Sector retinitis pigmentosa

Genotypes and clinical features of RHO-associated retinitis pigmentosa in a Japanese population

PURPOSE

To report the genotypes and clinical features of RHO-associated retinitis pigmentosa (RHO-RP) in the Kyushu region of Japan.

STUDY DESIGN

Retrospective, single-center study.

METHODS

Sixteen RP patients with pathogenic RHO variants seen at Kyushu University Hospital were investigated. Clinical data including age, best-corrected visual acuity (BCVA) in logarithm of the minimum angle of resolution (logMAR) units, visual field, fundus photography, and optical coherence tomography were retrospectively obtained. Visual outcomes were compared between classical and sector phenotypes and among genetic variants.

RESULTS

The mean age at the first visit was 54.0 ± 15.7 years, with a mean follow-up of 7.6 ± 4.0 years. Fourteen patients (87.5%) showed the classical RP phenotype, of whom four were associated with p.[Pro23Leu] and two had p.[Pro347Leu] variants. In addition, two patients with the sector phenotype harbored p.[Ala164Val] variants. Among the classical RHO-RP patients, the mean BCVA decreased from 0.60 to 1.08 logMAR over the follow-up period (7.4 ± 4.1 years) whereas BCVA was preserved at 0.04 logMAR in sector RHO-RP patients (9.0 ± 3.0 years). Genotype-to-phenotype analysis demonstrated that p.[Pro347Leu] was associated with severe vision loss at an earlier age. Macular complications such as epiretinal membrane and cystoid macular edema were observed in 5 classical RHO-RP patients.

CONCLUSION

p.[Pro23Leu], but not p.[Pro23His], was a frequent variant causing RHO-RP in the Kyushu region of Japan. As reported in previous studies, patients with the p.[Pro347Leu] variant showed a more severe phenotype, and variants causing sector RHO-RP were associated with a good prognosis.

Clinical and genetic features of Koreans with retinitis pigmentosa associated with mutations in rhodopsin

Purpose: To investigate the clinical features, natural course, and genetic characteristics of Koreans with rhodopsin-associated retinitis pigmentosa (RHO-associated RP). Design: We conducted a retrospective, multicenter, observational cohort study. Participants: We reviewed the medical records of 42 patients with RHO-associated RP of 36 families who visited 4 hospitals in Korea. Methods: Patients with molecular confirmation of pathogenic variants of the RHO gene were included. The patients were divided into two subgroups: the generalized and sector RP groups. A central visual field of the better-seeing eye of <10° or a best-corrected visual acuity of the better-seeing eye <20/40 indicated the progression to late-stage RP. Results: The mean age at which symptoms first appeared was 26.3 ± 17.9 years (range: 8-78 years), and the mean follow-up period was 80.9 ± 68.7 months (range: 6-268 months). At the last follow-up visit, the generalized RP group showed a significantly higher rate of visual field impairment progression to late-stage RP than that of the sector RP group (22 of 35 [62.9%] vs. 0 of 7 [0.0%], p = 0.003). No cases in the sector RP group progressed to generalized RP. Best-corrected visual acuity deterioration to late-stage RP was observed only in the generalized RP group (13 of 35 patients; 37.1%), whereas no deterioration was observed in the sector RP group. We identified 16 known and three novel RHO mutations, including two missense mutations (p.T108P and p.G121R) and one deletion mutation (p.P347_A348del). The pathogenic variants were most frequently detected in exon 1 (14 of 36 [38.9%]). The most common pathogenic variants were p.P347L and T17M (5 of 36 [13.9%] families). Among 42 patients of 36 families, 35 patients of 29 families (80.6%) presented with the generalized RP phenotype, and seven patients of seven families (19.4%) presented with the sector RP phenotype. Three variants (p.T17M, p.G101E, and p.E181K) presented with both the generalized and sector RP phenotypes. Conclusion: This multicenter cohort study provided information on the clinical and genetic features of RHO-associated RP in Koreans. It is clinically important to expand the genetic spectrum and understand genotype-phenotype correlations to ultimately facilitate the development of gene therapy.

Multimodal image alignment aids in the evaluation and monitoring of sector retinitis pigmentosa

PURPOSE

To present a semi-automated method of image alignment to aid in monitoring the progression of inherited retinal degenerations (IRDs).

