Autosomal dominant vitreoretinochoroidopathy (ADVIRC)

Variable expressivity of the autosomal dominant vitreoretinochoroidopathy (ADVIRC) phenotype associated with a novel variant in BEST1

BACKGROUND

This case report explores the relationship between genetics and phenotypic variability in autosomal dominant vitreoretinochoroidopathy (ADVIRC). The study focuses on a case presenting a novel mutation in the BEST1 gene and its phenotype in the case's relatives, shedding light on the structural and functional intricacies underlying this rare ophthalmologic disorder.

CASE PRESENTATION

A 33-year-old female presented for consultation with a history of bilateral retinal damage accompanied by a complaint of decreased visual acuity, progressive visual field deficit, and night blindness over the past year. Ophthalmic examination revealed a distinctive phenotype, including fibrillar vitreous, pigmented cells, and atrophic hyperpigmented retina in the periphery which was suggestive of a diagnosis of ADVIRC. Genetic testing revealed a heterozygous c.1101-1 G>T variant in BEST1, a novel splice site mutation. Functional analysis confirmed its impact on pre-mRNA splicing, resulting in an in-frame deletion (p(Ser367_Asn579del)). Family investigation revealed varying degrees of ophthalmologic impairment in the patient's mother and half-sister, both carrying the same mutation.

CONCLUSIONS

This case report provides the first clinical description of the c.1101-1 G>T mutation in the BEST1 gene associated with ADVIRC. The presence of intrafamilial variability, as evidenced by the differing clinical features observed in the index case and her half-sister, suggests the potential involvement of mechanisms influencing phenotype expression.Abbreviation: ADVIRC : autosomal dominant vitreoretinochoroidopathy; RNA : ribonucleic acid; RPE : retinal pigment epithelium.

Variable expressivity of BEST1-associated autosomal dominant vitreoretinochoroidopathy (ADVIRC) in a three-generation pedigree

Objective

Autosomal dominant vitreoretinochoroidopathy (ADVIRC) is associated with pathogenic variants in BEST1, which typically causes visual impairment in the late stage of disease. We present a pedigree with variable expressivity and the youngest case in the literature with visual impairment in early childhood.

Methods and analysis

This is a retrospective, observational, case series describing multigenerational members of one family affected with ADVIRC. Patients underwent examination, ultra-widefield fundus photography and angiography, optical coherence tomography, full-field electroretinography (ffERG) and full-field perimetry.

Results

Three affected members of the pedigree, one from each successive generation, were found to harbour a mutation, c.715G>A:p.Val239Met, in BEST1. The proband characterised in this report is, to our knowledge, the youngest documented case of ADVIRC in early childhood. Yet, this patient has the most severe retinal dysfunction compared with the father and paternal grandmother, whom exhibit classic characteristics of ADVIRC. Longitudinal data from the paternal grandmother showed that there was a rapid decline in ffERG responses (photopic decline worse than scotopic) from the fourth to fifth decade of life, which correlated with severe concentric constriction of visual fields.

Conclusion

This multigenerational case series provides new insights into the ADVIRC disease spectrum and rate of progression. While ADVIRC typically causes a slowly progressive disease, we show that variable phenotypic expressivity is possible among affected members of the same family with the same mutation in BEST1. Thus, ADVIRC must also be considered in the differential diagnosis of paediatric patients with severe retinal dystrophy in early childhood.

A novel missense mutation in BEST1 associated with an autosomal-dominant vitreoretinochoroidopathy (ADVIRC) phenotype

BACKGROUND

To report a 68-year-old female with an autosomal-dominant vitreoretinochoroidopathy (ADVIRC) phenotype associated with a subretinal hemorrhage (SRH) and novel BEST1 pathogenic variation p.Met571Thr.

MATERIALS AND METHODS

The patient was assessed by fundus photography, fluorescence and indocyanine green angiography, spectral-domain optical coherence tomography, photopic and scotopic electroretinogram (ERG), and electrooculogram (EOG). Whole-exome and Sanger sequencing of the patient's and selected family members' DNA was performed. Ophthalmoscopic examinations were also performed on six patient's relatives.

RESULTS

The patient presented moderate vitreous and SRH in the left eye. A distinct, annular hyperpigmented band was present in both eyes. Vitrectomy improved visual acuity, and the SRH gradually regressed without recurrence. Preserved macular function was shown by optical coherence tomography (OCT). Genetic analysis identified a novel heterozygous mutation, resulting in p.Met571Thr in BEST1. No mutations were observed in a panel of other eye disease genes, suggesting that this pathogenic variation in BEST1 is associated with an ADVIRC phenotype. No other evaluated family member had the variant or the fundus findings.

