RDH5-Related Fundus Albipunctatus in a Large Japanese Cohort

RDH5 and RLBP1-Associated Inherited Retinal Diseases: Refining the Spectrum of Stationary and Progressive Phenotypes

PURPOSE

To investigate the clinical, functional, and imaging characteristics in patients affected by inherited retinal diseases associated with RDH5 and RLBP1 gene variants, and to report novel genotype-phenotype correlations.

DESIGN

Retrospective single-center cohort study.

METHODS

Twenty-two patients with molecularly confirmed RLBP1-associated retinopathy and 5 with RDH5-associated retinopathy. Medical records were reviewed to obtain data on family history and ophthalmologic examinations, including retinal imaging and full-field electroretinography (ffERG). Genotype was determined by targeted next-generation sequencing followed by confirmation and familial segregation by Sanger sequencing.

RESULTS

The median (interquartile ranges) age at baseline for the RDH5 and RLBP1 cohort was 44.6 (38.2-67.9) years and 36.9 (23.1-45.2) years, respectively. Macular atrophy (MA) was found in approximately 80% of eyes from both cohorts. The RLBP1 genotype was associated with a lower macular volume by 0.28 mm3 (95% CI, -0.46 to -0.11; P = .005) compared to the RDH5 genotype. In both genotypic cohorts, we found a significant annual rate of macular volume loss, estimated at -0.007 mm3/y (95% CI, -0.012 to -0.001; P = .02), without any significant difference between the two genotypes. Three unrelated patients homozygous for the c.361C>T p.(Arg121Trp) RLBP1 variant showed minimal impairment of both the rod and cone systems function on ffERG and absence of MA.

CONCLUSIONS

Progressive MA in addition to congenital night blindness can be identified in adult patients with RDH5-associated retinopathy. Vice versa, hypomorphic RLBP1 variants may cause milder retinal phenotypes rather than the typical severe rod-cone dystrophy with MA. These findings could prove beneficial to improve the prognostication of patients and help in designing future interventional trials.

One-Year Outcomes of Oral Treatment With Alga Capsules Containing Low Levels of 9-cis-β-Carotene in RDH5-Related Fundus Albipunctatus

PURPOSE

This study aimed to clarify the effect of 1-year oral treatment with 9-cis-β-carotene-rich alga Dunaliella bardawil (Dunaliella supplementation) using full-field electroretinography (ERG) in patients with RDH5-related fundus albipunctatus (FAP).

DESIGN

Prospective, interventional case series.

PARTICIPANTS

The study included 12 patients (23 eyes) with RDH5-related FAP.

METHODS

Twelve patients (23 eyes) with RDH5-related FAP received Dunaliella supplementation (total daily dose of β-carotene was 74.0 mg, comprising 28.4 mg 9-cis-β-carotene and 45.6 mg all-trans-β-carotene at a ratio of 1:1.6) for 1 year and underwent ophthalmic examinations, including full-field ERG at baseline, 3 months, and 1 year after the initial treatment.

MAIN OUTCOME MEASURES

The main outcome was changes in the amplitudes of responses of full-field ERG before and after treatment. A linear mixed-effects model was used to evaluate the adjusted mean difference between the amplitude of each response pretreatment and posttreatment.

RESULTS

Prolonged dark adaptation (DA) responses at 3 months revealed a significant impairment in the b-wave of DA 0.01 (adjusted mean difference, -34.7, 95% CI, -66.8 to -2.73, P = .041) and a-wave of DA 3.0 (-29.0, 95% CI, -50.6 to -7.41, P = .013) and DA 10.0 (-40.4, 95% CI, -67.8 to -13.0, P = .007), which were also observed at 1 year. Additionally, prolonged DA and light adaptation (LA) responses revealed statistically significant impairment at 1 year in the b-wave of DA 3.0 (-43.8, 95% CI, -82.9 to -4.78, P = .035), DA 10.0 (-59.7, 95% CI, -101.8 to -17.61, P = .009), LA 3.0 (-7.31, 95% CI, -13.6 to -1.04, P = .029), and LA 3.0 flicker (-7.53, 95% CI, -12.7 to -2.34, P = .007).

CONCLUSIONS

Our study results suggest that Dunaliella supplementation comprising low levels of 9-cis-β-carotene compared with those reported in a previous study (1:1 ratio) adversely affects ERG amplitudes in patients with RDH5-related FAP.

