Cone-rod Dystrophy Research Articles

Clinical Phenotypes of CDHR1-Associated Retinal Dystrophies.

The retinal dystrophy phenotype associated with CDHR1 retinopathy is clinically heterogenous. In this study, we describe the clinical and molecular findings of a retinal dystrophy cohort (10 patients) attributed to autosomal recessive CDHR1 and report novel variants in populations not previously identified with CDHR1-related retinopathy. Seven patients had evaluations covering at least a three-year period. The mean age of individuals at first symptoms was 36 ± 8.5 years (range 5–45 years). Visual acuity at the last visit ranged from 20/20 to 20/2000 (mean LogMAR 0.8 or 20/125). Three clinical subgroups were identified: rod–cone dystrophy (RCD), cone–rod dystrophy (CRD), and maculopathy. Extinguished scotopic electroretinography responses were noted in the RCD patients. Macular involvement was noted in all patients and documented on color fundus photography, fundus autofluorescence, and optical coherence tomography. Notable asymmetry of the degree of macular atrophy was present in two patients. The possible association between CDHR1 variants and clinical findings was predicted using molecular modeling.

Supernormal rod response mediated by a novel KCNV2 variant in a cone dystrophy type 3B patient

The proband was an 8-year-old boy, complaining of progressively decreased vision in both eyes for 3 years. The electroretinogram was characterized by supernormal rod response. While the responses of the rod and cone system were reduced, the amplitudes of dark-adapted electroretinogram responses at a high intensity were supernormal. A homozygous non-frameshift deletion variant c.1002-1004del (p. L335del) in KCNV2 was found by the Next Generation Sequencing using a custom designed panel. His father was a heterozygous carrier of this variant. In silico analysis indicated the variant was harmful. The proband was diagnosed as cone dystrophy type 3B which also known as cone dystrophy with supernormal rod response.

Rapid Quantification of the Binocular Visual Field for Clinical Trials: Performance of a Modified Esterman Supra-Threshold Test Implemented with the Open Perimetry Interface.

PurposeWe aimed to assess the performance of the modified-Esterman test (mET) as a rapid suprathreshold binocular quantification tool for the assessment of peripheral visual fields. The mET consists of an even spread of test points across the visual field.Materials and MethodsThe mET was implemented on the Octopus 0900 perimeter using the Open Perimetry Interface (OPI) and consisted of 160 points. Patients with choroideremia, a rod-cone dystrophy, Stargardt disease, a cone-rod dystrophy, and healthy volunteers underwent both the mET and the standard Esterman tests twice. Disease severity (mild/moderate/severe) was graded on both tests independently. Voronoi tessellation was utilised to compare the tests.ResultsThe Voronoi visualisation was able to demonstrate that the mET was able to provide more information about the disease state at all stages of diseases. This was confirmed by the agreement statistic, which showed that the mET detected 27% more points of visual field loss compared to the Esterman test, being most useful in patients with rod-cone dystrophies.ConclusionThe mET provides a speedy quantitative measure of the peripheral visual field loss, which can be used in clinical trials to monitor longitudinal assessment of peripheral visual function. The mET provides a more even coverage across the visual field compared to the Esterman test points, making it more suitable for this purpose. This is a key part of safety monitoring in retinal clinical trials. The mET can easily be implemented on commercially available perimeters that allow Open Perimetry.

