ANATOMICAL AND FUNCTIONAL OUTCOMES OF BEVACIZUMAB TREATMENT IN PEDIATRIC AUTOSOMAL RECESSIVE BESTROPHINOPATHY

PURPOSE

The purpose of this study was to report functional and anatomical outcomes of anti-VEGF treatment in eyes with autosomal recessive bestrophinopathy (ARB) presenting in the first decade of life.

METHODS

The study included case series of four eyes from two siblings with compound heterozygous mutations in the BEST1 gene who were treated with eight monthly intravitreal bevacizumab injections. Response to treatment was analyzed using color fundus photography, fundus autofluorescence, optical coherence tomography, OCT angiography, and microperimetry.

RESULTS

Patient 1 (male, age 9 years) had visual acuity of 20/20 in the right eye and 20/50 in the left eye. Patient 2 (female, age 10 years) had visual acuity of 20/25 in the right eye and 20/20 in the left eye. All eyes had multifocal subretinal deposition of lipofuscin and subretinal fluid, and three eyes had choroidal neovascularization (CNV). Lipofuscin material reabsorbed in 2 of 4 eyes, the CNV regressed in 3 of 3 eyes, a bacillary detachment resolved in 1 of 1 eye, but the subretinal fluid did not change. Functional improvement in visual acuity was noted, but MP showed scattered areas of reduced retinal sensitivity. No ocular or systemic side effects were detected.

CONCLUSION

Anti-VEGF treatment of choroidal neovascularization in eyes with ARB resulted in anatomical changes that were only clinically significant in the eye with decreased visual acuity. The hyporeflective subretinal material remained unchanged suggesting a nonexudative cause. These findings provide new insights into the management of ARB, especially in pediatric subjects with CNV.

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.

Non-vasogenic cystoid maculopathy in autosomal recessive bestrophinopathy: novel insights from NIR-FAF and OCTA imaging

BACKGROUND

Autosomal Recessive Bestrophinopathy (ARB) is an inherited retinal disease caused by biallelic mutations in the BEST1 gene. Herein, we report the multimodal imaging findings of ARB presenting with cystoid maculopathy and investigate the short-term response to combined systemic and topical carbonic anhydrase inhibitors (CAIs).

MATERIAL AND METHODS

An observational, prospective, case series on two siblings affected by ARB is presented. Patients underwent genetic testing and optical coherence tomography (OCT), blue-light fundus autofluorescence (BL-FAF), near-infrared fundus autofluorescence (NIR-FAF), fluorescein angiography (FA), MultiColor imaging, and OCT angiography (OCTA).

RESULTS

Two male siblings, aged 22 and 16, affected by ARB resulting from c.598C>T, p.(Arg200*) and c.728C>A, p.(Ala243Glu) BEST1 compound heterozygous variants, presented with bilateral multifocal yellowish pigment deposits scattered through the posterior pole that corresponded to hyperautofluorescent deposits on BL-FAF. Vice versa, NIR-FAF mainly disclosed wide hypoautofluorescent areas in the macula. A cystoid maculopathy and shallow subretinal fluid were evident on structural OCT, albeit without evidence of dye leakage or pooling on FA. OCTA demonstrated disruption of the choriocapillaris throughout the posterior pole and sparing of intraretinal capillary plexuses. Six months of combined therapy with oral acetazolamide and topical brinzolamide resulted in limited clinical benefit.

CONCLUSIONS

We reported two siblings affected by ARB, presenting as non-vasogenic cystoid maculopathy. Prominent alteration of NIR-FAF signal and concomitant choriocapillaris rarefaction on OCTA were noted in the macula. The limited short-term response to combined systemic and topical CAIs might be explained by the impairment of the RPE-CC complex.

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.

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.

Novel BEST1 mutations and clinical characteristics of autosomal recessive bestrophinopathy in a Spanish patient

PURPOSE

To describe the clinical and genetic characteristics (novel mutation in BEST1 gene) of a Spanish patient with autosomal recessive bestrophinopathy (ARB).

METHODS

The detailed ophthalmological examination included best corrected visual acuity (BCVA), color and autofluorescence photography, fluorescein angiography, optical coherence tomography, and electrophysiology tests. A next-generation sequencing (NGS) strategy was applied to the index patient, and then sequenced in an Illumina NextSeq500 system.

RESULTS

A 55-year-old male presented with a BCVA of 20/25 in the right eye and 20/20 in the left eye. Fundoscopy revealed perifoveal yellow flecked-like lesions. Fluorescein angiography and fundus autofluorescence results were consistent with pattern dystrophy. A homozygous frameshift mutation in BEST1 (c.341_342del; p.(Leu114Glnfs*57)) was identified as the cause of the disease.

CONCLUSION

ARB is a genetic disease that leads to irreversible visual loss. In this report we found a novel mutation responsible for this disease.