The downregulation of HSP90-controlled CRALBP expression is associated with age-related vision attenuation

The dysfunction of CRALBP, a key regulator of the visual cycle, is associated with retinitis punctata albescens characterized by night vision loss and retinal degeneration. In this paper, we find that the expression of CRALBP is regulated by heat shock protein 90 (HSP90). Inhibition of HSP90α or HSP90β expression by using the CRISPR-Cas9 technology downregulates CRALBP's mRNA and protein expression in ARPE-19 cells by triggering the degradation of transcription factor SP1 in the ubiquitin-proteasome pathway. SP1 can bind to CRALBP's promoter, and inhibition of SP1 by its inhibitor plicamycin or siRNA downregulates CRALBP's mRNA expression. In the zebrafish, inhibition of HSP90 by the intraperitoneal injection of IPI504 reduces the thickness of the retinal outer nuclear layer and Rlbp1b mRNA expression. Interestingly, the expression of HSP90, SP1, and CRALBP is correlatedly downregulated in the senescent ARPE-19 and Pig primary RPE cells in vitro and in the aged zebrafish and mouse retinal tissues in vivo. The aged mice exhibit the low night adaption activity. Taken together, these data indicate that the HSP90-SP1 is a novel regulatory axis of CRALBP transcriptional expression in RPE cells. The age-mediated downregulation of the HSP90-SP1-CRALBP axis is a potential etiology for the night vision reduction in senior people.

Selection signature analysis reveals RDH5 performed key function in vision during sheep domestication process

Abstract. As one of the most successful domesticated animals in the Neolithic age, sheep gradually migrated all over the world with human activities. During the domestication process, remarkable changes have taken place in morphology, physiology, and behavior, resulting in different breeds with different characters via artificial and natural selection. However, the genetic background responsible for these phenotypic variations remains largely unclear. Here, we used whole genome resequencing technology to compare and analyze the genome differences between Asiatic mouflon wild sheep (Ovis orientalis) and Hu sheep (Ovis aries). A total of 755 genes were positively selected in the process of domestication and selection, and the genes related to sensory perception had directional evolution in the autosomal region, such as OPRL1, LEF1, TAS1R3, ATF6, VSX2, MYO1A, RDH5, and some novel genes. A missense mutation of c.T722C/p.M241T in exon 4 of RDH5 existing in sheep were found, and the T allele was completely fixed in Hu sheep. In addition, the mutation with the C allele reduced the retinol dehydrogenase activity encoding by RDH5, which can impair retinoic acid metabolism and further influenced the visual cycle. Overall, our results showed significant enrichment for positively selected genes involved in sensory perception development during sheep domestication; RDH5 and its variants may be related to the retinal degeneration in sheep. We infer that the wild sheep ancestors with weaker visual sensitivity were weeded out by humans, and the mutation was selective, swept by the dual pressures of natural and artificial selection.

Cellular and Molecular Mechanisms of Pathogenesis Underlying Inherited Retinal Dystrophies

Inherited retinal dystrophies (IRDs) are congenital retinal degenerative diseases that have various inheritance patterns, including dominant, recessive, X-linked, and mitochondrial. These diseases are most often the result of defects in rod and/or cone photoreceptor and retinal pigment epithelium function, development, or both. The genes associated with these diseases, when mutated, produce altered protein products that have downstream effects in pathways critical to vision, including phototransduction, the visual cycle, photoreceptor development, cellular respiration, and retinal homeostasis. The aim of this manuscript is to provide a comprehensive review of the underlying molecular mechanisms of pathogenesis of IRDs by delving into many of the genes associated with IRD development, their protein products, and the pathways interrupted by genetic mutation.

Bilateral compressive optic neuropathy and outer retinopathy due to optic canal hyperostosis in a child with isolated vitamin a deficiency

PURPOSE

Vitamin A plays a crucial role in rod phototransduction, with deficient levels manifesting as night blindness. Animal models have demonstrated bone dysplasia in the setting of hypovitaminosis A. We present a rare case of bony overgrowth leading to bilateral compressive optic neuropathy, combined with outer retinopathy, in a paediatric patient secondary to isolated vitamin A deficiency.

METHODS

A single case report was conducted from Toronto, Canada.