Bioinformatics Analysis of ABCA4 Variants in Terms of Pathogenicity Prediction

ABCA4 is a retina‐specific member of the ATP‐binding cassette transporter protein family. It is responsible for the transport and clearance of retinal derivatives produced in the visual cycle in the photoreceptor cells. More than a thousand mutations in the ABCA4 gene are associated with a series of autosomal recessive inherited retinal diseases, including Stargardt disease, retinitis pigmentosa, and cone‐rod dystrophy, and also linked with susceptibility for age‐related macular degeneration. Determining disease‐causing variants is a crucial part of clinical management, yet, a limited number of the ABCA4 variants have been studied in vitro and relatively few of them have been functionally characterized. Bioinformatics approaches can be highly effective to interpret the consequences of the mutations more rapidly. In this study, we aim to analyze the pathogenicity of ABCA4 clinical and prospective variants utilizing two methods to infer mutation effects: prediction software and computational protein models. We hypothesize that these two approaches in combination will allow us to identify the consequences of the ABCA4 variants and gain insight into the overall structure and function of the protein. We found that the pathogenicity prediction software results align well with the structural analysis results in most instances. The clinical in silico prediction tools were found to predict pathogenicity more frequently than structural analyses, albeit with high sensitivity and low specificity. On the other hand, structure prediction tools are high specificity and thus, predict more accurately. Our results also indicate a correlation between disease severity and structural changes in protein models induced by genetic variations. Our findings suggest that computational analyses are promising tools to predict pathogenicity and can aid in the understanding of disease‐associated ABCA4 genetic variants. These computational approaches have additional applications in protein analysis and provide a strong framework for future in vitro studies.

Bardet\u2013Biedl syndrome: a case series

BackgroundBardet–Biedl syndrome is a rare multisystem autosomal recessive disorder that falls under the spectrum of ciliopathy disorders. It is characterized by rod–cone dystrophy, renal malformations, polydactyly, learning difficulties, central obesity, and hypogonadism. Many minor features that are related with Bardet–Biedl syndrome might aid in diagnosis and are crucial in clinical management. Bardet–Biedl syndrome is diagnosed on the basis of clinical signs and symptoms, which can be confirmed by genetic testing. Here we present four cases of Bardet–Biedl syndrome. To our knowledge, these are the first cases of Bardet–Biedl syndrome reported from Sudan.Case presentationHere, we report four Sudanese patients who presented with a variety of clinical manifestations of Bardet–Biedl syndrome (two males, 50 and 16 years old; two females, 38 and 18 years old). The first two patients presented with features of chronic kidney disease. The third patient had recently been diagnosed with type 1 diabetes and diabetic ketoacidosis. The fourth patient showed signs of retinal dystrophy early on. Case 1: a 38-year-old female presented with vomiting and irritability; the patient was diagnosed with Bardet–Biedl syndrome as she fulfilled six items of the primary features (obesity, retinitis pigmentosa, post-axial polydactyly, renal abnormalities, learning disabilities, and genitourinary malformations), as well as one secondary feature (cardiovascular involvement, that is, left ventricular hypertrophy). Case 2: a 50-year-old male presented with fatigability; the patient was diagnosed with Bardet–Biedl syndrome as he fulfilled four items of the primary features (obesity, retinitis pigmentosa, post-axial polydactyly, and renal abnormalities) in addition to two secondary features (diabetes mellitus and cardiovascular involvement, that is, left ventricular hypertrophy). Case 3: an 18-year-old female presented with polyuria, polydipsia, weight loss, and epigastric pain for 2 days; the patient was diagnosed with Bardet–Biedl syndrome because he had four major features (retinal dystrophy, post-axial polydactyly, obesity, and learning disabilities) in addition to three secondary features (developmental delay, diabetes mellitus, and strabismus). Case 4: a 16-year-old male presented with a blurring of vision; the patient was diagnosed with Bardet–Biedl syndrome as he exhibited four major features (retinal dystrophy, post-axial polydactyly, obesity, and learning disabilities) plus two secondary features (developmental delay and cataract).ConclusionThe scarcity of Bardet–Biedl syndrome necessitates a high index of suspicion to diagnose this syndrome. Increased awareness among physicians is required for the early diagnosis and treatment of Bardet–Biedl syndrome and to avoid complications and mortality.

Retinal Phenotype of Patients with CLRN1-Associated Usher 3A Syndrome in French Light4Deaf Cohort.

