ABSTRACT Introduction Inherited retinal diseases (IRDs) are clinically and genetically diverse conditions whose heterogeneity makes molecular diagnosis challenging. These challenges can lead to interpretation discordance which has a particular impact on gene-targeted therapies for IRD. Methods Discordance was evaluated in a clinical testing cohort and in ClinVar. 140 sequence variants identified through genetic testing in a cohort of pediatric participations with IRD were reclassified using the American College of Medical Genetics and Genomics (ACMG) and Association for Molecular Pathology (AMP) guidelines for variant interpretation. ClinVar datasets from December 2, 2019 and January 3, 2022 for the gene RPE65 were analyzed for discordance. Results The discordance rate in the pediatric cohort was 22.2%. Discordance in ClinVar increased from 23.6% to 36.6%. Discussion Discordance in the pediatric cohort may have been impacted by subjective application of the ACMG/AMP guidelines and heterogeneity in IRD. Subjectivity in the guidelines, laboratory differences, and lack of interpretation review may have contributed to discordance in ClinVar. Work to improve interpretation for IRD should include better understanding of the genetic influences of IRD and optimization of the ACMG/AMP guidelines for this field.

ABSTRACT Purpose Clinical variability and incomplete penetrance characterize retinal dystrophies associated with PRPH2 gene variants. Here, we utilized adaptive nanopore long-read sequencing (LRS) to solve a genetic diagnosis for dominantly inherited macular dystrophies in two families. Methods Patient 1 (P1) and her daughter, Patient 2 (P2) were clinically evaluated using multimodal imaging and electrophysiological testing at Helsinki University Hospital, Finland, and Patient 3 (P3) from a different family, at Loma Linda University, USA. The patients were subjected to retinal dystrophy gene panels and the suspected duplications were characterized with nanopore LRS. Results P1 presented with butterfly-shaped pattern dystrophy (BPD) and P2 with vitelliform macular dystrophy. P3 showed BPD in the right eye and late-stage BPD in the left. Gene panels suggested that the patients shared the same heterozygous 482 bp PRPH2 exon 2 duplication. LRS revealed the duplications to be almost 4kb in size with breakpoints (BP) in intronic Alu-elements. In P1 and P2, the 3'BP resides within a novel Alu-element. The duplication has not been reported earlier and is missing from the gnomAD database. Conclusion This study presents novel PRPH2 exon 2 duplications associated with macular dystrophies.

ABSTRACT Background Oguchi disease, a rare form of congenital stationary night blindness (CSNB), is an autosomal recessive inherited retinal disorder (IRD) caused by pathogenic variants in the SAG gene, which encodes arrestin-1, a key protein in the phototransduction cascade. Materials and methods We present a case of a 35-year-old male with nyctalopia, progressive central vision loss, and refractory CME. Case presentation A 35-year-old male presented with nyctalopia and progressive central vision loss. Evaluation revealed attenuated retinal vessels, peripheral pigmentary changes, and severe CME bilaterally. Despite treatment with carbonic anhydrase inhibitors and NSAIDS, CME persisted. Initial genetic testing identified a heterozygous pathogenic SAG variant (p.Arg193*), raising suspicion for autosomal dominant RP. However, advanced long-read sequencing revealed a second pathogenic intronic SAG variant (c.-29+3A>G) in trans with the initial variant, confirming a diagnosis of autosomal recessive Oguchi disease.

ABSTRACT Introduction Pathogenic variants in TUBB4B, which encodes the β-tubulin 4B isotype of microtubule subunits, have been associated with Leber congenital amaurosis with early-onset deafness (LCAEOD), an autosomal dominant condition characterized by early and severe loss of photoreceptor and cochlear cells. The majority of reported cases feature early disease onset and are caused by missense mutations in the R390/R391 hotspot. Methods Multimodal evaluation included ultra-widefield pseudocolor and autofluorescence fundus photography, spectral-domain optical coherence tomography, full-field electroretinography, Goldmann kinetic perimetry, audiography, and genetic testing with next-generation sequencing. Results We report seven individuals from three unrelated families affected by cone-rod dystrophy and sensorineural hearing loss associated with a novel variant in TUBB4B (c.784C > T, p.R262W). Cone-rod dystrophy associated with this variant generally features a later age of onset compared to the Leber congenital amaurosis caused by variants in the canonical hotspot. Discussion This report expands the mutation spectrum and phenotypic range of TUBB4B-associated retinopathies beyond the R390/R391 hotspot and may offer insight into the pathogenesis of this rare tubulinopathy.