RESULTS

A 22-year-old woman presented with nyctalopia and a family history of retinitis pigmentosa (RP), but with no prior genetic testing. Fundus examination showed a sectoral retinal degeneration involving the inferior and nasal retina with rare, pigmented deposits. Goldmann kinetic perimetry demonstrated corresponding superotemporal visual field defects. The best-corrected visual acuity was 20/20 in both eyes. Multimodal imaging delineated geographically restricted peripheral retinal degeneration extending to the inferior edge of the macula. Central visual function remained intact with normal multifocal electroretinography findings. Optical coherence tomography (OCT) through the leading edge of the retinal degeneration confirmed loss of the photoreceptor layer and associated retinal pigment epithelium. In the region of retinal degeneration, loss of vascular flow density was noted on optical coherence tomography angiography (OCTA). Genetic testing identified a pathologic sequence variant in RHO (c.68C>A, p.Pro23His), confirming autosomal dominant sector retinitis pigmentosa (SRP). Image alignment allowed for precise measurement of the progression of SRP over a period of 18 months.

CONCLUSION

SRP is a rare subtype of RP characterized by focal, typically inferior and nasal, retinal degeneration of the peripheral retina. Although the onset and extent of peripheral retinal degeneration varies, compared with RP, SRP typically progresses more slowly to involve the macula. In this report, we highlight the utility of image registration and alignment to aid in monitoring disease progression in IRDs by means of multimodal imaging.

EYS-Associated Sector Retinitis Pigmentosa

PURPOSE

Sector retinitis pigmentosa (RP) is a rare form of rod-cone degeneration typically associated with mutations in the RHO gene. We describe six unrelated patients presenting with this atypical phenotype in association with biallelic mutations in EYS gene.

METHODS

Multinational, multicentre cross-sectional case series. Patients with biallelic disease-causing variants in EYS and a clinical diagnosis of sector RP were recruited from specialized centres in Portugal and Brazil. All patients underwent a comprehensive ophthalmologic examination complemented by deep phenotyping. Peripheral blood samples were collected from all probands and available relatives for genetic analysis. Genetic counselling was provided to all subjects.

RESULTS

Seven disease-causing variants (4 pathogenic; 3 likely pathogenic) were identified in 6 unrelated female patients. Best-corrected visual acuity ranged from 75 to 85 ETDRS letters. All eyes showed bilateral and symmetrical areas of outer retinal atrophy distributed along the inferior vascular arcades and extending temporally and/or nasally in a crescent-shaped pattern. On fundus autofluorescence (AF), a foveal-sparing curvilinear band of hyperAF encroaching the optic nerve head and extending temporally was seen in 4 patients. The remaining 2 presented bilateral and symmetrical patches of hypoAF inside crescent-shaped areas of hyperAF along the inferior temporal vascular arcade. Visual field testing revealed superior visual field defects of varying extents, always in close association with the fundus AF findings.

CONCLUSIONS

Even though EYS has only recently been listed as a cause of the sector RP phenotype, we believe that this presentation is not infrequent and should be considered an important differential for sector RP.

Polyphenols and Visual Health: Potential Effects on Degenerative Retinal Diseases

Dietary polyphenols are a group of natural compounds that have been proposed to have beneficial effects on human health. They were first known for their antioxidant properties, but several studies over the years have shown that these compounds can exert protective effects against chronic diseases. Nonetheless, the mechanisms underlying these potential benefits are still uncertain and contradictory effects have been reported. In this review, we analyze the potential effects of polyphenol compounds on some visual diseases, with a special focus on retinal degenerative diseases. Current effective therapies for the treatment of such retinal diseases are lacking and new strategies need to be developed. For this reason, there is currently a renewed interest in finding novel ligands (or known ligands with previously unexpected features) that could bind to retinal photoreceptors and modulate their molecular properties. Some polyphenols, especially flavonoids (e.g., quercetin and tannic acid), could attenuate light-induced receptor damage and promote visual health benefits. Recent evidence suggests that certain flavonoids could help stabilize the correctly folded conformation of the visual photoreceptor protein rhodopsin and offset the deleterious effect of retinitis pigmentosa mutations. In this regard, certain polyphenols, like the flavonoids mentioned before, have been shown to improve the stability, expression, regeneration and folding of rhodopsin mutants in experimental in vitro studies. Moreover, these compounds appear to improve the integration of the receptor into the cell membrane while acting against oxidative stress at the same time. We anticipate that polyphenol compounds can be used to target visual photoreceptor proteins, such as rhodopsin, in a way that has only been recently proposed and that these can be used in novel approaches for the treatment of retinal degenerative diseases like retinitis pigmentosa; however, studies in this field are limited and further research is needed in order to properly characterize the effects of these compounds on retinal degenerative diseases through the proposed mechanisms.

