CLINICAL AND MOLECULAR GENETIC ANALYSIS OF BEST VITELLIFORM MACULAR DYSTROPHY

A novel compound heterozygous BEST1 gene mutation in two siblings causing autosomal recessive bestrophinopathy

PURPOSE

To describe the clinical features, imaging characteristics, and genetic test results associated with a novel compound heterozygous mutation of the BEST1 gene in two siblings with autosomal recessive bestrophinopathy.

METHODS

Two siblings underwent a complete ophthalmic examination, including dilated fundus examination, fundus photography, fundus autofluorescence imaging, spectral-domain optical coherence tomography, fluorescein angiography, electroretinography, and electrooculography. A clinical diagnosis of autosomal recessive bestrophinopathy was established based on ocular examination and multimodal retinal imaging. Subsequently, clinical exome sequencing consisting of a panel of 6670 genes was carried out to confirm the diagnosis and assess genetic alterations in the protein-coding region of the genome of the patients. The identified mutations were tested in the two affected siblings and one of their parents.

RESULTS

Two siblings (a 17-year-old female and a 15-year-old male) presented with reduced visual acuity and bilaterally symmetrical subretinal deposits of hyperautofluorescent materials in the posterior pole, which showed staining in the late phase of fluorescein angiogram. Spectral-domain optical coherence tomography demonstrated hyperreflective subretinal deposits and subretinal fluid accumulation. Both patients shared two mutations in the protein-coding region of the BEST1 gene, c.103G > A, p.(Glu35Lys) and c.313C > A, p.(Arg105Ser) (a novel disease-causing mutation). Sanger sequencing confirmed that the unaffected mother of the proband was carrying p.(Glu35Lys) variant in a heterozygous state.

CONCLUSIONS

We have identified and described the phenotype of a novel disease-causing mutation NM_004183.4:c.313C > A, p.(Arg105Ser) in a heterozygous state along with a previously reported mutation NM_004183.4:c.103G > A, p.(Glu35Lys) of the BEST1 gene in two related patients with autosomal recessive bestrophinopathy.

A pathogenic in-frame deletion-insertion variant in BEST1 phenocopies Stargardt disease

Here, we describe affected members of a 2-generation family with a Stargardt disease-like phenotype caused by a 2-base pair deletion insertion, c.1014_1015delGAinsCT;p.(Trp338_Asn339delinsCysTyr), in BEST1. The variant was identified by whole-exome sequencing, and its pathogenicity was verified through chloride channel recording using WT and transfected mutant HEK293 cells. Clinical examination of both patients revealed similar phenotypes at 2 different disease stages that were attributable to differences in their age at presentation. Hyperautofluorescent flecks along the arcades were observed in the proband, while the affected mother exhibited more advanced retinal pigment epithelium (RPE) loss in the central macula. Full-field electroretinogram testing was unremarkable in the daughter; however, moderate attenuation of generalized cone function was detected in the mother. Results from electrooculogram testing in the daughter were consistent with widespread dysfunction of the RPE characteristic of Best disease. Whole-cell patch-clamp recordings revealed a statistically significant decrease in chloride conductance of the mutant compared with WT cells. This report on a mother and daughter with a BEST1 genotype that phenocopies Stargardt disease broadens the clinical spectrum of BEST1-associated retinopathy.

Clinical and molecular findings in patients with pattern dystrophy

Purposes: To study the clinical and genetic background of a series of Italian patients affected by pattern dystrophy (PD).Methods: We reviewed patients with a clinical diagnosis of PD examined at the Eye Clinic in Florence from 2012 to 2019. We took into consideration patients with a standard ophthalmological examination, personal and familial ophthalmological history, fundus imaging, and molecular genetic analysis of genes PRPH2 and BEST1. We labelled patients with BEST1 and PRPH2 mutations as m-PD group (mutated) whereas patients with no mutations in these 2 genes as nm-PD group (non-mutated).Results: Seventy-seven PD patients were assessed (average age 59.7 ± 14.2, range 31-88 years). Fifty patients were placed in the nm-PD group and 27 in the m-PD. Pathogenic BEST1 and PRPH2 mutations were detected in 7% and 22% of PD patients, respectively. In total, we reported 1 BEST1 and 8 PRPH2 novel mutations. Ten patients were characterized by drusen in the nm-PD group whereas in no patients in the m-PD group drusen were detected at the fundus.Conclusions: An important proportion of patients affected by PD showed BEST1 or PRPH2 mutations. Patients affected by drusen represent a different sub-phenotype. Genetic examination is recommended for a correct clinical management.

SEROUS MACULAR DETACHMENT IN BEST DISEASE: A Masquerade Syndrome

PURPOSE

To describe the clinical and multimodal imaging findings of a series of cases of serous macular detachment (SMD) caused by Best disease (BD) masquerading as neovascular age-related macular degeneration or central serous chorioretinopathy that were inappropriately treated with intravitreal anti-vascular endothelial growth factor or laser therapy. This study will also present data to support age-related progressive choroidal thickening in BD patients, which may play a role in the development of SMD in this population.

