BEST1 Variant Associated with an Atypical Macular and Peripheral Retinal Phenotype.

PURPOSE: Best vitelliform macular dystrophy (BVMD) is an inherited macular dystrophy associated with over 250 pathogenic variants of the Bestrophin-1 (BEST1) gene. While several of the types of lesions of BVMD are well-described, reports of phenotypic variations associated with rare genetic variants are limited. METHODS: Retrospective case-series performed in 2021 at a tertiary eye care center. PATIENTS: Three members of one family referred to a tertiary eye care clinic for evaluation of their autosomal dominant macular dystrophy. RESULTS: Study subjects presented with atypical findings of peripheral schisis-like lesions and atrophy with abnormal electroretinogram (ERG) in addition to typical macular lesions found in BVMD. Genetic analyses identified a heterozygous BEST1 c.227T>A, p.(Ile76Asn) pathogenic variant in all three subjects. CONCLUSIONS: This study represents the first report of the phenotype associated with the c.227T>A, p.(Ile76Asn) BEST1 variant, which - while mentioned twice in the literature - has not been previously described. The phenotype is unique, comprising features of typical BVMD with ERG and peripheral findings, suggestive of a panretinal dysfunction.

A novel ocular phenotype associated with pathogenic variants in MFSD8 leading to macular dystrophy.

BACKGROUND: The major facilitator superfamily domain-containing protein 8 (MFSD8) pathogenic variants are classically associated with autosomal recessive neuronal ceroid lipofuscinosis-7. Case reports have recently demonstrated an association of MFSD8 variants causing autosomal recessive macular dystrophy with central cone involvement without neurologic sequelae. We report a patient with a novel ocular phenotype associated with MFSD8 pathogenic variants causing macular dystrophy without systemic findings. CASE PRESENTATION: A 37-year-old female presented with a 20-year history of progressive bilateral vision loss. Fundus examination was notable for a slight pigmentary ring around the fovea in both eyes. Optical coherence tomography (OCT) of the macula showed bilateral subfoveal ellipsoid zone loss without outer retinal changes. Fundus autofluorescence (FAF) demonstrated foveal hypo-autofluorescence (AF) in both eyes as well as hyper-AF nasally to the optic nerve in the perifoveal area. Full-field and multifocal electroretinography demonstrated cone dysfunction with diffuse macular changes in both eyes. Subsequent genetic testing identified two pathogenic MFSD8 variants. The patient had no neurologic symptoms consistent with variant-late infantile neuronal ceroid lipofuscinosis. CONCLUSION: MFSD8 pathogenic variants are known to cause macular dystrophies. We report a novel MFSD8-associated macular dystrophy phenotype demonstrating foveal-limited disease with cavitary changes on OCT without inner retinal atrophy and foveal-specific changes on FAF. A threshold model can explain how a hypomorphic missense variant heterozygous with a loss-of-function nonsense variant can lead to a predominantly ocular phenotype with preserved neurologic function. We recommend careful monitoring of these patients for future signs of both retinal and systemic disease progression.

TOPICAL CARBONIC ANHYDRASE INHIBITORS IN THE LONG-TERM TREATMENT OF JUVENILE X-LINKED RETINOSCHISIS.

PURPOSE: To describe the response to long-term topical dorzolamide treatment in patients with juvenile X-linked retinoschisis and cystic-like foveal lesions. METHODS: This was a retrospective interventional case series that included 18 eyes of 10 patients with genetically confirmed juvenile X-linked retinoschisis examined at the Cleveland Clinic Cole Eye Institute, a tertiary referral center, between 2005 and 2021. Patients were treated with topical 2% dorzolamide two to three times daily in both eyes. Two eyes were excluded because of retinal detachment. Primary outcome measures were logarithm of minimum angle of resolution visual acuity and optical coherence tomography based central subfield thickness. RESULTS: The mean follow-up was 8.38 years (SD, 3.41 years). The mean baseline and final central subfield thickness was 429.88 µ m (SD, 143.36 µ m) and 372.28 µ m, respectively (SD, 147.13 µ m, P = 0.10). The mean baseline and final logarithm of minimum angle of resolution visual acuity was 0.45 (SD, 0.17) and 0.34, respectively (SD, 0.22, P < 0.01). None of the patients experienced any side effects from topical dorzolamide. CONCLUSION: The study data support previous reports of improved visual acuity in X-linked retinoschisis patients on topical dorzolamide treatment. This is the longest follow-up for a series of juvenile X-linked retinoschisis patients treated with a topical carbonic anhydrase inhibitor to date. A large, prospective, randomized clinical trial is needed to provide stronger evidence regarding the efficacy of topical carbonic anhydrase inhibitors in juvenile X-linked retinoschisis.