Glaucoma Mimickers: A major review of causes, diagnostic evaluation, and recommendations

Background: Glaucoma is characterized by chronic progressive optic neuropathy with corresponding visual field changes, with or without raised intraocular pressure (IOP). When diagnosing glaucoma or monitoring its progression, the examiner has to rely on the appearance of the optic disc, characteristic retinal nerve fiber layer defects, and corresponding visual field defects. However, similar changes and symptoms may be observed in several other disorders of the optic nerve and retina that may mimic glaucoma, often leading to misdiagnosis. Methods and result: The consequences of misdiagnosis not only result in improper treatment that may impact vision but also would negatively affect the overall health, psychological well-being of the patient, and may have considerable economic implications.Conclusion: The current review describes various conditions that mimic glaucoma and the features that help differentiate these conditions from glaucoma.

Multifocal electroretinographic responses in sector retinitis pigmentosa

HEADINGS

Multifocal electroretinography (mfERG) may be useful in the management of sector retinitis pigmentosa (SRP).

AIM

To compare multifocal electroretinographic responses in SRP, generalised retinitis pigmentosa (GRP), and healthy controls.

METHODS

Eighteen patients with SRP, twelve with GRP, and fifteen controls were included in the study. All participants underwent: complete ophthalmological examination, Humphrey visual field testing, full-field ERG, and mfERG. The mean P1 amplitude, the implicit time (IT), and the mapping of the local responses were evaluated.

RESULTS

The mean P1 amplitude was higher in the SRPs than in GRPs (p < 0.001), while it did not differ between SRPs and controls (p = 0.913). In the SRPs, the P1 amplitude in pathologic areas was higher than in the GRPs (p < 0.001). In normal areas, this parameter did not differ from the controls (p = 0.499). Moreover, in the SRPs, no differences in the P1 amplitude and the IT between pigmented and non-pigmented areas were found.

CONCLUSION

In the present study, the mfERG examination displayed significant differences between sector and generalised RP, showing normal values in sector RP even in pigmented areas. Considering the patients included in this study, SRP seems to represent a favourable variant of the disease, characterised by a limited retinal involvement and apparently mild functional damage. It is still unclear how these results can be extended to other forms of SRP.

Sector Retinitis Pigmentosa caused by mutations of the RHO gene

BACKGROUND

Sector retinitis pigmentosa (RP) is an atypical form of RP in which only one or two quadrants of the retina are involved. The objectives of this study were to report the results of a molecular screening of five unrelated Chinese patients with sector RP and describe the clinical features observed in patients with RHO mutations.

METHODS

Five probands that were clinically diagnosed with sector RP were recruited for genetic analysis. They underwent ophthalmic examinations, including best corrected visual acuity, fundus examination, visual field examinations, and electroretinography. A combination of molecular screening methods, including the targeted next-generation sequencing (TES) and sanger-DNA sequencing of RHO, were used to detect mutations. In silico programs were used to analyze the pathogenicity of all the variants.

RESULTS

Three RHO missense mutations (p.T17M, p.L31Q, and p.G106R) were identified in the five unrelated probands. The novel mutation p.L31Q was detected in three unrelated probands. All patients showed bilateral and symmetrical retinal degeneration in the inferior retina and had relatively good visual acuity. Patients with the p.L31Q mutation showed phenotypic variability and variable penetrance.

CONCLUSION

Our results indicate that RHO mutations are also common in Chinese patients with sector RP. The RHO gene should be given priority during mutation screening analysis for Chinese patients with sector RP.