METHODS

Clinical examination and multimodal imaging findings, including color fundus photography, spectral-domain optical coherence tomography, fundus autofluorescence, fluorescein angiography, and optical coherence tomography-angiography, were reviewed and analyzed. Subfoveal choroidal thickness was also formally measured, and an age-related choroidal thickness analysis was performed and compared with a normal population.

RESULTS

Twenty-six eyes of 13 patients (5 women) were included. Median age was 44 years. Nine patients presented with a history of SMD and subretinal fluid recalcitrant to various therapies, including intravitreal anti-vascular endothelial growth factor injections and photodynamic therapy. Best disease was subsequently diagnosed genetically in six patients and by detailed family history in seven. Mean logarithm of the minimum angle of resolution best-corrected visual acuity for all 26 eyes at last follow-up was +0.36 (Snellen equivalent of 20/46). Subfoveal choroidal thickness positively correlated with age for our cohort, increasing linearly at a rate of 25.6 µm per decade (R = 0.64; P < 0.001). Choroidal neovascularization was identified in four eyes on optical coherence tomography angiography, but these eyes did not respond to anti-vascular endothelial growth factor treatment.

CONCLUSION

The diagnosis of BD should be considered in patients presenting with SMD and recalcitrant subretinal fluid masquerading as neovascular age-related macular degeneration or chronic central serous chorioretinopathy to avoid unnecessary treatment procedures. The positive correlation of subfoveal choroidal thickness with age in BD patients may be a factor in the pathogenesis and development of SMD in this population. Recognizing the multimodal imaging features of SMD associated with BD, described in detail in this study, will guide practitioners to the accurate diagnosis of BD and reduce the risk of unnecessary intraocular procedures with potential complications.

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.

SHORT-TERM MODIFICATIONS OF ELLIPSOID ZONE IN BEST VITELLIFORM MACULAR DYSTROPHY

PURPOSE

To assess ellipsoid zone (EZ) alterations in Best vitelliform macular dystrophy using spectral-domain optical coherence tomography.

METHODS

Prospective, observational case series. Forty-three patients (43 eyes) underwent complete ophthalmological examination at baseline and at 24 months: best-corrected visual acuity (BCVA), biomicroscopy, fundus photography, and spectral-domain optical coherence tomography were performed. Acquisition protocol included 19-line raster scan. Alterations in EZ were marked on spectral-domain optical coherence tomography, and the area was manually calculated on a near-infrared reflectance image. Three patterns were identified: A (decrease >0.25 mm2), B (±0.25 mm2), and C (increase >0.25 mm2). Primary outcome was to describe different patterns of EZ alteration. Secondary outcomes included their correlation with BCVA and the description of a central optically preserved islet.

RESULTS

At baseline, altered EZ was identified in 40 eyes. Worse BCVA significantly correlated with larger EZ alterations but not with lesion extension on fundus photograph. Only "pattern-C" eyes unveiled BCVA worsening at follow-up. Optically preserved islet was detected in 16 eyes (37%), disclosing significantly better vision; its disappearance at follow-up (n = 7; 44% of 16 eyes) correlated with a decrease in BCVA.

CONCLUSION

The assessment of EZ status might represent a valuable functional marker in Best vitelliform macular dystrophy because stable alterations and the maintenance of a central optically preserved islet are associated with better visual acuity.

Serous business: Delineating the broad spectrum of diseases with subretinal fluid in the macula

A wide range of ocular diseases can present with serous subretinal fluid in the macula and therefore clinically mimic central serous chorioretinopathy (CSC). In this manuscript, we categorise the diseases and conditions that are part of the differential diagnosis into 12 main pathogenic subgroups: neovascular diseases, vitelliform lesions, inflammatory diseases, ocular tumours, haematological malignancies, paraneoplastic syndromes, genetic diseases, ocular developmental anomalies, medication-related conditions and toxicity-related diseases, rhegmatogenous retinal detachment and tractional retinal detachment, retinal vascular diseases, and miscellaneous diseases. In addition, we describe 2 new clinical pictures associated with macular subretinal fluid accumulation, namely serous maculopathy with absence of retinal pigment epithelium (SMARPE) and serous maculopathy due to aspecific choroidopathy (SMACH). Differentiating between these various diseases and CSC can be challenging, and obtaining the correct diagnosis can have immediate therapeutic and prognostic consequences. Here, we describe the key differential diagnostic features of each disease within this clinical spectrum, including representative case examples. Moreover, we discuss the pathogenesis of each disease in order to facilitate the differentiation from typical CSC.