PurposeBiallelic variants in CLRN1 are responsible for Usher syndrome 3A and non-syndromic rod–cone dystrophy (RCD). Retinal findings in Usher syndrome 3A have not been well defined. We report the detailed phenotypic description of RCD associated with CLRN1 variants in a prospective cohort.MethodsPatients were clinically investigated at the National Reference Center for rare ocular diseases at the Quinze-Vingts Hospital, Paris, France. Best-corrected visual acuity (BCVA) tests, Goldmann perimetry, full-field electroretinography (ffERG), retinal photography, near-infrared reflectance, short-wavelength and near-infrared autofluorescence, and optical coherence tomography (OCT) were performed for all patients.ResultsFour patients from four unrelated families were recruited. Mean follow-up was 11 years for three patients, and only baseline data were available for one subject. Median BCVA at baseline was 0.2 logMAR (range, 0.3–0). ffERG responses were undetectable in all subjects. The III4e isopter of the Goldmann visual field was constricted to 10°. The retinal phenotype was consistent in all patients: small whitish granular atrophic areas were organized in a network pattern around the macula and in the midperiphery. OCT showed intraretinal microcysts in all patients. Upon follow-up, all patients experienced a progressive BCVA loss and further visual field constriction. Four distinct pathogenic variants were identified in our patients: two missense (c.144T>G, p.(Asn48Lys) and c.368C>A, p.(Ala123Asp)) and two frameshift variants (c.176del, p.(Gly59Valfs*13) and c.230dup, p.(Ala78Serfs*52)).ConclusionsRCD in Usher 3A syndrome has some distinctive features. It is a severe photoreceptor dystrophy with whitish granular posterior pole appearance and cystic maculopathy.

ABCA4 c.859-25A>G, a Frequent Palestinian Founder Mutation Affecting the Intron 7 Branchpoint, Is Associated With Early-Onset Stargardt Disease.

PurposeThe effect of noncoding variants is often unknown in the absence of functional assays. Here, we characterized an ABCA4 intron 7 variant, c.859-25A>G, identified in Palestinian probands with Stargardt disease (STGD) or cone-rod dystrophy (CRD). We investigated the effect of this variant on the ABCA4 mRNA and retinal phenotype, and its prevalence in Palestine.MethodsThe ABCA4 gene was sequenced completely or partially in 1998 cases with STGD or CRD. The effect of c.859-25A>G on splicing was investigated in silico using SpliceAI and in vitro using splice assays. Homozygosity mapping was performed for 16 affected individuals homozygous for c.859-25A>G. The clinical phenotype was assessed using functional and structural analyses including visual acuity, full-field electroretinography, and multimodal imaging.ResultsThe smMIPs-based ABCA4 sequencing revealed c.859-25A>G in 10 Palestinian probands from Hebron and Jerusalem. SpliceAI predicted a significant effect of this putative branchpoint-inactivating variant on the nearby intron 7 splice acceptor site. Splice assays revealed exon 8 skipping and two partial inclusions of intron 7, each having a deleterious effect. Additional genotyping revealed another 46 affected homozygous or compound heterozygous individuals carrying variant c.859-25A>G. Homozygotes shared a genomic segment of 59.6 to 87.9 kb and showed severe retinal defects on ophthalmoscopic evaluation.ConclusionsThe ABCA4 variant c.859-25A>G disrupts a predicted branchpoint, resulting in protein truncation because of different splice defects, and is associated with early-onset STGD1 when present in homozygosity. This variant was found in 25/525 Palestinian inherited retinal dystrophy probands, representing one of the most frequent inherited retinal disease-causing variants in West-Bank Palestine.

Dawn and dusk peaks of outer segment phagocytosis, and visual cycle function require Rab28.