Correlation between Argus II array-retina distance and electrical thresholds of stimulation is improved by measuring the entire array.

PURPOSE: To describe two methods of measuring Argus II array-retina distance and to correlate array-retina distance to electrode stimulation thresholds. METHODS: This was a case series of eight patients implanted with the Argus II. Spectral domain-optical coherence tomography array-retina distance was measured by two methods and correlated to corresponding electrode thresholds: (1) array-retina distance at each array corner and the largest array-retina distance and (2) using manual optical coherence tomography segmentation, the average array-retina distance was determined for each group of four electrodes. Patients 1-5 and 6-8 were analyzed separately due to a different threshold programming software. RESULTS: The Spearman's rank coefficient between array-retina distance and thresholds was -0.006 (p = 0.98) for patients 1-5, and 0.16 (p = 0.59) for patients 6-8 with the first method. The Spearman's rank coefficient was 0.25 (p < 0.001) for patients 1-5 and 0.36 (p < 0.001) for patients 6-8 with the second method. CONCLUSION: There is a positive correlation between array-retina distance and threshold measurements when measuring the entire array but not when using a faster measurement method of four corners and largest array-retina distance.

Cellular Changes in Retinas From Patients With BEST1 Mutations.

Best disease (BD), also known as vitelliform macular dystrophy, is an inherited disease of the central retina caused by more than 300 pathogenic variants in the BEST1 gene. The phenotype of BD is variable, and there are just a few reports on the histopathology of eyes from donors with BD. Here, we describe the histopathological comparison of donor's eyes from two patients with BD. Eyes obtained from 85-year-old (donor 1) and 65-year-old (donor 2) donors were fixed within 25 h postmortem. Perifoveal and peripheral retinal regions were processed for histology and immunocytochemistry using retinal-specific and retinal pigment epithelium (RPE)-specific antibodies. Three age-matched normal eyes were used as controls. DNA was obtained from donor blood samples. Sequence analysis of the entire BEST1 coding region was performed and identified a c.886A > C (p.Asn296His) variant in donor 1 and a c.602T > C (p.Ile201Thr) variant in donor 2; both mutations were heterozygous. Fundus examination showed that donor 1 displayed a macular lesion with considerable scarring while donor 2 displayed close to normal macular morphology. Our studies of histology and molecular pathology in the perifovea and periphery of these two BD donor eyes revealed panretinal abnormalities in both photoreceptors and RPE cellular levels in the periphery; donor 1 also displayed macular lesion. Our findings confirm the phenotypic variability of BD associated with BEST1 variants.

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.

An Online Application for Retinoblastoma Surveillance.

BACKGROUND: Retinoblastoma (RB) is a potentially heritable childhood cancer that is vision- and life-threatening. Assessing the risk of inheriting RB is important for structuring ophthalmic and genetic screening of family members. PURPOSE: To create a free online application that integrates phenotypic, genetic, and familial relationships with clinical best practice surveillance guidelines for families with RB. METHODS: The risk of germline RB1 gene mutation was assessed for first- and second-degree relatives of a proband under variable clinical scenarios, integrating age, phenotype, relationship data, and genotype (germline RB1 mutation status: detected, undetected, not tested). Based on the assessed risk of a germline RB1 mutation, recommendations regarding further genetic testing as well as ophthalmic surveillance were derived from consensus guidelines. RESULTS: The recommendations depend on the RB1 germline mutation status (detected, undetected, not tested), which were further subcategorized by the results of tumor phenotype, relationship to proband, age of the relative, and family structure. The online application is available at https://nakul-singh.shinyapps.io/RB_Screening_rec/. CONCLUSIONS: The assessed risk of germline RB1 mutation determines ophthalmic surveillance recommendations. The tool may have most value in regions where access to specialized care is limited.

A novel TIMP3 mutation associated with a retinitis pigmentosa-like phenotype.