CONCLUSIONS

We present a patient with a novel p.Met571Thr pathogenic variation associated with an ADVIRC phenotype. SRH is a unique finding in ADVIRC patients and may correspond to peripheral exudative hemorrhagic chorioretinopathy. The BEST1 pathogenic variation p.Met571Thr might be the likely cause of ADVIRC in this patient. However, further study is necessary to determine whether this mutation is causative.

Ocular Histopathology and Immunohistochemical Analysis in the Oldest Known Individual with Autosomal Dominant Vitreoretinochoroidopathy

PURPOSE

To assess the immunohistochemical and histopathological changes in a subject with Autosomal Dominant Vitreoretinochoroidopathy (ADVIRC).

DESIGN

Case study.

PARTICIPANT

Ninety two year-old Caucasian male with ADVIRC.

METHODS

The subject was documented clinically for 54 Years. The retina/choroid complex of the right eye was evaluated with cryosections stained with hematoxylin and eosin or periodic acid schiff reagent. Cryosections were also evaluated with immunofluorescence or alkaline phosphatase immunohistochemistry (IHC) using primary antibodies against bestrophin1, GFAP, PEDF, RPE65, TGFβ, VEGF, and vimentin. The left retina and choroid were evaluated as flat mounts using immunofluorescence. UEA lectin was used to stain viable vasculature.

MAIN OUTCOME MEASURES

The immunohistochemical and histopathological changes in retina and choroid from a subject with ADVIRC.

RESULTS

The subject had a heterozygous c.248G>A variant in exon 4 of the BEST1 gene. There was widespread chorioretinal degeneration and atrophy except for an island of spared RPE monolayer in the perimacula/macula OU. In this region, some photoreceptors were present, choriocapillaris was spared, and retinal pigment epithelial cells were in their normal disposition. There was a Muller cell periretinal membrane throughout much of the fundus. Bestrophin-1 was not detected or only minimally present by IHC in the ADVIRC RPE, even in the spared RPE area. Beyond the island of retained RPE monolayer on Bruch's membrane (BrMb), there was migration of RPE into the neuro-retina, often ensheathing blood vessels and producing excessive matrix within their perivascular aggregations.

CONCLUSIONS

The primary defect in ADVIRC is in RPE, the only cells in the eye that express the BEST1 gene. The dysfunctional RPE cells may go through epithelial/mesenchymal transition as they migrate from BrMb to form papillary aggregations in the neuro-retina, often ensheathing blood vessels. This may be the reason for retinal blood vessel nonperfusion. Migration of RPE from BrMb was also associated with attenuation of the choriocapillaris.

AUTOSOMAL DOMINANT VITREORETINOCHOROIDOPATHY: When Molecular Genetic Testing Helps Clinical Diagnosis

PURPOSE

Autosomal dominant vitreoretinochoroidopathy is an extremely rare disease, which belongs to the BEST1-related disease spectrum.

METHODS

Report of five patients with an initial diagnosis of atypical rod-cone dystrophy, for whom autosomal dominant vitreoretinochoroidopathy was retrospectively diagnosed on genetic results using targeted next-generation sequencing. Each patient had a comprehensive ophthalmic examination including multimodal retinal imaging and functional evaluation.

RESULTS

Visual acuity ranged from <20/800 to 20/25. Two patients had narrowed angle with history of acute angle-closure glaucoma for one patient. Full-field electroretinogram showed severe reduction of both scotopic and photopic responses for 3/5 patients. Electrooculogram could be performed for one of the two patients with moderate alterations of full-field electroretinogram. It revealed severe light rise abnormalities with decreased Arden ratio (125% right eye, 145% left eye) in keeping with generalized severe dysfunction of the retinal pigment epithelium. On fundoscopy, the pathognomonic circumferential hyperpigmented band of the peripheral retina was totally absent in two patients.

CONCLUSION

This report highlights the high phenotypic variability of autosomal dominant vitreoretinochoroidopathy, which may be misdiagnosed, especially in advanced forms with severe generalized photoreceptor dysfunction mimicking retinitis pigmentosa. Targeted next-generation sequencing can contribute to the proper clinical diagnosis, especially in case of atypical phenotypic features of autosomal dominant vitreoretinochoroidopathy.