RAB28 is a farnesylated, ciliary G‐protein. Patient variants in RAB28 are causative of autosomal recessive cone‐rod dystrophy (CRD), an inherited human blindness. In rodent and zebrafish models, the absence of Rab28 results in diminished dawn, photoreceptor, outer segment phagocytosis (OSP). Here, we demonstrate that Rab28 is also required for dusk peaks of OSP, but not for basal OSP levels. This study further elucidated the molecular mechanisms by which Rab28 controls OSP and inherited blindness. Proteomic profiling identified factors whose expression in the eye or whose expression at dawn and dusk peaks of OSP is dysregulated by loss of Rab28. Notably, transgenic overexpression of Rab28, solely in zebrafish cones, rescues the OSP defect in rab28 KO fish, suggesting rab28 gene replacement in cone photoreceptors is sufficient to regulate Rab28‐OSP. Rab28 loss also perturbs function of the visual cycle as retinoid levels of 11‐cRAL, 11cRP, and atRP are significantly reduced in larval and adult rab28 KO retinae (p < .05). These data give further understanding on the molecular mechanisms of RAB28‐associated CRD, highlighting roles of Rab28 in both peaks of OSP, in vitamin A metabolism and in retinoid recycling.

Impact of Reference Center Choice on Adaptive Optics Imaging Cone Mosaic Analysis.

PurposeFoveal center marking is a key step in retinal image analysis. We investigated the discordance between the adaptive optics (AO) montage center (AMC) and the foveal pit center (FPC) and its implications for cone mosaic analysis using a commercial flood-illumination AO camera.MethodsThirty eyes of 30 individuals (including 15 healthy and 15 patients with rod–cone dystrophy) were included. Spectral-domain optical coherence tomography was used to determine the FPC, and flood-illumination AO imaging was performed with overlapping image frames to create an AO montage. The AMC was determined by averaging the (0,0) coordinates in the four paracentral overlapping AO image frames. Cone mosaic measurements at various retinal eccentricities were compared between corresponding retinal loci relative to the AMC or FPC.ResultsAMCs were located temporally to the FPCs in 14 of 15 eyes in both groups. The average AMC–FPC discordance was 0.85° among healthy controls and 0.33° among patients with rod-cone dystrophy (P < 0.05). The distance of the AMC from the FPC was a significant determinant of the cone density (β estimate = 218 cells/deg2/deg; 95% confidence interval [CI], 107–330; P < 0.001) and inter-cone distance (β estimate = 0.28 arcmin/deg; 95% CI, 0.15–0.40; P < 0.001), after adjustment for age, sex, axial length, spherical equivalent, eccentricity, and disease status.ConclusionsThere is a marked mismatch between the AMC and FPC in healthy eyes that may be modified by disease process such as rod–cone dystrophy. We recommend users of AO imaging systems carefully align the AO montage with a foveal anatomical landmark, such as the FPC, to ensure precise and reproducible localization of the eccentricities and regions of interest for cone mosaic analysis.

Functional characterization of variants of unknown significance in a spinocerebellar ataxia patient using an unsupervised machine learning pipeline

CAG-expanded ATXN7 has been previously defined in the pathogenesis of spinocerebellar ataxia type 7 (SCA7), a polyglutamine expansion autosomal dominant cerebellar ataxia. Pathology in SCA7 occurs as a result of a CAG triplet repeat expansion in excess of 37 in the first exon of ATXN7, which encodes ataxin-7. SCA7 presents clinically with spinocerebellar ataxia and cone-rod dystrophy. Here, we present a novel spinocerebellar ataxia variant occurring in a patient with mutations in both ATXN7 and TOP1MT, which encodes mitochondrial topoisomerase I (top1mt). Using machine-guided, unbiased microscopy image analysis, we demonstrate alterations in ataxin-7 subcellular localization, and through high-fidelity measurements of cellular respiration, bioenergetic defects in association with top1mt mutations. We identify ataxin-7 Q35P and top1mt R111W as deleterious mutations, potentially contributing to disease states. We recapitulate our mutations through Drosophila genetic models. Our work provides important insight into the cellular biology of ataxin-7 and top1mt and offers insight into the pathogenesis of spinocerebellar ataxia applicable to multiple subtypes of the illness. Moreover, our study demonstrates an effective pipeline for the characterization of previously unreported genetic variants at the level of cell biology.