RESULTS

A 12-year-old boy with known autism spectrum disorder presented with a 9-month history of progressive painless vision loss. Vision was 20/300 and hand motion in the right and left eye, respectively. Fundus photography demonstrated bilateral optic atrophy and yellow lesions notably in the right eye far periphery. Optical coherence tomography (OCT) imaging demonstrated thinning of the retinal nerve fibre layer, alterations in the ellipsoid zone, as well as retinal pigment epithelium deposits. Computed tomography imaging demonstrated sphenoid bone thickening with narrow optic canals and moderate optic atrophy bilaterally. Full-field electroretinogram (ERG) demonstrated mildly reduced dark adapted (DA) 0.01 b-wave amplitudes and electronegative configuration of DA 3.0 and DA 10.0 ERG; the light adapted ERGs were normal. The patient was treated with pulse vitamin A therapy. Subsequently, the DA ERG normalized, outer retinal changes reversed and vision stabilised; no surgical intervention was conducted.

CONCLUSION

This case represents a rare presentation of compressive optic neuropathy with concomitant outer retinopathy secondary to isolated vitamin A deficiency. Despite improvement in outer retinal integrity on OCT imaging and ERG testing results following vitamin A supplementation, no functional improvement was obtained due to severe optic atrophy.

THE TARGET SIGN: A Near Infrared Feature and Multimodal Imaging in a Pluri-Ethnic Cohort with RDH5-Related Fundus Albipunctatus

PURPOSE

Retinol dehydrogenase 5 (RDH5)-related fundus albipunctatus can present with phenotypic variability. Our purpose was to investigate new clinical characteristics and multimodal imaging findings in patients from different ethnic origins, carrying different mutations.

METHODS

Multicenter international retrospective case series of 18 patients with genetically confirmed RDH5-related fundus albipunctatus. Patients' files were reviewed for fundus images, visual acuity, macular optical coherence tomography scans, near-infrared images, fundus autofluorescence, electroretinogram, and genetic mutations. Imaging and electroretinogram findings.

RESULTS

All eyes (n = 36, 100%) showed small circular findings seen on near-infrared images, termed as the "target sign," correlating to the yellowish dots seen clinically and to the distinct hyperreflective linear lesions on optical coherence tomography at the level between external limiting membrane and retinal pigment epithelium. Perifoveal atrophy with foveal sparing was seen in 4 eyes of 2 patients (both RDH5-c.160C>T, p.R54X mutation). Fundus autofluorescence revealed small hyperautofluorescent dots (n = 16, 44.4%). Scotopic electroretinograms were significantly reduced in all cases with an electronegative pattern, 66.7% displayed cone dysfunction.

CONCLUSION

Our results show distinct imaging findings present in all patients with fundus albipunctatus independent of ethnicity or genetic mutation. Our results can facilitate the current algorithm to diagnose RDH5-related fundus albipunctatus and allow for targeted genetic testing.

Clinical characterization of autosomal dominant retinitis pigmentosa with NRL mutation in a three-generation Japanese family

PURPOSE

Retinitis pigmentosa (RP) is a heterogeneous group of inherited retinal disorders. NRL-associated autosomal dominant (AD)-RP is a rare form of AD-RP in the Japanese population. This study aimed to report a clinical characterization of NRL-associated retinopathy in a three-generation Japanese family.

CASE PRESENTATION

A total of 4 patients from a Japanese family were referred to The Jikei University School of Medicine for clinical and genetic examination. The patients included a male proband (41 years old), his daughters (5 and 6 years old), and his mother (71 years old); they underwent ophthalmic examinations, and genetic testing was performed using whole exome sequencing analysis, revealing a known variant [c.152C > T (p.Pro51Leu)] heterozygously in exon 2 of the NRL gene. Fundus photograph showed that retinal degeneration expanded to the macular and peripheral retina in an age-dependent manner. Fundus autofluorescence imaging showed hyper-autofluorescence (AF) within the macular with slightly hypo-AF in younger patients and obvious hypo-AF in older patients. Optical coherence tomography showed that the length of the ellipsoid zone tended to be longer in younger patients than in older patients. Goldmann perimetry showed an age-dependent decrease in the visual field. Furthermore, full-field electroretinographic findings revealed non-recordable rod and cone function in older patients and non-recordable rod function with preserved cone function in younger patients.

CONCLUSIONS

Our results indicated that retinal construction and function were aggravated in an age-dependent manner, and retinal degeneration, especially in the macular region, revealed milder findings than in previous cases with NRL-associated AD-RP.