BACKGROUND: Sorsby Fundus Dystrophy is an inherited macular degeneration caused by pathogenic variants in the TIMP3 gene. Clinical exam findings typically drusen -like deposits beneath the RPE or reticular pseudo drusen deposits above the RPE with a majority of patients developing choroidal neovascularization. MATERIALS AND METHODS: Case report of two members of a family that present with atypical clinical exam findings. Protein modeling of the novel Y137CTIMP3 variant was performed and compared with other known variants. RESULTS: In this study we describe a father and son initially diagnosed with retinitis pigmentosa of unknown genetic origin. More recent genetic testing of the patients, identified a novel c.410A>G; p.Tyr137Cys variant of uncertain clinical significance in the Tissue Inhibitor of Metalloproteinase-3 (TIMP3) gene. The atypical clinical findings led us to compare the theoretical molecular effects of this variant on the TIMP3 protein structure and interactions with other proteins using homology modeling and machine learning predictions. CONCLUSIONS: It is important to consider mutations in TIMP3 in atypical cases of Retinitis Pigmentosa particularly in the absence of known variants.

Hickam's Dictum: Pseudoxanthoma elasticum and Usher syndrome in a single patient.

BACKGROUND: To report the case of a patient with two distinct genetic systemic diseases - pseudoxanthoma elasticum (PXE) and Usher syndrome - confirmed by genetic testing. MATERIALS AND METHODS: Single Retrospective Case Report. RESULTS: A 36-year-old woman presented with acute central vision loss of the left eye (OS). Fundus exam revealed choroidal neovascularization OS in the setting of angioid streaks secondary to an underlying diagnosis of PXE. Unexpectedly, she also exhibited peripheral bony spicules with significant visual field constriction. Physical exam revealed skin papules on her neck and hearing loss. The presence of angioid streaks and skin findings was compatible with PXE; the etiology of her pigmentary retinopathy and hearing loss was elucidated using genetic testing. The patient was found to be compound heterozygous for pathogenic variants in both the ABCC6 and USH2A genes, confirming the diagnosis of two rare disorders in a single patient. CONCLUSIONS: PXE and Usher syndrome are rare systemic disorders that cause distinctive retinal abnormalities. This report highlights the importance of genetic testing in diagnosing uncommon hereditary retinal disorders and outlines the progression of disease over 6 years.

Whole Exome Sequencing Identifies Candidate Genes Associated with Hereditary Predisposition to Uveal Melanoma.

PURPOSE: To identify susceptibility genes associated with hereditary predisposition to uveal melanoma (UM) in patients with no detectable germline BAP1 alterations. DESIGN: Retrospective case series from academic referral centers. PARTICIPANTS: Cohort of 154 UM patients with high risk of hereditary cancer defined as patients with 1 or more of the following: (1) familial UM, (2) young age (<35 years) at diagnosis, (3) personal history of other primary cancers, and (4) family history of 2 or more primary cancers with no detectable mutation or deletion in BAP1 gene. METHODS: Whole exome sequencing, a cancer gene panel, or both were carried out. Probands included 27 patients with familial UM, 1 patient with bilateral UM, 1 patient with congenital UM, and 125 UM patients with strong personal or family histories, or both, of cancer. Functional validation of variants was carried out by immunohistochemistry, reverse-transcriptase polymerase chain reaction, and genotyping. MAIN OUTCOME MEASURES: Clinical characterization of UM patients with germline alterations in known cancer genes. RESULTS: We identified actionable pathogenic variants in 8 known hereditary cancer predisposition genes (PALB2, MLH1, MSH6, CHEK2, SMARCE1, ATM, BRCA1, and CTNNA1) in 9 patients, including 3 of 27 patients (11%) with familial UM and 6 of 127 patients (4.7%) with a high risk for cancer. Two patients showed pathogenic variants in CHEK2 and PALB2, whereas variants in the other genes each occurred in 1 patient. Biallelic inactivation of PALB2 and MLH1 was observed in tumors from the respective patients. The frequencies of pathogenic variants in PALB2, MLH1, and SMARCE1 in UM patients were significantly higher than the observed frequencies in noncancer controls (PALB2: P = 0.02; odds ratio, 8.9; 95% confidence interval, 1.5-30.6; MLH1: P = 0.04; odds ratio, 25.4; 95% confidence interval, 1.2-143; SMARCE1: P = 0.001; odds ratio, 2047; 95% confidence interval, 52-4.5e15, respectively). CONCLUSIONS: The study provided moderate evidence of gene and disease association of germline mutations in PALB2 and MLH1 with hereditary predisposition to UM. It also identified several other candidate susceptibility genes. The results suggest locus heterogeneity in predisposition to UM. Genetic testing for hereditary predisposition to cancer is warranted in UM patients with strong personal or family history of cancers, or both.