The Transition of Photoreceptor Guanylate Cyclase Type 1 to the Active State.

Membrane-bound guanylate cyclases (GCs), which synthesize the second messenger guanosine-3′, 5′-cyclic monophosphate, differ in their activation modes to reach the active state. Hormone peptides bind to the extracellular domain in hormone-receptor-type GCs and trigger a conformational change in the intracellular, cytoplasmic part of the enzyme. Sensory GCs that are present in rod and cone photoreceptor cells have intracellular binding sites for regulatory Ca2+-sensor proteins, named guanylate-cyclase-activating proteins. A rotation model of activation involving an α-helix rotation was described as a common activation motif among hormone-receptor GCs. We tested whether the photoreceptor GC-E underwent an α-helix rotation when reaching the active state. We experimentally simulated such a transitory switch by integrating alanine residues close to the transmembrane region, and compared the effects of alanine integration with the point mutation V902L in GC-E. The V902L mutation is found in patients suffering from retinal cone–rod dystrophies, and leads to a constitutively active state of GC-E. We analyzed the enzymatic catalytic parameters of wild-type and mutant GC-E. Our data showed no involvement of an α-helix rotation when reaching the active state, indicating a difference in hormone receptor GCs. To characterize the protein conformations that represent the transition to the active state, we investigated the protein dynamics by using a computational approach based on all-atom molecular dynamics simulations. We detected a swinging movement of the dimerization domain in the V902L mutant as the critical conformational switch in the cyclase going from the low to high activity state.

Expanding the phenotype of TTLL5-associated retinal dystrophy: a case series

BackgroundInherited retinal dystrophies describe a heterogeneous group of retinal diseases that lead to the irreversible degeneration of rod and cone photoreceptors and eventual blindness. Recessive loss-of-function mutations in Tubulin Tyrosine Ligase Like 5 (TTLL5) represent a recently described cause of inherited cone–rod and cone dystrophy. This study describes the unusual phenotypes of three patients with autosomal recessive mutations in TTLL5. Examination of these patients included funduscopic evaluation, spectral-domain optical coherence tomography, short-wavelength autofluorescence, and full-field electroretinography (ffERG). Genetic diagnoses were confirmed using whole exome capture. Protein modeling of the identified variants was performed to explore potential genotype–phenotype correlations.ResultsGenetic testing revealed five novel variants in TTLL5 in three unrelated patients with retinal dystrophy. Clinical imaging demonstrated features of sectoral cone–rod dystrophy and cone dystrophy, with phenotypic variability seen across all three patients. One patient also developed high-frequency hearing loss during a similar time period as the onset of retinal disease, potentially suggestive of a syndromic disorder. Retinal structure findings were corroborated with functional measures including ffERG findings that supported these diagnoses. Modeling of the five variants suggest that they cause different effects on protein function, providing a potential reason for genotype–phenotype correlation in these patients.ConclusionsThe authors report retinal phenotypic findings in three unrelated patients with novel mutations causing autosomal recessive TTLL5-mediated retinal dystrophy. These findings broaden the understanding of the phenotypes associated with TTLL5-mediated retinal disease and suggest that mutations in TTLL5 should be considered as a potential cause of sectoral retinal dystrophy in addition to cone–rod and cone dystrophies.