ABSTRACT Purpose To assess the ocular characteristics, retinal microvasculature, and long-term outcomes of patients with nanophthalmos associated with mutations in the membrane frizzled-related protein (MFRP) gene, and to compare these findings with those observed in nanophthalmos cases without MFRP gene mutations. Methods In this retrospective cohort study, patients with MFRP-associated nanophthalmos and those with nanophthalmos without MFRP gene mutations were included. Best-corrected visual acuity (BCVA), spherical equivalent (SE), axial length (AL), optical coherence tomography (OCT), and OCT angiography parameters—including vascular density (VD) and foveal avascular zone (FAZ) measurements in the superficial capillary plexus (SCP), deep capillary plexus (DCP), and choriocapillaris (CC)—were evaluated at presentation and at the 5th-year follow-up. Results At presentation and 5-year follow-up, patients with MFRP-associated nanophthalmos exhibited significantly shorter AL and higher SE compared to those without MFRP mutations (all p < 0.001). Central macular thickness (CMT), subfoveal choroidal thickness (SFCT), and retinal nerve fiber layer (RNFL) thickness were significantly greater in the MFRP-associated group at presentation and 5-year follow-up (all p < 0.05). OCT angiography revealed reduced parafoveal VD in the SCP and DCP, as well as decreased foveal and parafoveal VD in the CC in the MFRP group compared to the group without MFRP mutations (all p < 0.05). FAZ areas in the SCP and DCP were also significantly smaller in the MFRP group (p < 0.001 and p = 0.01, respectively). Conclusions Eyes with MFRP-associated nanophthalmos exhibit significantly higher SE, shorter AL, and more pronounced alterations in retinal structure and microvasculature compared with eyes without MFRP mutations.

ABSTRACT Background Vascular endothelial growth factor (VEGF) is an angiogenic factor that contributes to the vascular permeability and neovascularization. This study aims to investigate whether the polymorphisms of the VEGF gene at the −2578C/A (rs699947) and −634 G/C (rs2010963) are risk factors for diabetic retinopathy (DR) in Thai patients with type 2 diabetes. Methods We conducted a case-control study. Thai patients with type 2 diabetes were enrolled in the study and assigned to a diabetic with retinopathy (DR) or a diabetic without retinopathy (DWR) group based on the grading of retina images. Polymerase chain reaction—restriction fragment length polymorphism (PCR-RFLP) was used to determine polymorphisms of the VEGF gene at the −2578C/A and −634 G/C loci. Results A total of 85 patients, including 37 with DR and 48 without DR, were enrolled in this study. We found that the genotype distributions and allele frequencies for the VEGF-2578C/A (rs699947) and VEGF-634 G/C (rs2010963) polymorphisms did not differ between the patients with DR and those without DR. Neither polymorphism was significantly associated with DR development. Conclusions Our data suggest that VEGF-2578C/A (rs699947) and VEGF-634 G/C (rs2010963) polymorphisms may not be the risk factors for DR in Thai patients with type 2 diabetes mellitus.

ABSTRACT Introduction Loeys-Dietz syndrome (LDS) is a rare autosomal dominant connective tissue disorder most commonly due to pathogenic variants in the transforming growth factor beta receptor genes TGFBR1 and TGFBR2. There have been reports of a few sporadic cases of LDS patients exhibiting a vitreoretinopathy phenotype due to pathogenic variants in the TGFBR2 gene. Case Presentation We report a 13-year-old female with LDS who harbored a de novo pathogenic missense variant (c.1582C>T, p.Arg528Cys) in TGFBR2. She presented with reduced visual acuity in the right eye due to a vitreous hemorrhage. Fluorescein angiography identified neovascularization in the right eye with peripheral avascular retina in both eyes. These phenotypic features were similar to those seen in familial exudative vitreoretinopathy (FEVR). Intravitreal anti-VEGF treatment in the right eye led to visual improvement, followed by laser photocoagulation of the peripheral retina of both eyes to mitigate future complications. Discussion This is the second reported case of a missense variant at the amino acid residue 528 (Arg528) of TGFBR2 that results in a FEVR-like phenotype in a LDS patient. In silico protein prediction and machine learning analyses of the affected region of the TGFBR2 protein suggest this missense variant disrupts the protein kinase domain. We hypothesize this change influences the Wnt/beta-catenin pathway, leading to abnormal retinal vasculogenesis. Conclusions This case highlights the importance of a genotype to phenotype relationship in LDS and suggests that certain variants in TGFBR2 may predispose to vitreoretinopathy. Recognition of this is important as timely anti-VEGF and laser intervention can limit visual threatening complications.