Non-syndromic retinitis pigmentosa

Retinitis pigmentosa (RP) encompasses a group of inherited retinal dystrophies characterized by the primary degeneration of rod and cone photoreceptors. RP is a leading cause of visual disability, with a worldwide prevalence of 1:4000. Although the majority of RP cases are non-syndromic, 20-30% of patients with RP also have an associated non-ocular condition. RP typically manifests with night blindness in adolescence, followed by concentric visual field loss, reflecting the principal dysfunction of rod photoreceptors; central vision loss occurs later in life due to cone dysfunction. Photoreceptor function measured with an electroretinogram is markedly reduced or even absent. Optical coherence tomography (OCT) and fundus autofluorescence (FAF) imaging show a progressive loss of outer retinal layers and altered lipofuscin distribution in a characteristic pattern. Over the past three decades, a vast number of disease-causing variants in more than 80 genes have been associated with non-syndromic RP. The wide heterogeneity of RP makes it challenging to describe the clinical findings and pathogenesis. In this review, we provide a comprehensive overview of the clinical characteristics of RP specific to genetically defined patient subsets. We supply a unique atlas with color fundus photographs of most RP subtypes, and we discuss the relevant considerations with respect to differential diagnoses. In addition, we discuss the genes involved in the pathogenesis of RP, as well as the retinal processes that are affected by pathogenic mutations in these genes. Finally, we review management strategies for patients with RP, including counseling, visual rehabilitation, and current and emerging therapeutic options.

The molecular and cellular basis of rhodopsin retinitis pigmentosa reveals potential strategies for therapy

Inherited mutations in the rod visual pigment, rhodopsin, cause the degenerative blinding condition, retinitis pigmentosa (RP). Over 150 different mutations in rhodopsin have been identified and, collectively, they are the most common cause of autosomal dominant RP (adRP). Mutations in rhodopsin are also associated with dominant congenital stationary night blindness (adCSNB) and, less frequently, recessive RP (arRP). Recessive RP is usually associated with loss of rhodopsin function, whereas the dominant conditions are a consequence of gain of function and/or dominant negative activity. The in-depth characterisation of many rhodopsin mutations has revealed that there are distinct consequences on the protein structure and function associated with different mutations. Here we categorise rhodopsin mutations into seven discrete classes; with defects ranging from misfolding and disruption of proteostasis, through mislocalisation and disrupted intracellular traffic to instability and altered function. Rhodopsin adRP offers a unique paradigm to understand how disturbances in photoreceptor homeostasis can lead to neuronal cell death. Furthermore, a wide range of therapies have been tested in rhodopsin RP, from gene therapy and gene editing to pharmacological interventions. The understanding of the disease mechanisms associated with rhodopsin RP and the development of targeted therapies offer the potential of treatment for this currently untreatable neurodegeneration.

Mutational Analysis of the Rhodopsin Gene in Sector Retinitis Pigmentosa

BACKGROUND

To determine the role of rhodopsin (RHO) gene mutations in patients with sector retinitis pigmentosa (RP) from Northern Ireland.

DESIGN

A case series of sector RP in a tertiary ocular genetics clinic.

PARTICIPANTS

Four patients with sector RP were recruited from the Royal Victoria Hospital (Belfast, Northern Ireland) and Altnagelvin Hospital (Londonderry, Northern Ireland) following informed consent.

METHODS

The diagnosis of sector RP was based on clinical examination, International Society for Clinical Electrophysiology of Vision (ISCEV) standard electrophysiology, and visual field analysis. DNA was extracted from peripheral blood leucocytes and the coding regions and adjacent flanking intronic sequences of the RHO gene were polymerase chain reaction (PCR) amplified and cycle sequenced.

MAIN OUTCOME MEASURE

Rhodopsin mutational status.

RESULTS

A heterozygous missense mutation in RHO (c.173C > T) resulting in a non-conservative substitution of threonine to methionine (p. Thr58Met) was identified in one patient and was absent from 360 control individuals. This non-conservative substitution (p.Thr58Met) replaces a highly evolutionary conserved polar hydrophilic threonine residue with a non-polar hydrophobic methionine residue at position 58 near the cytoplasmic border of helix A of RHO.

CONCLUSIONS

The study identified a RHO gene mutation (p.Thr58Met) not previously reported in RP in a patient with sector RP. These findings outline the phenotypic variability associated with RHO mutations. It has been proposed that the regional effects of RHO mutations are likely to result from interplay between mutant alleles and other genetic, epigenetic and environmental factors.