Clinical Aspects of a Rare Disease: Bardet Biedl Syndrome

Bardet Biedl syndrome (BBS) is a rare primary ciliopathy with a complex and extremely variable clinical presentation. The core features of the disease are rod-cone dystrophy, postaxial polydactyly, central obesity, urogenital anomalies, learning difficulties and kidney disease, however the impairment of any organ may complicate the clinical picture. Here we report on clinical findings of 25 patients diagnosed with BBS. Our study is the first on a cohort of Romanian BBS patients, aiming to emphasize the complexity of the disease that may have a devastating impact on patients and their families. Thus, an early clinical diagnosis is crucial for anticipation of other system and organ involvement. Periodic follow up, by a multidisciplinary team, may prevent several severe complications, which could accelerate or aggravate the most deleterious aspects of the disease: loss of vision or renal impairment.

Delineating the Molecular and Phenotypic Spectrum of the CNGA3-Related Cone Photoreceptor Disorder in Pakistani Families.

Cone photoreceptor dysfunction represents a clinically heterogenous group of disorders characterized by nystagmus, photophobia, reduced central or color vision, and macular dystrophy. Here, we described the molecular findings and clinical manifestations of achromatopsia, a partial or total absence of color vision, co-segregating with three known missense variants of CNGA3 in three large consanguineous Pakistani families. Fundus examination and optical coherence tomography (OCT) imaging revealed myopia, thin retina, retinal pigment epithelial cells loss at fovea/perifovea, and macular atrophy. Combination of Sanger and whole exome sequencing revealed three known homozygous missense variants (c.827A>G, p.(Asn276Ser); c.847C>T, p.(Arg283Trp); c.1279C>T, p.(Arg427Cys)) in CNGA3, the α-subunit of the cyclic nucleotide-gated cation channel in cone photoreceptor cells. All three variants are predicted to replace evolutionary conserved amino acids, and to be pathogenic by specific in silico programs, consistent with the observed altered membrane targeting of CNGA3 in heterologous cells. Insights from our study will facilitate counseling regarding the molecular and phenotypic landscape of CNGA3-related cone dystrophies.

New COL6A6 Variant Causes Autosomal Dominant Retinitis Pigmentosa in a Four-Generation Family.

PurposeTo report that variants in the gene for a large lamina basal component protein, COL6A6 (collagen type VI alpha 6 chain, Col6α6), linked to chromosome 3p22.1 causes retinitis pigmentosa (RP) in patients with autosomal dominant transmission (adRP).MethodsA positional-cloning approach, whole exome sequencing, and modeling were used. The proband and several affected family members have been phenotyped and followed for over 12 years.ResultsA heterozygous missense variant, c.509C>G (p. Ser170Cys) in exon 2 of COL6A6 (comprised of 36 exons and 2236 amino acids), was observed in a four- generation family and is likely to cause the adRP phenotype. It was identified in 10 affected members. All affected family members had a distinct phenotype: late-onset rod cone dystrophy, with good retained visual acuity, until their late 70s. Immunohistochemistry of human retina showed a dot-like signal at the base of the inner segments of photoreceptors and outer plexiform layer (OPL). The structural modeling of the N7 domain of Col6α6 suggests that the mutant might result in the abnormal cellular localization of collagen VI or malformation of collagen fibers resulting in the loss of its unique filament structure.Conclusions COL6A6 is widely expressed in human tissues and evolutionary conserved. It is thought to interact with a range of extracellular matrix components. Our findings suggest that this form of RP has long-term useful central visual acuity and a mild progression, which are important considerations for patient counseling.

Structural and functional analysis of the human cone-rod homeobox transcription factor.

The cone‐rod homeobox (CRX) protein is a critical K50 homeodomain transcription factor responsible for the differentiation and maintenance of photoreceptor neurons in the vertebrate retina. Mutant alleles in the human gene encoding CRX result in a variety of distinct blinding retinopathies, including retinitis pigmentosa, cone‐rod dystrophy, and Leber congenital amaurosis. Despite the success of using in vitro biochemistry, animal models, and genomics approaches to study this clinically relevant transcription factor over the past 25 years since its initial characterization, there are no high‐resolution structures in the published literature for the CRX protein. In this study, we use bioinformatic approaches and small‐angle X‐ray scattering (SAXS) structural analysis to further understand the biochemical complexity of the human CRX homeodomain (CRX‐HD). We find that the CRX‐HD is a compact, globular monomer in solution that can specifically bind functional cis‐regulatory elements encoded upstream of retina‐specific genes. This study presents the first structural analysis of CRX, paving the way for a new approach to studying the biochemistry of this protein and its disease‐causing mutant protein variants.