A large animal model of RDH5-associated retinopathy recapitulates important features of the human phenotype

Pathogenic variants in retinol dehydrogenase 5 (RDH5) attenuate supply of 11-cis-retinal to photoreceptors leading to a range of clinical phenotypes including night blindness because of markedly slowed rod dark adaptation and in some patients, macular atrophy. Current animal models (such as Rdh5-/- mice) fail to recapitulate the functional or degenerative phenotype. Addressing this need for a relevant animal model we present a new domestic cat model with a loss-of-function missense mutation in RDH5 (c.542G > T; p.Gly181Val). As with patients, affected cats have a marked delay in recovery of dark adaptation. In addition, the cats develop a degeneration of the area centralis (equivalent to the human macula). This recapitulates the development of macular atrophy that is reported in a subset of patients with RDH5 mutations and is shown in this paper in seven patients with biallelic RDH5 mutations. There is notable variability in the age at onset of the area centralis changes in the cat, with most developing changes as juveniles but some not showing changes over the first few years of age. There is similar variability in development of macular atrophy in patients and while age is a risk factor, it is hypothesized that genetic modifying loci influence disease severity, and we suspect the same is true in the cat model. This novel cat model provides opportunities to improve molecular understanding of macular atrophy and test therapeutic interventions for RDH5-associated retinopathies.

A Novel Pathogenic Variant in the RDH5 Gene in a Patient with Fundus Albipunctatus and Severe Macular Atrophy

Purpose

To report a novel 11-cis retinol dehydrogenase gene (RDH5) variant discovered in a 57-year-old male with fundus albipunctatus (FA) complicated by severe macular atrophy.

Methods

The patient was evaluated with a complete ophthalmic examination, optical coherence tomography (OCT), color fundus photography, green wavelength fundus autofluorescence, visual field testing, full-field ERG (ffERG), and multifocal ERG (mfERG). Genetic analysis investigating gene variants involved in inherited retinal disorders was performed.

Results

The patient presented with a rapid decline in visual acuity and a history of poor night vision. On fundoscopy, he exhibited a phenotype characteristic of FA accompanied by severe macular atrophy bilaterally. Heterozygous variants in the RDH5 gene were identified, including a novel missense variant, c.814_815del (p.Leu272Aspfs^∗63), and a known pathogenic nonsense variant, c.160C > T (p.Arg54^∗). Fundus autofluorescence demonstrated bull's eye maculopathy and hyperautofluorescent perifoveal rings bilaterally. OCT showed foveal atrophy of the outer retina and scattered hyper-reflective lesions in the peripheral macula. The ffERG results showed a severely diminished scotopic and photopic response. The mfERG results demonstrated minimal response in the central macula.

Conclusions

Fundus albipunctatus is a rare, congenital form of stationary night blindness caused almost exclusively by the RDH5 gene. This patient's clinical presentation, diagnostic studies, and genetic testing confirmed the diagnosis of FA. Additionally, he exhibited severe macular atrophy, not typically found in FA. Two RDH5 gene variants were identified, one of which is the novel variant, c.814_815del (p.Leu272Aspfs^∗63). We suggest that this RDH5 genotype may be associated with a more progressive phenotype of FA contributing to macular atrophy.

The Role of Vitamin A in Retinal Diseases

Vitamin A is an essential fat-soluble vitamin that occurs in various chemical forms. It is essential for several physiological processes. Either hyper- or hypovitaminosis can be harmful. One of the most important vitamin A functions is its involvement in visual phototransduction, where it serves as the crucial part of photopigment, the first molecule in the process of transforming photons of light into electrical signals. In this process, large quantities of vitamin A in the form of 11-cis-retinal are being isomerized to all-trans-retinal and then quickly recycled back to 11-cis-retinal. Complex machinery of transporters and enzymes is involved in this process (i.e., the visual cycle). Any fault in the machinery may not only reduce the efficiency of visual detection but also cause the accumulation of toxic chemicals in the retina. This review provides a comprehensive overview of diseases that are directly or indirectly connected with vitamin A pathways in the retina. It includes the pathophysiological background and clinical presentation of each disease and summarizes the already existing therapeutic and prospective interventions.

Genetic analysis of consanguineous Pakistani families with congenital stationary night blindness

AIM

Congenital stationary night blindness (CSNB) is a rare, largely non progressive, inherited retinal disorder that can be clinically classified on the basis of fundus and electroretinogram (ERG) abnormalities.