Bestrophin 1 and retinal disease

Mutations in the gene BEST1 are causally associated with as many as five clinically distinct retinal degenerative diseases, which are collectively referred to as the "bestrophinopathies". These five associated diseases are: Best vitelliform macular dystrophy, autosomal recessive bestrophinopathy, adult-onset vitelliform macular dystrophy, autosomal dominant vitreoretinochoroidopathy, and retinitis pigmentosa. The most common of these is Best vitelliform macular dystrophy. Bestrophin 1 (Best1), the protein encoded by the gene BEST1, has been the subject of a great deal of research since it was first identified nearly two decades ago. Today we know that Best1 functions as both a pentameric anion channel and a regulator of intracellular Ca²⁺ signaling. Best1 is an integral membrane protein which, within the eye, is uniquely expressed in the retinal pigment epithelium where it predominantly localizes to the basolateral plasma membrane. Within the brain, Best1 expression has been documented in both glial cells and astrocytes where it functions in both tonic GABA release and glutamate transport. The crystal structure of Best1 has revealed critical information about how Best1 functions as an ion channel and how Ca²⁺ regulates that function. Studies using animal models have led to critical insights into the physiological roles of Best1 and advances in stem cell technology have allowed for the development of patient-derived, "disease in a dish" models. In this article we review our knowledge of Best1 and discuss prospects for near-term clinical trials to test therapies for the bestrophinopathies, a currently incurable and untreatable set of diseases.

Mislocalisation of BEST1 in iPSC-derived retinal pigment epithelial cells from a family with autosomal dominant vitreoretinochoroidopathy (ADVIRC)

Autosomal dominant vitreoretinochoroidopathy (ADVIRC) is a rare, early-onset retinal dystrophy characterised by distinct bands of circumferential pigmentary degeneration in the peripheral retina and developmental eye defects. ADVIRC is caused by mutations in the Bestrophin1 (BEST1) gene, which encodes a transmembrane protein thought to function as an ion channel in the basolateral membrane of retinal pigment epithelial (RPE) cells. Previous studies suggest that the distinct ADVIRC phenotype results from alternative splicing of BEST1 pre-mRNA. Here, we have used induced pluripotent stem cell (iPSC) technology to investigate the effects of an ADVIRC associated BEST1 mutation (c.704T > C, p.V235A) in patient-derived iPSC-RPE. We found no evidence of alternate splicing of the BEST1 transcript in ADVIRC iPSC-RPE, however in patient-derived iPSC-RPE, BEST1 was expressed at the basolateral membrane and the apical membrane. During human eye development we show that BEST1 is expressed more abundantly in peripheral RPE compared to central RPE and is also expressed in cells of the developing retina. These results suggest that higher levels of mislocalised BEST1 expression in the periphery, from an early developmental stage, could provide a mechanism that leads to the distinct clinical phenotype observed in ADVIRC patients.

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.

Fundus Autofluorescence and SD-OCT Document Rapid Progression in Autosomal Dominant Vitreoretinochoroidopathy (ADVIRC) Associated with a c.256G > A Mutation in BEST1

PURPOSE

To report the variability of clinical findings, rapid concentric progression, and successful treatment of macular edema in autosomal dominant vitreoretinochoroidopathy (ADVIRC) associated with a heterozygous c.256G > A missense mutation in the bestrophin-1 (BEST1) gene.

METHODS

Three affected members of a four-generation ADVIRC family were examined with fundus autofluorescence (FAF), near-infrared autofluorescence (NIA) and spectral domain optical coherence tomography (SD-OCT). Direct sequence analysis of coding and flanking intronic regions of the BEST1 gene was performed.

RESULTS

Disease manifestations presented with high variability with visual problems manifesting between 10 and 40 years of age. Two probands showed marked signs of peripheral degeneration, while this retinal area was not noticeably affected in the third. Cystoid macular edema was present in one proband, which responded to long-term treatment with topic dorzolamide with improved visual acuity. FAF and NIA revealed mid-peripheral retinal degeneration in areas that appeared normal on ophthalmoscopy. The full-field ERG was markedly reduced in two probands. Within a 5-year period a marked increase in concentric progression of degeneration including the posterior pole was documented with FAF, NIA and SD-OCT in one proband after the age of 63 years. Direct sequence analysis of the BEST1 gene revealed a heterozygous c.256G > A missense mutation in the three affected probands.

CONCLUSION

The findings in this family emphasize the previously noted variability of clinical manifestations in BEST1-associated ADVIRC and the relevance of FAF and NIA imaging. Cystoid macular edema and vascular leakage can be successfully treated using dorzolamide.