Evidence of complement dysregulation in outer retina of Stargardt disease donor eyes

Stargardt macular degeneration (STGD) is a central blinding disease caused by loss of or dysfunctional ABCA4 transporter in both photoreceptors and retinal pigment epithelial (RPE) cells. Toxic bisretinoid-lipofuscin buildup in the RPE cells is a pathological hallmark of STGD patients and its mouse model, the Abca4^-/-. These vitamin A-derived fluorophores have been shown to induce oxidative stress, stimulate complement activity, and cause chronic inflammation of the RPE. In vivo modulation of complement regulatory pathway in the STGD mouse model has partially rescued the STGD phenotype suggesting that complement attack on the RPE is an important etiologic factor in disease pathogenesis. While bisretinoid-dependent complement activation was further evidenced in cultured RPE cells, this pathway has never been investigated directly in the context of RPE from STGD donor eyes. In the current study, we evaluate the complement reactivity in postmortem donor eyes of clinically diagnosed STGD patients. All three STGD donor eyes RPE displayed strong immunoreactivity for an antibody specific to 4-Hydroxynonenal, a lipid peroxidation byproduct. Also, unlike the control eyes, all three STGD donor eyes showed significantly increased membrane attack complex deposition on the RPE cells. In STGD eyes, increased MAC accumulation was mirrored by elevated C3 fragments internalized by the RPE and inversely correlated with the levels of complement factor H, a major complement regulatory protein. Here, we report the first direct evidence of RPE complement dysregulation as a causative factor in developing Stargardt phenotype.

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.

INTRARETINAL HYPERREFLECTIVE FOCI IN BEST VITELLIFORM MACULAR DYSTROPHY

PURPOSE

To report on the presence of hyperreflective foci (HF) on spectral domain optical coherence tomography in patients with Best vitelliform macular dystrophy (BVMD), and to describe the relationship between HF and stages of the disease.

METHODS

Consecutive patients diagnosed with BVMD were enrolled in a prospective cross-sectional study. All patients and control subjects underwent a complete ophthalmologic examination, including best-corrected visual acuity and spectral domain optical coherence tomography.

MAIN OUTCOME MEASURE

identification of HF in BVMD. Secondary outcome: assessment of the HF in each stage and correlation with best-corrected visual acuity.

RESULTS

Overall, 75 eyes of 39 patients were included in the study (Stage 1: 13%, Stage 2: 43%, Stage 3: 15%, Stage 4: 21%, and Stage 5: 8%). On spectral domain optical coherence tomography assessment, intraretinal HF were present in 83% of all eyes, in 91% of eyes affected by clinical BVMD (Stages 2-5) and in 100% of patients in Stages 4 and 5. In 46% of clinically diseased eyes, HF were localized in the fovea and in correspondence with the BVMD lesions at the level of the outer nuclear layer and outer plexiform layer. Hyperreflective foci were present in 16% of control eyes. Mean number of HF in eyes affected by clinical BVMD stood at 7.67 ± 7.35. These were predominantly small HF (6.23 ± 6.14, P < 0.001) localized in the outer nuclear layer (5.19 ± 5.38, P = 0.001) and presented largely in the extrafoveal, rather than the foveal area (5.21 ± 5.57 vs 2.46 ± 2.73, P = 0.001). Analysis of HF distribution revealed that the control group and Stage 1 eyes had the fewest HF; Stage 4 displayed a significant increase in the number of HF compared with Stages 2 and 3; Stage 5 also showed an increased number of HF, although this difference was statistically significant only with Stage 3 eyes. The best-corrected visual acuity was negatively related to the number of HF, with best-corrected visual acuity deteriorating as the number of HF increased in Stages 2 to 5 (P < 0.001).

CONCLUSION

This study describes the presence of HF in BVMD using spectral domain optical coherence tomography. Our data suggest that HF identification is correlated with the progression of the disease and could represent a useful biomarker of BVMD.

Choroidal Caverns: A Previously Unreported Optical Coherence Tomography Finding in Best Vitelliform Dystrophy

Best vitelliform macular dystrophy (VMD) is an autosomal dominant inherited dystrophy, most frequently caused by mutations in the BEST1 gene. The authors describe "choroidal caverns," a previously unreported optical coherence tomography finding in the choriocapillary and choroid of Best VMD. Histopathologic examination in eyes with Best VDM shows extensive deposition of lipofuscin in the retinal pigment epithelium (RPE) throughout the retina and accumulation of fibrillar material under the RPE and in the choroid. This supports the hypothesis that choroidal caverns could be a sign of the degenerative process involving the choroid in eyes with Best VMD. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:284-287.].

Clinical and Mutation Analysis of Patients with Best Vitelliform Macular Dystrophy or Autosomal Recessive Bestrophinopathy in Chinese Population

Mutations in the gene BEST1 usually cause bestrophinopathies, such as the rare progressive diseases Best vitelliform macular dystrophy (BVMD) and autosomal recessive bestrophinopathy (ARB). This study aimed to investigate the clinical characteristics of patients with BVMD or ARB carrying BEST1 mutations. A total of 12 probands including 9 patients with a clinical diagnosis of BVMD and 3 patients with a clinical diagnosis of ARB were recruited for genetics analysis. All patients underwent detailed ophthalmic examination. All coding exons of the BEST1 gene were screened by PCR-based DNA sequencing. Programs of PolyPhen-2, SIFT, and MutationTaster were used to analyze the potential pathogenicity of the mutations in BEST1. In the 9 unrelated patients with BVMD, one heterozygous BEST1 mutation was revealed in 8 patients and two compound heterozygous mutations in 1 patient. In the 3 unrelated patients with ARB, two compound heterozygous mutations were revealed in 2 patients and three compound heterozygous mutations in 1 patient. Molecular analyses identified a total of 15 mutations, including 3 novel mutations (c.424A>G p.S142G, c.436G>A p.A146T, and c.155T>C p.L52P). Antivascular endothelial growth factor (VEGF) drugs were given to two affected eyes, especially those also exhibiting choroidal neovascularization (CNV), and no serious adverse events occurred. Our study indicates that there is wide genotypic and phenotypic variability in patients with BVMD or ARB in China. The screening of BEST1 gene is significant for the precise diagnosis of BVMD and ARB.

SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY FEATURES IN DIFFERENT STAGES OF BEST VITELLIFORM MACULAR DYSTROPHY

PURPOSE

To provide a systematic classification of findings regarding the different stages of vitelliform macular dystrophy on spectral domain optical coherence tomography (SD-OCT).

METHODS

Ninety-four eyes of 47 patients were recruited in a prospective cross-sectional study. All patients underwent a complete ophthalmologic examination, including best-corrected visual acuity using Early Treatment Diabetic Retinopathy Study (ETDRS) charts, biomicroscopy, and SD-OCT. The findings assessed included vitelliform material, neurosensory detachment, status of external limiting membrane, ellipsoid zone and retinal pigment epithelium, choroidal excavation, foveal cavitation, choroidal neovascularization, vitreomacular traction, and macular hole. The primary outcome measure was the identification of SD-OCT findings in each vitelliform macular dystrophy stage. Secondary outcomes included the correlations between SD-OCT features and visual acuity changes.

RESULTS

The outer retinal layers (external limiting membrane, ellipsoid zone, and retinal pigment epithelium) were found to be more commonly disrupted in Stages 2 to 4 (range: 86%-100%), whereas their absence was more typical of Stage 5 (71%-86%). Vitelliform material was found in 100% of Stages 2 and 3, 93% of Stage 4, and interestingly in 43% of Stage 5. Eyes characterized by vitelliform material showed a greater correlation with higher best-corrected visual acuity than eyes without it (0.35 logarithm of the minimum angle of resolution vs. 0.80 ± 0.36 logarithm of the minimum angle of resolution, approximately 20/45 and 20/125 Snellen equivalent, respectively) (t = 3.726, P < 0.05). Moreover, its absence was associated with a best-corrected visual acuity of 0.5 logarithm of the minimum angle of resolution or worse (approximately 20/63 Snellen equivalent; P < 0.05). Subretinal fluid was more common in Stages 3 and 4 (72.7% and 75%, respectively) than Stages 2 and 5 (P = 0.004). Eyes with subretinal fluid were significantly associated with a visual acuity of 0.2 logarithm of the minimum angle of resolution or worse (approximately 20/32 Snellen equivalent; P = 0.04).

CONCLUSION

Spectral domain optical coherence tomography assessment primarily indicates an outer retinal layer disruption in Stages 2 to 4, along with the presence of vitelliform material extending into the more advanced clinical stages too. Eyes characterized by the persistence of vitelliform material show better best-corrected visual acuity. Future investigations based on a longitudinal follow-up are warranted to correlate SD-OCT modifications with functional responses to identify SD-OCT indicators for prognostic and therapeutic purposes.

Next generation sequencing identifies novel disease-associated BEST1 mutations in Bestrophinopathy patients

Bestinopathies are a spectrum of retinal disorders associated with mutations in BEST1 including autosomal recessive bestrophinopathy (ARB) and autosomal dominant Best vitelliform macular dystrophy (BVMD). We applied whole-exome sequencing on four unrelated Indian families comprising eight affected and twelve unaffected individuals. We identified five mutations in BEST1, including p.Tyr131Cys in family A, p.Arg150Pro in family B, p.Arg47His and p.Val216Ile in family C and p.Thr91Ile in family D. Among these, p.Tyr131Cys, p.Arg150Pro and p.Val216Ile have not been previously reported. Further, the inheritance pattern of BEST1 mutations in the families confirmed the diagnosis of ARB in probands in families A, B and C, while the inheritance of heterozygous BEST1 mutation in family D (p.Thr91Ile) was suggestive of BVMD. Interestingly, the ARB families A and B carry homozygous mutations while family C was a compound heterozygote with a mutation in an alternate BEST1 transcript isoform, highlighting a role for alternate BEST1 transcripts in bestrophinopathy. In the BVMD family D, the heterozygous BEST1 mutation found in the proband was also found in the asymptomatic parent, suggesting an incomplete penetrance and/or the presence of additional genetic modifiers. Our report expands the list of pathogenic BEST1 genotypes and the associated clinical diagnosis.

Multifocal Best's disease: The importance of genetic tests

OBJECTIVES AND METHODS

Our objective is to describe a multifocal vitelliform presentation of Best's disease. The lesions in this disease may vary in size and shape, some may be a disc diameter in size, and often have some irregularity in their contour. The case is described of a 21-year-old male patient referred to our ophthalmology department due to a progressive loss of vision. His poor visual acuity was confirmed, and a complete examination was performed, in which macular flecks were observed, with yellow pigment arranged in oval distribution near their periphery. Due to the suspicion of Best's multifocal disease, genetic tests were performed. Multifocal vitelliform disease with the same features as those in Best's disease occurs most frequently in patients with a normal electro-oculogram (EOG), and a normal family history.