METHODS

We analyzed four large consanguineous families from the Southern Punjab region of Pakistan including multiple individuals affected with CSNB. Exome sequencing (ES) was performed in probands of all four families; Sanger sequencing was performed in additional members to test co-segregation of the variants identified.

RESULTS

We identified two novel and likely pathogenic variants in two pedigrees, namely NM_002905.4:c.668A>C (p.Gln223Pro) in RDH5, and NM_022567.2:c.908del (p.Gly303ValfsTer45) in NYX. In the two other families, the variants NM_002905.4:c.319G>C (p.Gly107Arg) in RDH5 and NM_000541.5:c.874C>T (p.Arg292Ter) in SAG were identified. These variants have been reported previously, but not in the Pakistani population.

CONCLUSIONS

Our findings expand the mutational spectrum of CSNB, in particular within the population of Southern Punjab.

Acquired night blindness due to rod dysfunction after long-term hemodialysis

PURPOSE

To report the clinical findings in 6 patients who developed night blindness after long-term hemodialysis.

STUDY DESIGN

Retrospective case series.

PATIENTS AND METHODS

The medical charts of the 6 patients were examined. The fundus photographs, spectral-domain optical coherence tomographic (SD-OCT) images, full-field ERGs, and blood chemistry panels were analyzed.

RESULTS

The mean age of the 6 patients (4 men) at the time of diagnosis was 69.1 ± 5.9 years. The mean duration of the hemodialysis was 21.8 ± 13.4 years (7-41 years). The visual acuity of the patients was preserved at 20/30 or better except in 1 eye. Ophthalmoscopy showed white flecks that were scattered over the midperipheral retina in all the eyes. SD-OCT showed mild macular degeneration in 5 eyes. The scotopic ERGs elicited by dim flashes were absent, and those elicited by bright flashes had negative waveforms. The photopic ERGs were relatively well preserved. These data indicated a rod-specific dysfunction that may account for the night blindness. The plasma concentration of vitamin A was within the normal range in 4 of the patients and slightly lower than the normal limit in 1 of the patients. Administration of vitamin A was performed for 1 patient, and the symptom of night blindness and scotopic ERGs were improved 3 months later.

DISCUSSION

Long-term hemodialysis can be associated with the night blindness that may be caused by vitamin A deficiency, even though the plasma concentration of vitamin A in these patients was within the normal range.

Genotype-Phenotype Correlations in RP1-Associated Retinal Dystrophies: A Multi-Center Cohort Study in JAPAN

Background: Little is known about genotype–phenotype correlations of RP1-associated retinal dystrophies in the Japanese population. We aimed to investigate the genetic spectrum of RP1 variants and provide a detailed description of the clinical findings in Japanese patients. Methods: In total, 607 patients with inherited retinal diseases were examined using whole-exome/whole-genome sequencing (WES/WGS). PCR-based screening for an Alu element insertion (c.4052_4053ins328/p.Tyr1352AlafsTer9) was performed in 18 patients with autosomal-recessive (AR)-retinitis pigmentosa (RP) or AR-cone dystrophy (COD)/cone-rod dystrophy (CORD), including seven patients with heterozygous RP1 variants identified by WES/WGS analysis, and 11 early onset AR-RP patients, in whom no pathogenic variant was identified. We clinically examined 25 patients (23 families) with pathogenic RP1 variants, including five patients (five families) with autosomal-dominant (AD)-RP, 13 patients (11 families) with AR-RP, and seven patients (seven families) with AR-COD/CORD. Results: We identified 18 pathogenic RP1 variants, including seven novel variants. Interestingly, the Alu element insertion was the most frequent variant (32.0%, 16/50 alleles). The clinical findings revealed that the age at onset and disease progression occurred significantly earlier and faster in AR-RP patients compared to AD-RP or AR-COD/CORD patients. Conclusions: Our results suggest a genotype–phenotype correlation between variant types/locations and phenotypes (AD-RP, AR-RP, and AR-COD/CORD), and the Alu element insertion was the most major variant in Japanese patients with RP1-associated retinal dystrophies.

Clinical characteristics, imaging findings, and genetic results of a patient with CEP290-related cone-rod dystrophy

PURPOSE

To describe the clinical characteristics, the imaging findings, and the genetic results of a patient with cone-rod dystrophy (CORD) related to mutations in CEP290.