Progressive Cone Dysfunction and Geographic Atrophy of the Macula in Late Stage Autosomal Dominant Vitreoretinochoroidopathy (ADVIRC)

Autosomal dominant vitreoretinochoroidopathy (ADVIRC) is a rare inherited ocular disease associated with distinct mutations in the BEST1 gene. Typically, patients have only mild visual impairment, and rarely do patients have moderate or severe visual impairment, often as a result of vitreous hemorrhage. We now describe progressive central macular atrophy and cone dysfunction leading to visual loss in an elderly ADVIRC patient 33 years after initial presentation.

The light peak of the electroretinogram is dependent on voltage-gated calcium channels and antagonized by bestrophin (best-1)

Mutations in VMD2, encoding bestrophin (best-1), cause Best vitelliform macular dystrophy (BMD), adult-onset vitelliform macular dystrophy (AVMD), and autosomal dominant vitreoretinochoroidopathy (ADVIRC). BMD is distinguished from AVMD by a diminished electrooculogram light peak (LP) in the absence of changes in the flash electroretinogram. Although the LP is thought to be generated by best-1, we find enhanced LP luminance responsiveness with normal amplitude in Vmd2-/- mice and no differences in cellular Cl- currents in comparison to Vmd2+/+ littermates. The putative Ca2+ sensitivity of best-1, and our recent observation that best-1 alters the kinetics of voltage-dependent Ca2+ channels (VDCC), led us to examine the role of VDCCs in the LP. Nimodipine diminished the LP, leading us to survey VDCC beta-subunit mutant mice. Lethargic mice, which harbor a loss of function mutation in the beta4 subunit of VDCCs, exhibited a significant shift in LP luminance response, establishing a role for Ca2+ in LP generation. When stimulated with ATP, which increases [Ca++]I, retinal pigment epithelial cells derived from Vmd2-/- mice exhibited a fivefold greater response than Vmd2+/+ littermates, indicating that best-1 can suppress the rise in [Ca2+]I associated with the LP. We conclude that VDCCs regulated by a beta4 subunit are required to generate the LP and that best-1 antagonizes the LP luminance response potentially via its ability to modulate VDCC function. Furthermore, we suggest that the loss of vision associated with BMD is not caused by the same pathologic process as the diminished LP, but rather is caused by as yet unidentified effects of best-1 on other cellular processes.

Peripheral proliferative retinopathies: an update on angiogenesis, etiologies and management

Many clinical entities may be associated with the development of peripheral retinal neovascularization. In this paper, we review the mechanisms of normal and abnormal angiogenesis in the retina. Specific disease entities associated with peripheral proliferative retinopathies are discussed. These include vascular disease with ischemia, inflammatory diseases with possible ischemia and a variety of miscellaneous causes, including hereditary diseases and tumors. Basic principles for the clinical evaluation of patients with retinal neovascularization are described. Finally, the treatments for retinal neovascularization, including cryopexy and local and panretinal photocoagulation are reviewed, and techniques and possible mechanisms of the beneficial results of treatment are described.

Autosomal dominant neovascular inflammatory vitreoretinopathy

Twenty-eight of 61 members of a six-generation family are affected by an autosomal dominant eye disease which has not been described previously. Affected patients are asymptomatic in early adulthood, but have vitreous cells and the selective loss of the b-wave on the electroretinogram. Later, peripheral retinal scarring and pigmentation, peripheral arteriolar closure, and neovascularization of the peripheral retina at the ora serrata or occasionally neovascularization of the optic disc develop. Cystoid macular edema, vitreous hemorrhage, tractional retinal detachment, and neovascular glaucoma can cause profound visual loss. Vitrectomy reduces traction on the retina and allows for retinal reattachment. The role of argon laser photocoagulation or cryopexy in reducing the neovascular complications remains uncertain.

Histopathologic study of autosomal dominant vitreoretinochoroidopathy. Peripheral annular pigmentary dystrophy of the retina

Autosomal dominant vitreoretinochoroidopathy (ADVIRC), a recently described disease, is clinically characterized by a slowly progressive or stationary circumferential peripheral pigmentary retinopathy with fibrillar condensation of the vitreous. Histopathologic study of an 88-year-old patient with this disease showed disorganization of the peripheral retina with focally atrophic retinal pigment epithelium (RPE). Altered pigment epithelial cells surrounded retinal blood vessels and lined the internal limiting membrane. At the equator, a remarkable and possibly unique multifocal loss of photoreceptor cells was seen. An extensive preretinal membrane, consisting of condensed vitreous with cellular debris and layers of Müller cells, was demonstrated by electron microscopic examination and immunohistochemistry. Histologically, this entity has some similarities to and some differences from retinitis pigmentosa. The clinical features are distinctive.