Human iPSC-Derived Retinal Organoids and Retinal Pigment Epithelium for Novel Intronic RPGR Variant Assessment for Therapy Suitability.

The RPGR gene encodes Retinitis Pigmentosa GTPase Regulator, a known interactor with ciliary proteins, which is involved in maintaining healthy photoreceptor cells. Variants in RPGR are the main contributor to X-linked rod-cone dystrophy (RCD), and RPGR gene therapy approaches are in clinical trials. Hence, elucidation of the pathogenicity of novel RPGR variants is important for a patient therapy opportunity. Here, we describe a novel intronic RPGR variant, c.1415 − 9A>G, in a patient with RCD, which was classified as a variant of uncertain significance according to current clinical diagnostic criteria. The variant lay several base pairs intronic to the canonical splice acceptor site, raising suspicion of an RPGR RNA splicing abnormality and consequent protein dysfunction. To investigate disease causation in an appropriate disease model, induced pluripotent stem cells were generated from patient fibroblasts and differentiated to retinal pigment epithelium (iPSC-RPE) and retinal organoids (iPSC-RO). Abnormal RNA splicing of RPGR was demonstrated in patient fibroblasts, iPSC-RPE and iPSC-ROs, leading to a predicted frameshift and premature stop codon. Decreased RPGR expression was demonstrated in these cell types, with a striking loss of RPGR localization at the ciliary transitional zone, critically in the photoreceptor cilium of the patient iPSC-ROs. Mislocalisation of rhodopsin staining was present in the patient’s iPSC-RO rod photoreceptor cells, along with an abnormality of L/M opsin staining affecting cone photoreceptor cells and increased photoreceptor apoptosis. Additionally, patient iPSC-ROs displayed an increase in F-actin expression that was consistent with an abnormal actin regulation phenotype. Collectively, these studies indicate that the splicing abnormality caused by the c.1415 − 9A>G variant has an impact on RPGR function. This work has enabled the reclassification of this variant to pathogenic, allowing the consideration of patients with this variant having access to gene therapy clinical trials. In addition, we have identified biomarkers of disease suitable for the interrogation of other RPGR variants of uncertain significance.

A Rare Case Report on Bardet-Biedl Syndrome

The Bardet-Biedl Syndrome (BBS) is a rare autosomal recessive disorder that primarily affects children born to consanguineous marriages. Cone-rod dystrophy, polydactyly, obesity, learning difficulties, hypogonadism in males, renal abnormalities, nystagmus, speech disorders, developmental delay, polyuria/polydipsia, ataxia, and poor coordination/clumsiness are all common symptoms of this condition. This syndrome has been related to twenty-one different loci (BBS1-BBS21). BBS is usually not diagnosed until the patient begins to exhibit the visual impairments that are hallmark of rod-cone dystrophy, unless the diagnosis is suspected based on antenatal imaging demonstrating polydactyly and structural kidney abnormalities. The current treatment for Bardet–Biedl syndrome is symptomatic, with a focus on intensive care of diabetes, hypertension, and metabolic syndrome to reduce the secondary effects of these illnesses on susceptible organ systems already compromised by BBS, particularly the eyes and kidneys. The patient was admitted with known complaint of bardet biedl syndrome, chronic kidney disease stage 4, hypothyroidism and with chief complaints of pedal oedema, shortness of breath, decreased urine output, pedal oedema, abdominal distention, facial puffiness. Symptomatic treatment is prescribed along with hemodialysis ( thrice a week).