METHODS

A case report of atypical CEP290-related CORD. Ophthalmological examination was performed, including best-corrected visual acuity (BCVA), fundus photography, fundus autofluorescence (FAF) imaging, optical coherence tomography (OCT), a visual field test, and electroretinography testing. The genetic test was performed by next-generation sequencing (NGS)-based panel test containing 336 genes.

RESULTS

A 57-year-old female who had reported a visual loss for 5 years. BCVA was 20/100 in both eyes. The fundus examination revealed a hypopigmented halo around the fovea, showing a paracentral hyperautofluorescent ring on FAF. OCT demonstrated the presence of atrophy in the outer retinal layers. The genetic test identified the probably pathogenic variants c.4028delA and c.5254C>T in compound heterozygosis in CEP290.

CONCLUSIONS

This is the first report to present the clinical characteristics, imaging findings, and genetic test results of a patient with CEP290-related CORD. Our case contributes to expanding the clinical involvement of CEP290 pathogenic variants. This study indicates that CEP290-related CORD may have a mild phenotype with late-onset dystrophy, making these patients interesting candidates for innovative treatments such as genetic therapeutic approaches.

Complete congenital stationary night blindness associated with a novel NYX variant (p.Asn216Lys) in middle-aged and older adult patients

BACKGROUND

Complete congenital stationary night blindness (CSNB) is a retinal disorder thought to be non-progressive. The purpose of this study was to characterize the clinical and genetic findings of middle-aged and older adult patients with X-linked complete CSNB.

METHODS

Three male CSNB patients (aged 62, 72, and 51 years) and one unaffected female carrier in a Japanese family were included in this study. Whole-exome sequencing (WES) was performed to determine the disease-causing variants. Co-segregation was confirmed in the family members. We performed a comprehensive ophthalmic examination on each patient.

RESULTS

In the 62-year-old patient, a novel hemizygous variant (c.648 C > A; p.Asn216Lys) of the NYX gene was identified by WES analysis. The other two patients carried the variant hemizygously, and the unaffected carrier harbored the variant heterozygously. The clinical and electroretinography (ERG) findings were very similar among all three patients. Fundus images exhibited high myopic chorioretinal atrophy with long axial length. Ultra-wide field fundus autofluorescence images showed no retinal degenerative changes except for changes resulting from high myopia and previous retinal diseases. The ERG findings showed no response in rod ERG, electronegative configuration with preserved a-waves in standard/bright-flash ERG, and preserved responses in cone and 30-Hz flicker ERG, which were compared with age-matched controls with high myopia.

CONCLUSIONS

We identified a novel missense NYX variant in a Japanese family with complete CSNB. Our clinical findings indicated that photoreceptor mediated ERG responses are well preserved even in middle-aged and older adult patients.

Vitamin A deficiency after prolonged intake of an unbalanced diet in a Japanese hemodialysis patient

BACKGROUND

In industrialized countries, vitamin A deficiency (VAD) is extremely rare, except association with bariatric surgeries and hepatobiliary disorders. It is unusual that VAD develops during hemodialysis due to reduced glomerular filtration of vitamin A-binding protein. We reported the case of a 58-year-old Japanese male hemodialysis patient diagnosed with VAD.

CASE PRESENTATION

The patient undergoing hemodialysis for more than 15 years presented with progressive photophobia and night blindness and was ophthalmologically examined. He denied a history of cancer or hepatobiliary disease and reported that he loved eating prepackaged noodle bowls and foods, with prolonged low intake of fruits/vegetables. He had good visual acuity. Fundus images showed numerous white dots in the midperipheral retinae, but no degenerative changes. In baseline full-field electroretinography (ERG), b-wave responses were extremely reduced in rod ERG, a-wave amplitudes in standard-flash/strong-flash ERG were reduced to 20-25% of our controls, a- and b-wave amplitudes in cone ERG were reduced to 40-50% of the controls. Whole-exome sequencing identified no pathogenic variant for any inherited retinal disorder. He was diagnosed with VAD because of reduced serum vitamin A levels and treated with retinol palmitate. Two months after treatment commencement, the serum vitamin A level was within the normal range. Full-field ERG showed that the scotopic ERG responses markedly improved compared with baseline.

CONCLUSIONS

This is the first report of VAD associated with undernutrition in the Japanese hemodialysis population.