Phospholipid Bicelles Improve the Conformational Stability of Rhodopsin Mutants Associated with Retinitis Pigmentosa

Mutations in the visual photoreceptor rhodopsin are the cause of the retinal degenerative disease retinitis pigmentosa. Some naturally occurring mutations can lead to protein conformational instability. Two such mutations, N55K and G90V, in the first and second transmembrane helices of the receptor, have been associated with sector and classical retinitis pigmentosa, respectively, and showed enhanced thermal sensitivity. We have carefully analyzed the effect of phospholipid bicelles on the stability and ligand binding properties of these two mutants and compared it with those of the detergent-solubilized samples. We have used a phospholipid bilayer consisting of 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine (DMPC) and 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC). We find that DMPC/DHPC bicelles dramatically increase the thermal stability of the rhodopsin mutants G90V and N55K. The chromophore stability and regeneration of the mutants were also increased in bicelles when compared to their behavior in a dodecyl maltoside detergent solution. The retinal release process was slowed in bicelles, and chromophore entry, after illumination, was improved for the G90V mutant but not for N55K. Furthermore, fluorescence spectroscopy measurements showed that bicelles allowed more exogenous retinal binding to the photoactivated G90V mutant than in a detergent solution. In contrast, N55K could not reposition any chromophore either in the detergent or in bicelles. The results demonstrate that DMPC/DHPC bicelles can counteract the destabilizing effect of the disease-causing mutations and can modulate the structural changes in the ensuing receptor photoactivation in a distinct specific manner for different retinitis pigmentosa mutant phenotypes.

[Retinitis pigmentosa in an adolescent]

BACKGROUND

Retinitis pigmentosa is the most common chronic and inherited condition of retinal dystrophy. The progressive involvement of retinal photoreceptors and other layers characterize this condition. This situation results in optic disc pallor and retinal pigment deposition vascular attenuation.

CASE REPORT

We present the case of a 15-year-old male with a history of 6 months evolution characterized by night blindness and bilateral impairment of superior temporal vision.

CONCLUSIONS

This type of dystrophy is a genetic and progressive eye condition that begins during adolescence and produces visual impairment.

Differential light-induced responses in sectorial inherited retinal degeneration

Retinitis pigmentosa (RP) is a group of genetically and clinically heterogeneous inherited degenerative retinopathies caused by abnormalities of photoreceptors or retinal pigment epithelium in the retina leading to progressive sight loss. Rhodopsin is the prototypical G-protein-coupled receptor located in the vertebrate retina and is responsible for dim light vision. Here, novel M39R and N55K variants were identified as causing an intriguing sector phenotype of RP in affected patients, with selective degeneration in the inferior retina. To gain insights into the molecular aspects associated with this sector RP phenotype, whose molecular mechanism remains elusive, the mutations were constructed by site-directed mutagenesis, expressed in heterologous systems, and studied by biochemical, spectroscopic, and functional assays. M39R and N55K opsins had variable degrees of chromophore regeneration when compared with WT opsin but showed no gross structural misfolding or altered trafficking. M39R showed a faster rate for transducin activation than WT rhodopsin with a faster metarhodopsinII decay, whereas N55K presented a reduced activation rate and an altered photobleaching pattern. N55K also showed an altered retinal release from the opsin binding pocket upon light exposure, affecting its optimal functional response. Our data suggest that these sector RP mutations cause different protein phenotypes that may be related to their different clinical progression. Overall, these findings illuminate the molecular mechanisms of sector RP associated with rhodopsin mutations.

Rhodopsin p.N78I dominant mutation causing sectorial retinitis pigmentosa in a pedigree with intrafamilial clinical heterogeneity

OBJECTIVE

The purpose of this study was to determine the molecular basis of retinitis pigmentosa (RP) in a 4 affected sib-family segregating this retinal phenotype.

METHODS

Affected sibs underwent complete ophthalmologic examination including funduscopic inspection, electroretinogram, fluorescein angiography, visual field measurement, and optical coherence tomography. Both parents were deceased after their sixties and were reported with no visual handicap. Molecular analysis included direct nucleotide sequencing of the rhodopsin gene (RHO), at chromosome 3q21-q24, in DNA from a total of 4 affected sibs. A total of 200 ethnically matched alleles were included as mutation controls.

RESULTS

Sector RP was clinically documented in this family. Wide phenotypic variability was observed with visual acuities ranging from 20/20 to 20/200 and variable funduscopic appearance. Molecular analysis disclosed a c.233A>T mutation at RHO exon 1, predicting a missense p.N78I substitution.

CONCLUSIONS

Even though RP can be caused by mutations in a variety of genes, the RHO gene was chosen to be investigated in this RP family since it has been previously associated to sector disease. This case exemplifies the value of guiding RP molecular analysis based on funduscopic features.