Novel mutation in CTNNB1 causes familial exudative vitreoretinopathy (FEVR) and microcephaly: case report and review of the literature.

Purpose: Neonatal retinal folds and/or vitreoretinal traction can be signs of isolated ocular or syndromic disorders. Etiologies include retinopathy of prematurity, perinatal infections or inherited vitreoretinal disorders such as familial exudative vitreoretinopathy (FEVR) or Norrie disease. We present the clinical and genetic findings of a two-month-old infant with microcephaly, mild motor developmental delay, and FEVR, who required urgent surgical interventions.Methods: The patient underwent an initial examination under anesthesia (EUA) with fluorescein angiography (FA) and subsequent medical and surgical treatments. Genetic testing was undertaken to identify the etiology.Results: Examination at 2 months of age demonstrated microcephaly with a head circumference smaller than the 1st percentile. Family history was negative for microcephaly or retinal disease. Anterior segment eye exam was normal OU. There were bilateral macular folds involving the fovea and extending from the disc to the temporal periphery. FA demonstrated bilateral incomplete vascularization of the retina most notable nasally. Indirect laser was applied to ischemic retina OU. Scleral buckling procedures were performed OU as well as a vitrectomy in the left eye. Follow-up examinations demonstrated the stable appearance of the folds and attached retinas OU. Genetic testing identified a novel dominant heterozygous c.2046_2047del [p.Phe683Glnfs*9] mutation in CTNNB1, predicted to result in a frameshift causing a truncated protein.Conclusions: CTNNB1 mutations are an uncommon cause of FEVR with microcephaly.

Retinal dystrophy associated with a Kizuna (KIZ) mutation and a predominantly macular phenotype.

Introduction: Mutations in Kizuna (KIZ), a gene involved in ciliary function, have been previously associated with rod-cone dystrophy with relative macular sparing and a number of other systemic abnormalities.Purpose: We present a patient with a phenotype dominated by retinal dystrophy and macular cysts as a result of a homozygous nonsense mutation in KIZ.Methods: A 32-year-old female of Ashkenazi Jewish ancestry presented with progressive central vision loss and peripheral visual field loss following decades of night-blindness. She was noted to have a bull's-eye pattern of macular hyper-autofluorescence, intraretinal cystoid macular changes and outer retinal atrophy in both eyes. Visual fields were constricted to <10 degrees centrally with inferior preserved islands of vision. Genetic testing revealed a homozygous KIZ c.226 C > T (p.Arg76*) nonsense mutation. The patient was treated with topical dorzolamide and showed significant improvement in the degree of macular cysts.Conclusion: Mutations in KIZ can present with a predominantly macular phenotype and develop cystoid macular changes responsive to carbonic anhydrase inhibitor treatment. Because of the importance of KIZ in cilia function, it is critical to look for associated systemic manifestations to ensure best patient care.

A novel dominant CRX mutation causes adult-onset macular dystrophy.

BACKGROUND: To present the ophthalmological findings of a mother and son initially diagnosed with benign concentric annular macular dystrophy (BCAMD) and later discovered to carry a novel nonsense mutation in the cone-rod homeobox (CRX) gene (19q13.3). MATERIALS AND METHODS: Patients received ophthalmic examinations and diagnostic testing. The proband underwent sequencing of 131 retinal dystrophy genes. His mother had targeted testing of the identified sequence variations in CRX and BBS12 (4q27). RESULTS: The proband (Case I) presented at age 35 years for routine care. He had several male and female relatives with adult-onset retinal degeneration. Over 11 years, visual acuity (VA) dropped from 20/20 OU to 20/25 OD and 20/50 OS. Ophthalmoscopy showed bull's eye macular lesions OU. The proband's mother (Case II) presented at age 57 years with unilateral, progressive vision loss. Over 5 years, VA fluctuated 20/80-20/400 OD and remained 20/25 OS. Ophthalmoscopy showed similar findings to Case I. A clinical diagnosis of BCAMD was given because of the characteristic retinal lesion, preserved VA, and presumed autosomal dominant inheritance. Genetic testing identified a novel nonsense mutation in CRX (c.766C>T; p.Gln256Ter) in both patients. The son was also heterozygous for a missense mutation in BBS12 (c.1859A>G; p.Gln620Arg), which was absent in Case II. CONCLUSIONS: CRX mutations are associated with a variety of clinical phenotypes, including an adult-onset macular dystrophy that simulates BCAMD with a bull's eye macular lesion and fairly well preserved VA.