Mutation-Dependent Pathomechanisms Determine the Phenotype in the Bestrophinopathies

Best vitelliform macular dystrophy (BD), autosomal dominant vitreoretinochoroidopathy (ADVIRC), and the autosomal recessive bestrophinopathy (ARB), together known as the bestrophinopathies, are caused by mutations in the bestrophin-1 (BEST1) gene affecting anion transport through the plasma membrane of the retinal pigment epithelium (RPE). To date, while no treatment exists a better understanding of BEST1-related pathogenesis may help to define therapeutic targets. Here, we systematically characterize functional consequences of mutant BEST1 in thirteen RPE patient cell lines differentiated from human induced pluripotent stem cells (hiPSCs). Both BD and ARB hiPSC-RPEs display a strong reduction of BEST1-mediated anion transport function compared to control, while ADVIRC mutations trigger an increased anion permeability suggesting a stabilized open state condition of channel gating. Furthermore, BD and ARB hiPSC-RPEs differ by the degree of mutant protein turnover and by the site of subcellular protein quality control with adverse effects on lysosomal pH only in the BD-related cell lines. The latter finding is consistent with an altered processing of catalytic enzymes in the lysosomes. The present study provides a deeper insight into distinct molecular mechanisms of the three bestrophinopathies facilitating functional categorization of the more than 300 known BEST1 mutations that result into the distinct retinal phenotypes.

Diffuse Outer Layer Opacification: A Novel Finding in Patients With Autosomal Recessive Bestrophinopathy

PURPOSE

Autosomal recessive bestrophinopathy (ARB) is a rare inherited retinal dystrophy resulted from mutations in bestrophin-1 (BEST1) which affect functioning of the retinal pigment epithelium (RPE). Descriptions of disease findings in patients with ARB to date have focused only on macular changes. In this case series, we report previously undescribed mid-peripheral retinal changes occurring in 4 patients with ARB.

DESIGN

Case series.

METHODS

A single-center, retrospective review of medical records from Mayo Clinic patients with ARB was performed. Imaging reviewed include fundus photography, fundus autofluorescence, spectral domain optical coherence tomography (OCT), and fluorescein angiography. Demographic information and disease progression were noted.

RESULTS

4 affected patients from 3 families were identified. All 4 patients were female, and mean age was 12.5 years (range 5-19 years). Diffuse mid-peripheral whitening was consistently noted on fundus photography. Concomitant OCT imaging demonstrated areas of hyperreflectivity in the photoreceptor outer segment layer in areas corresponding to whitening seen on fundus photography. In 1 patient who was followed for 12 years, this finding persisted. Subretinal fluid was also consistently present. Other pathologic imaging findings observed in each patient were in agreement with previous reports of ARB.

CONCLUSIONS

This is the first descriptive report of pathologic findings occurred beyond the posterior pole in patients with ARB. These mid-peripheral retinal changes potentially imply that the entirety of the RPE is affected by mutations in BEST1, as also suggested by previous electro-oculogram (EOG) findings. Such implications will be important when developing treatment trials, as past trials have focused only on the posterior pole of the RPE.

Novel BEST1 gene mutations associated with two different forms of macular dystrophy in Tunisian families

BACKGROUND

Epidemiological studies of hereditary eye diseases allowed us to identify two Tunisian families suffering from macular dystrophies: Best vitelliform macular dystrophy (BVMD) and autosomal recessive bestrophinopathy (ARB). The purpose of the current study was to investigate the clinical characteristics and the underlying genetics of these two forms of macular dystrophy.

METHODS

Complete ophthalmic examination was performed including optical coherence tomography, electroretinography, electrooculography and autofluoresence imaging in all patients. Genomic DNA was extracted from peripheral blood collected from patients and family members.

RESULTS

Sanger sequencing of all exons of the BEST1 gene in both families identified two new mutations: a missense mutation c.C91A [p.L31 M] at the N-terminal transmembrane domain within the ARB family and a nonsense mutation C1550G (p.S517X) in the C-terminal domain segregating in the BVMD family.

CONCLUSIONS

Several mutations of the BEST1 gene have been reported which are responsible for numerous ocular pathologies. To the best of our knowledge, it is the first time we report mutations in this gene in Tunisian families presenting different forms of macular dystrophy. Our report also expands the list of pathogenic BEST1 genotypes and the associated clinical diagnosis.

Novel Missense Mutations in BEST1 Are Associated with Bestrophinopathies in Lebanese Patients

To identify Bestrophin 1 (BEST1) causative mutations in six Lebanese patients from three families, of whom four had a presumed clinical diagnosis of autosomal recessive bestrophinopathy (ARB) and two showed a phenotype with a single vitelliform lesion, patients were subjected to standard ophthalmic examinations. In addition, BEST1 exons and their flanking regions were amplified and sequenced by Sanger sequencing. Co-segregation and detailed bio-informatic analyses were performed. Clinical examination results were consistent with ARB diagnosis for all index patients showing multifocal vitelliform lesions and a markedly reduced light peak in the electrooculogram, including the two patients with a single vitelliform lesion. In all cases, most likely disease-causing BEST1 mutations co-segregated with the phenotype. The ARB cases showed homozygous missense variants (M1, c.209A>G, p.(Asp70Gly) in exon 3, M2, c.1403C>T; p.(Pro468Leu) in exon 10 and M3, c.830C>T, p.(Thr277Met) in exon 7), while the two patients with a single vitelliform lesion were compound heterozygous for M1 and M2. To our knowledge, this is the first study describing mutations in Lebanese patients with bestrophinopathy, where novel biallelic BEST1 mutations associated with two phenotypes were identified. Homozygous mutations were associated with multifocal lesions, subretinal fluid, and intraretinal cysts, whereas compound heterozygous ones were responsible for a single macular vitelliform lesion.