CONCLUSION

Best's multifocal disease must be suspected in case of multiple vitelliruptive lesions close to the posterior pole. Genetic testing is essential for its diagnosis.

Bestrophinopathy: An RPE-photoreceptor interface disease

Bestrophinopathies, one of the most common forms of inherited macular degenerations, are caused by mutations in the BEST1 gene expressed in the retinal pigment epithelium (RPE). Both human and canine BEST1-linked maculopathies are characterized by abnormal accumulation of autofluorescent material within RPE cells and bilateral macular or multifocal lesions; however, the specific mechanism leading to the formation of these lesions remains unclear. We now provide an overview of the current state of knowledge on the molecular pathology of bestrophinopathies, and explore factors promoting formation of RPE-neuroretinal separations, using the first spontaneous animal model of BEST1-associated retinopathies, canine Best (cBest). Here, we characterize the nature of the autofluorescent RPE cell inclusions and report matching spectral signatures of RPE-associated fluorophores between human and canine retinae, indicating an analogous composition of endogenous RPE deposits in Best Vitelliform Macular Dystrophy (BVMD) patients and its canine disease model. This study also exposes a range of biochemical and structural abnormalities at the RPE-photoreceptor interface related to the impaired cone-associated microvillar ensheathment and compromised insoluble interphotoreceptor matrix (IPM), the major pathological culprits responsible for weakening of the RPE-neuroretina interactions, and consequently, formation of vitelliform lesions. These salient alterations detected at the RPE apical domain in cBest as well as in BVMD- and ARB-hiPSC-RPE model systems provide novel insights into the pathological mechanism of BEST1-linked disorders that will allow for development of critical outcome measures guiding therapeutic strategies for bestrophinopathies.

Juvenile Macular Degenerations

In this article, we review the following 3 common juvenile macular degenerations: Stargardt disease, X-linked retinoschisis, and Best vitelliform macular dystrophy. These are inherited disorders that typically present during childhood, when vision is still developing. They are sufficiently common that they should be included in the differential diagnosis of visual loss in pediatric patients. Diagnosis is secured by a combination of clinical findings, optical coherence tomography imaging, and genetic testing. Early diagnosis promotes optimal management. Although there is currently no definitive cure for these conditions, therapeutic modalities under investigation include pharmacologic treatment, gene therapy, and stem cell transplantation.

Optical coherence tomography in Best vitelliform macular dystrophy

PURPOSE

To analyze spectral-domain optical coherence tomography (SD-OCT)-specific findings in the different stages of vitelliform macular dystrophy (VMD).

METHODS

Thirty-seven patients were prospectively recruited. All the patients underwent a complete ophthalmologic examination, including best-corrected visual acuity (BCVA), biomicroscopy, and SD-OCT. The examined findings were vitelliform material, neurosensory detachment, intraretinal hyperreflective foci, and the status of external limiting membrane, ellipsoid zone, and retinal pigment epithelium. The primary outcome was the stratification of SD-OCT findings in each VMD stage. Secondary outcomes included the description of different characteristics related to intraretinal hyperreflective foci.

RESULTS

Outer retinal layers were preserved almost exclusively in stage 1 (range 70%-100%), whereas their disruption and absence were typical of stages 2 to 4 (83%-100%) and stage 5 (67%-83%), respectively. Vitelliform material was found always in stages 2 and 3, 89% of stage 4, and rarely in stage 5 (33%). Neurosensory detachment was to some extent representative of stages 3 and 4 (80% and 72%, respectively) when compared with the other stages (p<0.001). Hyperreflective foci (16% of all eyes) demonstrated a progressive increase across stages 2 to 4, with slightly reduced figure in stage 5. These foci were located in the outer nuclear and plexiform layers, showed different sizes, and were not associated with a visual acuity reduction (p = 0.64).

CONCLUSIONS

A progressive deterioration of the outer retinal layers was noticeable in more advanced stages of VMD. The reduction of vitelliform material from stage 3 to 4 was paralleled by an increased evidence of neurosensory detachment. Although showing different size and location, hyperreflective foci did not correlate with worse BCVA.

Flat Anterior Chamber after Trabeculectomy in Secondary Angle-Closure Glaucoma with BEST1 Gene Mutation: Case Series

Purpose

Trabeculectomy has been regarded as a mainstay of initial treatment in eyes of angle closure glaucoma (ACG) with peripheral anterior synechia > 180° in the Chinese population while its efficacy in secondary ACG with BEST1 gene mutation remains unclear. We set out to investigate the treatment outcome of trabeculectomy for secondary ACG in a group of patients with autosomal recessive bestrophinopathy (ARB).