Novel biallelic TRPM1 variants in an elderly patient with complete congenital stationary night blindness

BACKGROUND

Little is known about whether patients with complete congenital stationary night blindness (CSNB) maintain visual function throughout their lifetime. The purpose of this report was to describe clinical and genetic features of an elderly female patient with complete CSNB that we followed for 5 years.

METHODS

Molecular genetic analysis using whole-exome sequencing (WES) was performed to detect disease-causing variants. We performed a comprehensive ophthalmic examination including full-field electroretinography (ERG).

RESULTS

In the patient, WES identified two novel variants (c.1034delT; p.Phe345SerfsTer16 and c.1880T>A; p.Met627Lys) in the TRPM1 gene. Her unaffected daughter has one of the variants. The patient reported that her visual acuity has remained unchanged since elementary school. At the age of 68 years old, fundus and fundus autofluorescence imaging showed no remarkable findings except for mild myopic changes. Goldmann perimetry showed preserved visual fields with all V-4e, I-4e, I-3e and I-2e isopters. Optical coherence tomography demonstrated preserved retinal thickness and lamination. Rod ERG showed no response; bright-flash ERG showed an electronegative configuration with minimally reduced a-waves, and cone and 30-Hz flicker ERG showed minimally reduced responses. Overall, the ERG findings of ON bipolar pathway dysfunction were consistent with complete CSNB.

CONCLUSIONS

This is the oldest reported patient with complete CSNB and biallelic TRPM1 variants. Our ophthalmic findings suggest that some patients with TRPM1-related CSNB may exhibit preserved retinal function later in life.

Genetic defects of CHM and visual acuity outcome in 24 choroideremia patients from 16 Japanese families

Choroideremia (CHM) is an incurable progressive chorioretinal dystrophy. Little is known about the natural disease course of visual acuity in the Japanese population. We aimed to investigate the genetic spectrum of the CHM gene and visual acuity outcomes in 24 CHM patients from 16 Japanese families. We measured decimal best-corrected visual acuity (BCVA) at presentation and follow-up, converted to logMAR units for statistical analysis. Sanger and/or whole-exome sequencing were performed to identify pathogenic CHM variants/deletions. The median age at presentation was 37.0 years (range, 5–76 years). The mean follow-up interval was 8.2 years. BCVA of the better-seeing eye at presentation was significantly worsened with increasing age (r = 0.515, p < 0.01), with a high rate of BCVA decline in patients > 40 years old. A Kaplan–Meier survival curve suggested that a BCVA of Snellen equivalent 20/40 at follow-up remains until the fifties. Fourteen pathogenic variants, 6 of which were novel [c.49 + 5G > A, c.116 + 5G > A, p.(Gly176Glu, Glu177Ter), p.Tyr531Ter, an exon 2 deletion, and a 5.0-Mb deletion], were identified in 15 families. No variant was found in one family only. Our BCVA outcome data are useful for predicting visual prognosis and determining the timing of intervention in Japanese patients with CHM variants.

RP2-associated retinal disorder in a Japanese cohort: Report of novel variants and a literature review, identifying a genotype-phenotype association

The retinitis pigmentosa 2 (RP2) gene is one of the causative genes for X-linked inherited retinal disorder. We characterized the clinical/genetic features of four patients with RP2-associated retinal disorder (RP2-RD) from four Japanese families in a nationwide cohort. A systematic review of RP2-RD in the Japanese population was also performed. All four patients were clinically diagnosed with retinitis pigmentosa (RP). The mean age at examination was 36.5 (10-47) years, and the mean visual acuity in the right/left eye was 1.40 (0.52-2.0)/1.10 (0.52-1.7) in the logarithm of the minimum angle of resolution unit, respectively. Three patients showed extensive retinal atrophy with macular involvement, and one had central retinal atrophy. Four RP2 variants were identified, including two novel missense (p.Ser6Phe, p.Leu189Pro) and two previously reported truncating variants (p.Arg120Ter, p.Glu269CysfsTer3). The phenotypes of two patients with truncating variants were more severe than the phenotypes of two patients with missense variants. A systematic review revealed additional 11 variants, including three missense and eight deleterious (null) variants, and a statistically significant association between phenotype severity and genotype severity was revealed. The clinical and genetic spectrum of RP2-RD was illustrated in the Japanese population, identifying the characteristic features of a severe form of RP with early macular involvement.