ABSTRACT Introduction We report the case of a 42-year-old Venezuelan woman with childhood-onset autosomal recessive retinitis pigmentosa type 90 (RP90), presenting an unusual and distinctive clinical phenotype characterized by macular pseudocoloboma, very early-onset acquired color vision disorder progressing to severe functional dyschromatopsia, and early-onset severe posterior subcapsular cataracts. Her affected brother exhibited a similar phenotype, while her parents and the other two siblings remained unaffected. Methods and Results Massive parallel sequencing identified two novel IDH3A variants: c.127G>T (chr15:78449926 G>T; no dbSNP entry) and c.419T>C (chr15:78454052T>C; no dbSNP entry), in compound heterozygosity and confirmed to be in trans location. Both missense variants, absent from population databases, were predicted to be deleterious by multiple in silico tools and are located in critical domains involved in enzymatic complex stability, catalytic activity and subunit interactions. Conclusions This case reinforces the association between IDH3A mutations and RP90, corroborates key phenotypic features described in limited published reports—the presence of macular pseudocoloboma—and expands the mutational spectrum of the gene. Moreover, it highlights the role of mitochondrial metabolism in photoreceptor degeneration and proposes a link between them. Our findings underscore the need for functional studies to elucidate the pathogenic mechanisms underlying IDH3A-related retinopathies.

ABSTRACT Background Poland Syndrome is primarily characterized by musculoskeletal anomalies, such as unilateral absence of the sternocostal head of the pectoralis major. Ocular associations with Poland syndrome are rare, and ADAMTSL4 mutations, typically linked to autosomal recessive ectopia lentis, have not been previously associated with this condition. Case We describe a 20-month-old female with left-sided Poland syndrome who presented with intermittent right eye pain and a history of progressive corneal clouding. Examination revealed bilateral ectopia lentis, buphthalmos, and elevated intraocular pressure. Genetic testing identified a homozygous ADAMTSL4 variant (c.767_786del20), a novel association with Poland syndrome. The patient underwent successful bilateral lensectomy and anterior vitrectomy, and management of glaucoma was initiated. Her monochorionic diamniotic (MCDA) twin, also harboring the same ADAMTSL4 mutation, exhibited bilateral ectopia lentis and underwent surgical intervention. Discussion This report is the first to document an association between Poland syndrome and an ADAMTSL4 mutation, potentially suggesting a shared underlying defect in microfibril assembly. These findings expand our understanding of the genetic and developmental complexities of Poland syndrome and underscore the importance of early ophthalmological evaluation in such patients. Conclusion This case highlights the significance of genetic and ocular investigations in Poland syndrome, contributing to knowledge on its broader phenotypic spectrum and potential genetic etiologies. Further research is warranted to elucidate the role of ADAMTSL4 in microfibril-related anomalies.

ABSTRACT Background Retinoblastoma is the most common intraocular tumor of childhood. In Lebanon, its incidence is reported at 3.6 per million person-years. This study aimed to characterize the spectrum of RB1 variants in hereditary retinoblastoma and explore genotype-phenotype associations in a Lebanese cohort. Methods A retrospective chart review was conducted on retinoblastoma patients enrolled in the Children’s Cancer Institute at the American University of Beirut Medical Center from 2012 to 2022. Genetic data (RB1 sequencing and karyotype), clinical characteristics, imaging, treatment, and outcomes were collected and compared between hereditary and sporadic cases, and across different variant types. Results A total of 47 patients underwent genetic testing; 63% had hereditary retinoblastoma with 23 patients carrying single nucleotide changes, including four novel mutations, 3 patients with submicroscopic deletions/duplications, and 3 with deletion 13q syndrome. Nonsense mutations were most frequent (52.2%), followed by frameshift and splice-site alterations. Bilaterality was significantly associated with hereditary disease (85.7% vs. 21.1%, p < 0.001), and more common among Syrian patients (p = 0.04). Median age at diagnosis was younger in the hereditary group, although not statistically significant. Enucleation rates (57.1% vs. 78.9%) and vision outcomes were similar across groups (p > 0.05). No significant differences in treatment outcomes were found among different variant types. Among the 3 patients with deletion 13q, two exhibited severe psychomotor and developmental delays. Conclusion Hereditary retinoblastoma accounted for 63% of cases, with 23 pathogenic variants including four novel ones. Bilaterality and Syrian nationality were significantly associated with RB1 positivity. This study underscores the importance of comprehensive RB1 genetic testing in improving diagnostic accuracy, guiding treatment decisions, and supporting genetic counselling, particularly in non-Western populations.