Methods

In this retrospective case series study, 8 secondary ACG patients with ARB and their 4 recruited family members underwent a thorough ophthalmic examination including best-corrected visual acuity, Goldmann applanation tonometry, gonioscopy, and fundus examinations. Ultrasound biomicroscopy, optical coherence tomography (OCT), ultrasound A-scan, B-scan, electro-oculography (EOG), Humphrey perimetry, fundus photography, fundus fluorescein angiography (FFA) and indocyanine green angiography (ICGA) were also performed. Blood samples were obtained in the patients and their available family members to analyze the variants of the BEST1 gene. Trabeculectomy was performed in the 8 patients (15 eyes).

Results

The age of onset varied from 13 to 38 years. The average axial length (AL) of the affected eyes was 21.82 ± 0.92 mm and the average anterior chamber depth (ACD) was 2.19 ± 0.29 mm. There was marked axial shallowing of the anterior chamber in all 15 eyes after trabeculectomy, and was not improved with potent mydriatics. The IOP was elevated in 3 eyes. Variable degree of yellowish subretinal deposits was observed in the posterior retina. The FFA showed punctuate or patched hyperfluorescence suggesting retinal pigment epithelium impairment. The ICGA demonstrated dilatation of choroidal vessels. The OCT revealed diffused neuroretinal detachment in the posterior and midperipheral retina, with intraretinal fluid collections, and hyperreflective subretinal accumulations. The average subfoveal choroidal thickness of the patients was 382.36 ± 80.09 μm. All the patients and enrolled family members carried mutation in BEST1 gene.

Conclusions

ARB is a rare condition with fundus manifestations mimicking various diseases. Careful discrimination should be taken to exclude any secondary causes for ACG before treatment. Concerning the high incidence of postoperative shallow anterior chamber, selection of filtering surgery should be very careful in these patients.

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.

Long-Term Macular Changes in the First Proband of Autosomal Dominant Vitreoretinochoroidopathy (ADVIRC) Due to a Newly Identified Mutation in BEST1

BACKGROUND

Mutations in BEST1 account for autosomal dominant vitreoretinochoroidopathy (ADVIRC), a rare inherited retinal dystrophy with presenile cataracts and incomplete anterior segment development. The long-term clinical findings and visual prognosis of these patients continues to evolve over time.

MATERIALS AND METHODS

The retina was assessed by fundus photography, fluorescein angiography, and spectral domain optical coherence tomography. Sanger dideoxy chain-termination sequencing identified mutations in BEST1. Bioinformatic tools were used to predict changes in splicing. An in vitro splicing assay was applied to evaluate for altered pre-mRNA splicing.

RESULTS

Long-term follow up of the first ever reported ADVIRC proband revealed progressive foveal atrophy in both eyes 3 decades after his initial presentation. Progressive retinal ischemia, bilateral iris atrophy, and pseudophakodnesis were observed on follow up. The patient was heterozygous for a c.248G > A missense mutation in exon 4 of BEST1, affecting a highly conserved transmembrane domain. Although computational prediction models suggest a change in the binding probability of splicing-associated SR proteins, in vitro splicing assays failed to demonstrate an effect of the c.248G > A mutation on splicing of BEST1 exon 3 or exon 4.

CONCLUSIONS

Progressive posterior chorioretinal changes occurred over time in the initial ADVIRC proband, leading to visual loss. The causative mutation in this patient falls in the transmembrane domain of the BEST1 protein, with unclear functional consequences. Although previous studies showed alteration in pre-mRNA splicing, in vitro splicing assays failed to demonstrate this in our patient.

Two novel mutations in the bestrophin-1 gene and associated clinical observations in patients with best vitelliform macular dystrophy

The purpose of the current study was to investigate the 11 bestrophin-1 (BEST1) exons in patients with best vitelliform macular dystrophy (BVMD), and to characterize the associated clinical features. Complete ophthalmic examinations were conducted on two families, and two family members were diagnosed with BVMD. Genomic DNA was extracted from the leukocytes of peripheral blood collected from the patients and their family members, in addition to 100 unrelated control subjects recruited from the same population. The polymerase chain reaction was used to amplify a total of 11 exons of the BEST1 gene, which were directly sequenced. Ophthalmic examinations, including best-corrected visual acuity, slit-lamp examination, fundus examination, fundus photography and fluorescein angiography imaging, as well as anterior segment analysis with Pentacam and optical coherence tomography, were conducted. The patients exhibited yellowish lesions in the macular area. A heterozygous mutation c.910_912delGAT (p.304del Asp) in exon 7 was identified in Case 1. A heterozygous BEST1 missense mutation c.685T>G (p.Trp229Gly) in exon 5 was identified in Case 2, but not in any of the unaffected family members or normal controls. Although BEST1 gene mutations and polymorphisms have previously been reported in various ethnic groups, the current study identified, for the first time to the best of our knowledge, two novel BEST1 gene mutations in patients with BVMD.

