTGGC. Forty-four novel disease-causing mutations were identified among the patients with presumed autosomal dominant disease. The phenotype of patients with recessive alleles for BEST1 ranged from typical vitelliform lesions to extensive extramacular deposits.

CONCLUSION

The authors provide evidence that two abnormal BEST1 alleles, neither of which causes macular disease alone, can act in concert to cause early-onset vitelliform macular dystrophy.

Autosomal recessive bestrophinopathy: new observations on the retinal phenotype - clinical and molecular report of an Italian family

PURPOSE

To describe the genotype and phenotype in a 9-year-old boy with bilateral retinopathy.

METHODS

The patient, his healthy (by history) nonconsanguineous parents and his sister were examined by best-corrected visual acuity, matrix frequency doubling technology, monocular static field analysis, fundus autofluorescence imaging, optical coherence tomography, Ganzfeld electroretinography (ERG), pattern ERG, multifocal ERG, electro-oculography and genotyping of the BEST1 gene.

RESULTS

The patient presented with an Arden ratio of 1.25, an unremarkable ERG and fluorescent yellow deposits distributed throughout the fundus suggestive of autosomal recessive bestrophinopathy (ARB). Genotyping revealed a homozygous nonsense mutation in BEST1 (p.R200X). The parents and the sister, who were heterozygous mutation carriers, presented with normal ophthalmological function.

CONCLUSIONS

ARB is a rare retinal disorder. We contribute a novel patient report indicative of ARB, assessed by clinical examination and confirmed by genotyping of BEST1, to the short list of ARB cases in the literature.

Phenotypic variability in a French family with a novel mutation in the BEST1 gene causing multifocal best vitelliform macular dystrophy

AIMS

To describe genetic and clinical findings in a French family affected by best vitelliform macular dystrophy (BVMD).

METHODS

We screened eight at-risk members of a family, including a BVMD-affected proband, by direct sequencing of 11 bestrophin-1 (BEST1) exons. Individuals underwent ophthalmic examination and autofluorescent fundus imaging, indocyanine green angiography, electro-oculogram (EOG), electroretinogram (ERG), multifocal ERG, optical coherence tomography (OCT), and where possible, spectral domain OCT.

RESULTS

The sequence analysis of the BEST1 gene revealed one previously unknown mutation, c.15C>A (p.Y5X), in two family members and one recently described mutation, c.430A>G (p.S144G), in five family members. Fundus examination and electrophysiological responses provided no evidence of the disease in the patient carrying only the p.Y5X mutation. Three patients with the p.S144G mutation did not show any preclinical sign of BVMD except altered EOGs. Two individuals of the family exhibited a particularly severe phenotype of multifocal BVMD-one individual carrying the p.S144G mutation heterozygously and one individual harboring both BEST1 mutations (p.S144G inherited from his mother and p.Y5X from his father). Both of these family members had multifocal vitelliform autofluorescent lesions combined with abnormal EOG, and the spectral domain OCT displayed a serous retinal detachment. In addition, ERGs demonstrated widespread retinal degeneration and multifocal ERGs showed a reduction in the central retina function, which could be correlated with the decreased visual acuity and visual field scotomas.

CONCLUSIONS

A thorough clinical evaluation found no pathological phenotype in the patient carrying the isolated p.Y5X mutation. The patients carrying the p.S144G variation in the protein exhibited considerable intrafamilial phenotypic variability. Two young affected patients in this family exhibited an early onset, severe, multifocal BVMD with a diffuse distribution of autofluorescent deposits throughout the retina and rapid evolution toward the loss of central vision. The other genetically affected relatives had only abnormal EOGs and displayed no or extremely slow electrophysiological evolution.

A synonymous codon variant in two patients with autosomal recessive bestrophinopathy alters in vitro splicing of BEST1

PURPOSE

Autosomal recessive bestrophinopathy (ARB) is a newly defined retinal dystrophy caused by biallelic mutations in bestrophin-1 (BEST1) and is hypothesized to represent the null bestrophin-1 phenotype in humans. The aim was to determine whether a synonymous BEST1 variant, c.102C>T, identified in two unrelated ARB patients, alters pre-mRNA splicing of the gene. Additionally a detailed phenotypic characterization of this distinctive condition is presented for both patients.

METHODS

BEST1 was analyzed by direct sequencing. Patients underwent standard ophthalmic assessment. In silico and in vitro analysis using a minigene system was performed to assess whether a synonymous variant identified, c.102C>T p.Gly34Gly, alters pre-mRNA splicing of BEST1.

RESULTS

Both ARB patients harbored either proven (patient 1; c.102C>T p.Gly34Gly and c.572T>C p.Leu191Pro) or presumed (patient 2; c.102C>T p.Gly34Gly and c.1470_1471delCA, p.His490GlnfsX24) biallelic mutations in BEST1 and were found to have phenotypes consistent with ARB. In vitro analysis of the synonymous variant, c.102C>T p.Gly34Gly, demonstrated it to introduce a cryptic splice donor site 52 nucleotides upstream of the actual splice donor site.