The Natural History of Leber Congenital Amaurosis and Cone–Rod Dystrophy Associated with Variants in the GUCY2D Gene

To describe the spectrum of Leber congenital amaurosis (LCA) and cone-rod dystrophy (CORD) associated with the GUCY2D gene and to identify potential end points and optimal patient selection for future therapeutic trials. International, multicenter, retrospective cohort study. Eighty-two patients with GUCY2D-associated LCA or CORD from 54 families. Medical records were reviewed for medical history, best-corrected visual acuity (BCVA), ophthalmoscopy, visual fields, full-field electroretinography, and retinal imaging (fundus photography, spectral-domain OCT [SD-OCT], fundus autofluorescence). Age of onset, evolution of BCVA, genotype-phenotype correlations, anatomic characteristics on funduscopy, and multimodal imaging. Fourteen patients with autosomal recessive LCA and 68 with autosomal dominant CORD were included. The median follow-up times were 5.2 years (interquartile range [IQR] 2.6-8.8 years) for LCA and 7.2 years (IQR 2.2-14.2 years) for CORD. Generally, LCA presented in the first year of life. The BCVA in patients with LCA ranged from no light perception to 1.00 logarithm of the minimum angle of resolution (logMAR) and remained relatively stable during follow-up. Imaging for LCA was limited but showed little to no structural degeneration. In patients with CORD, progressive vision loss started around the second decade of life. The BCVA declined annually by 0.022 logMAR (P < 0.001) with no difference between patients with the c.2513G>A and the c.2512C>T GUCY2D variants (P= 0.798). At the age of 40 years, the probability of being blind or severely visually impaired was 32%. The integrity of the ellipsoid zone (EZ) and that of the external limiting membrane (ELM) on SD-OCT correlated significantly with BCVA (Spearman ρ= 0.744, P= 0.001, and ρ= 0.712, P < 0.001, respectively) in those with CORD. Leber congenital amaurosis associated with GUCY2D caused severe congenital visual impairment with relatively intact macular anatomy on funduscopy and available imaging, suggesting long preservation of photoreceptors. Despite large variability, GUCY2D-associated CORD generally presented during adolescence, with a progressive loss of vision, and culminated in severe visual impairment during mid-to-late adulthood. The integrity of the ELM and EZ may be suitable structural end points for therapeutic studies ofGUCY2D-associated CORD.

Genetic characteristics of 234 Italian patients with macular and cone/cone-rod dystrophy

Two-hundred and thirty-four Italian patients with a clinical diagnosis of macular, cone and cone-rod dystrophies (MD, CD, and CRD) were examined using next-generation sequencing (NGS) and gene sequencing panels targeting a specific set of genes, Sanger sequencing and—when necessary—multiplex ligation-dependent probe amplification (MLPA) to diagnose the molecular cause of the aforementioned diseases. When possible, segregation analysis was performed in order to confirm unsolved cases. Each patient’s retinal phenotypic characteristics were determined using focal and full-field ERGs, perimetry, spectral domain optical coherence tomography and fundus autofluorescence. We identified 236 potentially causative variants in 136 patients representing the 58.1% of the total cohort, 43 of which were unpublished. After stratifying the patients according to their clinical suspicion, the diagnostic yield was 62.5% and 53.8% for patients with MD and for those with CD/CRD, respectively. The mode of inheritance of all cases confirmed by genetic analysis was 70% autosomal recessive, 26% dominant, and 4% X-linked. The main cause (59%) of both MD and CD/CRD cases was the presence of variants in the ABCA4 gene, followed by variants in PRPH2 (9%) and BEST1 (6%). A careful morpho-functional evaluation of the phenotype, together with genetic counselling, resulted in an acceptable diagnostic yield in a large cohort of Italian patients. Our study emphasizes the role of targeted NGS to diagnose MDs, CDs, and CRDs, as well as the clinical usefulness of segregation analysis for patients with unsolved diagnosis.