Best vitelliform macular dystrophy: literature review

Best vitelliform macular dystrophy (BVD) is a slowly progressive form of macular dystrophy. In most cases this disease begins in childhood although sometimes it can develop in later age. The diagnosis of BVD is based on family history, clinical and electrophysiological findings. Clinical signs are variable, yet the majority of patients have a typical yellow yolk-like macular lesion in the eye fundus. Lesions are usually bilateral, but in rare cases can be unilateral. Atrophy of the macula may develop after many years. The mutations responsible for Best vitelliform macular dystrophy are found in a gene called VMD2, which encodes a transmembrane protein named bestrophin-1 (hBest1) that is a Ca2+-sensitive chloride channel. Most reported cases causing the disease are in exons 2, 4, 6 and 8 in patients with BVD. In this article we discuss the etiology of Best’s vitelliform macular dystrophy, clinical presentation, diagnostics, genetic and current treatment possibilities.

Juvenile-onset macular degeneration and allied disorders

While age-related macular degeneration (AMD) is a leading cause of central vision loss among the elderly, many inherited diseases that present earlier in life share features of AMD. These diseases of juvenile-onset macular degeneration include Stargardt disease, Best disease, retinitis pigmentosa, X-linked retinoschisis, and other allied disorders. In particular, they can be accompanied by the appearance of drusen, geographic atrophy, macular hyperpigmentation, choroidal neovascularization, and disciform scarring just as in AMD, and often may be confused for the adult form of the disease. Diagnosis based on funduscopic findings alone can be challenging. However, the use of diagnostic studies such as electroretinography, electrooculography, optical coherence tomography, and fundus autofluorescence in conjunction with genetic testing can lead to an accurate diagnosis.

Best's vitelliform macular dystrophy in 10- and 31-month-old siblings

There are limited reports of Best's disease in children younger than 3 years. This is a case series of two family members aged 10 and 31 months with Best's disease. To the authors' knowledge, the 10-month-old male infant is the youngest patient with Best's disease documented by fundus photography.

Best disease presenting as a giant serous pigment epithelial detachment

PURPOSE

To report a case of Best disease presenting as a giant serous pigment epithelial detachment and misdiagnosed as central serous chorioretinopathy.

METHODS

Clinical examination and multimodal imaging, including color fundus photography, fluorescein angiography, fundus autofluorescence, and spectral domain optical coherence tomography are presented, as well as the results of electrooculography.

RESULTS

A 54-year-old Asian man underwent photodynamic therapy for a large serous pigment epithelial detachment presumed to be due to central serous chorioretinopathy. When the lesion was recalcitrant to therapy, further investigation revealed severely decreased Arden ratios consistent with Best disease.

CONCLUSION

There is a wide spectrum in the clinical presentation of Best disease. Diagnostic uncertainty can be elucidated with fundus autofluorescence, spectral domain optical coherence tomography imaging, electrooculography, and genetic testing.

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.

Molecular consequences of BEST1 gene mutations in canine multifocal retinopathy predict functional implications for human bestrophinopathies

PURPOSE

Bestrophin-1 gene (BEST1) mutations are responsible for a broad spectrum of human retinal phenotypes, jointly called bestrophinopathies. Canine multifocal retinopathy (cmr), caused by mutations in the dog gene ortholog, shares numerous phenotypic features with human BEST1-associated disorders. The purpose of this study was the assessment of molecular consequences and pathogenic outcomes of the cmr1 (C(73)T/R(25)X) premature termination and the cmr2 (G(482)A/G(161)D) missense mutation of the canine model compared with the C(87)G/Y(29)X mutation observed in human patients.

METHODS

Dogs carrying the BEST1 mutation were introduced into a breeding colony and used to produce either carrier or affected offspring. Eyes were collected immediately after euthanatization at the disease-relevant ages and were harvested for expression studies. In parallel, an in vitro cell culture model system was developed and compared with in vivo

RESULTS

RESULTS

The results demonstrate that cmr1 and human C(87)G-mutated transcripts bypass the nonsense-mediated mRNA decay machinery, suggesting the AUG proximity effect as an underlying transcriptional mechanism. The truncated protein, however, is not detectable in either species. The in vitro model accurately recapitulates transcriptional and translational expression events observed in vivo and, thus, implies loss of bestrophin-1 function in cmr1-dogs and Y(29)X-affected patients. Immunofluorescence microscopy of cmr2 mutant showed mislocalization of the protein.

CONCLUSIONS

Molecular evaluation of cmr mutations in vivo and in vitro constitutes the next step toward elucidating genotype-phenotype interactions concerning human bestrophinopathies and emphasizes the importance of the canine models for studying the complexity of the BEST1 disease mechanism.

Systematic screening of BEST1 and PRPH2 in juvenile and adult vitelliform macular dystrophies: a rationale for molecular analysis

PURPOSE

To evaluate a genetic approach of BEST1 and PRPH2 screening according to age of onset, family history, and Arden ratio in patients with juvenile vitelliform macular dystrophy (VMD2) or adult-onset vitelliform macular dystrophy (AVMD), which are characterized by autofluorescent deposits.

DESIGN

Clinical, electrophysiologic, and molecular retrospective study.

PARTICIPANTS

The database of a clinic specialized in genetic sensory diseases was screened for patients with macular vitelliform dystrophy. Patients with an age of onset less than 40 years were included in the VMD2 group (25 unrelated patients), and patients with an age of onset more than 40 years were included in the AVMD group (19 unrelated patients).