CONCLUSIONS

The novel BEST1 variant identified, c.102C>T p.Gly34Gly, alters pre-mRNA splicing in vitro and is potentially pathogenic. In vivo this splicing variant is predicted to lead to the production of an mRNA transcript with a premature termination codon (p.Glu35TrpfsX11) that is predicted to be degraded by NMD.

Morphological and functional changes in multifocal vitelliform retinopathy and biallelic mutations in BEST1

PURPOSE

To describe morphological and functional changes in a single patient with multifocal Best vitelliform macular dystrophy (BVMD) and to perform a genotype/phenotype correlation.

METHODS

The proband with multifocal BVMD and three of her family members were examined with electrooculography (EOG), full-field electroretinography (full-field ERG), multifocal electroretinography (mfERG) and optical coherence tomography (OCT). Genomic DNA was screened for mutation in the BEST1 gene by DNA sequencing analysis.

RESULTS

The proband was observed regularly during a follow-up period of 4 years. Full-field ERG demonstrated reduced and delayed responses of both rods and cones. OCT demonstrated intra- and subretinal fluid which seemed to fluctuate with periods of stress, similar to that seen in chronic central serous chorioretinopathy. Two distinct heterozygous BEST1 mutations were identified in the proband, the recurrent p.R141H mutation and the p.P233A mutation. Heterozygous p.R141H mutations were also identified in two family members, while p.P233A was a de novo mutation. Abnormal EOG findings were observed in both the proband and in the carriers of p.R141H. Heterozygous carriers showed delayed implicit times in a- and b-waves of combined total rod and cone full-field ERG responses.

CONCLUSIONS

The p.R141H mutation is frequently seen together with multifocal vitelliform retinopathy and biallelic mutations in BEST1. Our results show that carriers of the p.R141H mutation are clinically unaffected but present with abnormal EOG and full-field ERG findings. A patient with biallelic mutations of the BEST1 gene, causing multifocal BVMD with progressive, widespread functional disturbance of the retina, confirmed by full-field and mfERG is described.

BEST1-related autosomal dominant vitreoretinochoroidopathy: a degenerative disease with a range of developmental ocular anomalies

PURPOSE

To describe the spectrum of phenotypic characteristics of BEST1-related autosomal dominant vitreoretinochoroidopathy (ADVIRC) in a family with p.V86M mutation.

METHODS

A retrospective review of the clinical, psychophysical, and electrophysiological phenotypes of six subjects with ADVIRC. Five family members were sequenced for mutations in the BEST1 gene.

RESULTS

A heterozygous change, p.V86M (c.256G > A), was identified in the BEST1 gene in the three affected subjects tested, and was shown to segregate with the disease phenotype. The distance visual acuity ranged from ≥ 20/25 to absent perception of light. Clinical features observed included angle closure glaucoma (n = 2), microcornea with shallow anterior chamber (n = 1), iris dysgenesis (n = 2), cataracts (n = 4), classical peripheral concentric band of retinal hyperpigmentation (n = 5), and optic nerve dysplasia (n = 1). Full-field electroretinogram response amplitudes ranged from low normal (two cases; 27 and 32 years) to non-recordable (two cases; 42 and 63 years). Goldmann fields were normal in two (27 and 28 years) but were abnormal in two older subjects. Optical coherence tomography showed macular thinning in the proband, whereas his affected daughter had normal macular thickness. Electro-oculography showed borderline Arden's ratio (1.50) in the lone case tested (27 years).

CONCLUSION

ADVIRC is a slowly progressive vitreoretinal degeneration that demonstrates marked intra-familial phenotypic variability. Optic nerve dysplasia and iris dysgenesis are novel observations that extend the ocular phenotype of ADVIRC.

Childhood macular dystrophies

PURPOSE OF REVIEW

The aim of this review is to highlight recent advances in our understanding of the molecular genetic basis and phenotype of childhood onset macular dystrophies and to summarize current attempts to develop novel therapies for this group of disorders.

RECENT FINDINGS

The genes associated with the major causes of childhood onset macular dystrophies have now been identified and current research efforts have been focused on understanding the function of the encoded protein, how the mutant protein leads to photoreceptor cell death and investigation of the range of retinal phenotypes that result from mutations in these genes. Assessment of the phenotype has been greatly helped by improvements in retinal imaging such as spectral domain optical coherence tomography and fundus autofluorescence imaging. The development of animal models has, despite their limitations, helped understanding of disease mechanisms and allowed assessment of new therapeutic approaches such as gene replacement therapy and pharmacological treatments.

SUMMARY

Molecular diagnosis and improvements in retinal imaging have greatly improved the accuracy of diagnosis in paediatric macular disease and allowed better genetic counselling and information about prognosis to be given to children and their families. Advances in basic understanding of disease mechanism will lead to the development of clinical trials of novel therapies in the near future.