METHODS

Clinical, fundus photography, and electro-oculogram (EOG) findings were reviewed. Mutation screening of BEST1 and PRPH2 genes was systematically performed.

MAIN OUTCOME MEASURES

Relevance of age of onset, family history, and Arden ratio were reviewed.

RESULTS

Patients with VMD2 carried a BEST1 mutation in 60% of the cases. Seven novel mutations in BEST1 (p.V9L, p.F80V, p.I73V, p.R130S, pF298C, pD302A, and p.179delN) were found. Patients with VMD2 with a positive family history or a reduced Arden ratio carried a BEST1 mutation in 70.5% of cases and in 83% if both criteria were fulfilled. Patients with AVMD carried a PRPH2 mutation in 10.5% of cases and did not carry a BEST1 mutation. The probability of finding a PRPH2 mutation increased in the case of a family history (2/5 patients). Electro-oculogram was normal in 3 of 15 patients with BEST1 mutations and reduced in the 3 patients with PRPH2 mutations.

CONCLUSIONS

Age of onset is a major criterion to distinguish VMD2 from AVMD. Electro-oculogram is not as relevant because decreased or normal Arden ratios have been associated with mutations in both genes and diseases. A positive family history increased the probability of finding a mutation. BEST1 screening should be recommended to patients with an age of onset less than 40 years, and PRPH2 screening should be recommended to patients with an age of onset more than 40 years. For an onset between 30 and 40 years, PRPH2 can be screened if no mutation has been detected in BEST1.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

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.

Novel and homozygous BEST1 mutations in Chinese patients with Best vitelliform macular dystrophy

PURPOSE

The purpose of this study was to investigate the BEST1 gene mutations in Chinese patients with Best vitelliform macular dystrophy (BVMD).

METHODS

Twenty-six subjects from 7 Chinese families with BVMD and 100 unrelated healthy Chinese subjects without a family history of BVMD were screened for mutations in the BEST1 gene by direct sequencing. The subjects underwent complete ophthalmologic examination and BEST1 gene screening.

RESULTS

Six novel missense mutations (Thr2Asn, Leu75Phe, Ser144Asn, Arg255Trp, Pro297Thr, and Asp301Gly) and 1 previously reported mutation (Arg218Cys) were identified. Each family was found to have a unique BEST1 mutation that segregated with the disease. Two of the six novel mutations are located within the four previously reported common mutation clusters within the BEST1 gene. One family with patients having homozygous Leu75Phe mutations did not have the more severe BVMD phenotype. None of the patients with mutations was identified among the 100 healthy control subjects.

CONCLUSION

A large number of unique novel missense mutations was found in Chinese patients with BVMD, suggesting considerable interethnic differences between the mutation sites in the BEST1 gene in different populations. The few truncating BEST1 mutations and the lack of a more severe phenotype in homozygous patients suggest that the missense BEST1 mutation may produce a dominant negative effect on wild-type BEST1 gene.

Multimodal fundus imaging in Best vitelliform macular dystrophy

BACKGROUND

Best vitelliform macular dystrophy (BVMD) is a rare autosomal dominant retinal disease of highly variable phenotypic expression. Interpretations of disease mechanisms based on histopathology, electrophysiology, genetic analysis, and retinal imaging are somewhat discordant in fundamental issues such as the location and extension of primary retinal changes. Herein we describe the morphological macular features in patients with BVMD undergoing simultaneous multimodal fundus imaging and compare to those of normal age-matched subjects.

METHODS

Comparative study including seven patients with BVMD (14 eyes) and seven age-matched healthy subjects (14 eyes). All participants were submitted to complete ophthalmological examination, fundus photography, and standardized multimodal fundus imaging protocol including Fourier-domain optical coherence tomography (Fd-OCT) combined with near-infrared reflectance and blue-light fundus autofluorescence (FAF).

RESULTS

In two eyes in the "subclinical" stage, Fd-OCT revealed thickening of the middle highly reflective layer (HRL) localized between the photoreceptors' inner/outer segments junction (inner-HRL) and RPE/Bruch's membrane reflective complex (outer-HRL) throughout the macula. In one eye in the "vitelliform" stage, a homogeneous hyper-reflective material on Fd-OCT was observed between the middle-HRL and outer-HRL; this material presented increased fluorescence on FAF. The outer nuclear layer (ONL) was thinned in the central macula and subretinal fluid was not identified in these earlier disease stages. In patients of "pseudohypopyon" (two eyes), "vitelliruptive" (eight eyes) and "atrophic" (one eye) stages, Fd-OCT revealed a variety of changes in the middle- and inner-HRLs and thinning of ONL. These changes were found to be associated with the level of visual acuity observed. Thickening of the middle-HRL was observed beyond the limits of the clinically evident macular lesion in all eyes.

CONCLUSIONS

Multimodal fundus imaging demonstrated thickening of the reflective layer corresponding to the photoreceptors' outer segments throughout the macula with no subretinal fluid accumulation as the earliest detectable feature in BVMD. Changes detected in the photoreceptors' reflective layers (middle- and inner- HRLs) and ONL thinning seemed to be progressive with direct implications for the level of visual acuity impairment observed among the different stages of the disease.