Unusual manifestations of x-linked retinoschisis: clinical profile and diagnostic evaluation

Clinical and genetic features of retinoschisis in 120 families with RS1 mutations

BACKGROUND/AIMS

X-linked retinoschisis (XLRS), associated with RS1, is the most common type of X-linked retinopathy in children. This study aimed to identify clinical and genetic features of retinoschisis in 120 families with RS1 variants in China.

METHODS

RS1 variants were collected from our in-house exome data and were predicted by multiple-step bioinformatics analysis. Clinical data of 122 patients from 120 families with potential pathogenic RS1 variants were analysed and summarised, respectively.

RESULT

Totally, 79 hemizygous variants (53 missense, 25 truncation and 1 indel), were detected. All except one (78/79, 98.7%), including 22 novels, were classified as potential pathogenic and detected exclusively in 120 families with retinoschisis. Clinical data demonstrated an average age of presentation at 5 years (1 month-41 years). Macular changes were classified as macular schisis (87.5%), macular atrophy (10.7%), normal (0.9%) and unclassified (0.9%). Patients with macular atrophy had older age but similar visual acuity compared with macular schisis. Peripheral retinal changes included flat retinoschisis (52.4%), bullous retinoschisis (BRS) (10.7%) and normal-like (36.9%) patients. Spontaneous regression was observed in two patients with BRS on follow-up examination. Visual acuity in the peripheral retinoschisis group was worse than that without peripheral retinoschisis.

CONCLUSION

Almost all rare RS1 variants were potential pathogenic. All patients with RS1 pathogenic variants showed detectable characteristics in the macula and/or peripheral retina. Our data on RS1 variants and associated clinical phenotypes may be of value for clinical diagnosis and genetic test of retinoschisis.

X-linked retinoschisis: mutation spectrum and genotype-phenotype relationship in an Italian pediatric cohort

BACKGROUND

X-linked juvenile retinoschisis (×LRS) is an X-linked vitreoretinal degenerative disease that consists of variable phenotypes ranging from severe early-onset defects to subtle abnormalities diagnosed in elderly patients. XLRS is caused by a loss of function of the protein Retinoschisin (RS1), which is essential to preserve retinal integrity and function of photoreceptor-bipolar synapse. The literature data so far mostly agree on the absence of a clear genotype-phenotype correlation in XLRS. We reviewed clinical and molecular characteristics of a cohort of Italian pediatric XLRS patients to assess the presence of a correlation between genotype and phenotype severity.

MATERIALS AND METHODS

We retrospectively examined clinical and genetic features of a cohort of 27 XLRS patients. In this study we included patients with a diagnosis of XLRS confirmed by fundus photography, spectral domain optical coherence tomography, and molecular analysis and with an onset of less than 10 years of age. We sorted RS1 variants according to their effect of RS1 structure and function in three separate groups.

RESULTS

According to previous studies, we did not observe a conclusive genotype-phenotype correlation in our cohort; nevertheless, we noticed that patients harboring RS1 variants leading to RS1-secreted mutants show a more homogeneous phenotype, with an overall good visual acuity, compared to the other two groups.

CONCLUSIONS

Our data support the hypothesis that secretion profile of RS1 could influence the severity of the phenotype. More extensive and functional studies are needed to acquire notions in view of the opportunity of gene replacement therapy for XLRS patients.

Typical and atypical clinical presentations of X-Linked retinoschisis: A case series and literature review

X-linked retinoschisis (XLRS) is an X-linked inherited retinal dystrophy characterized by mild-to-severe visual impairment, splitting of the retinal layers, and a reduction in the dark-adapted b-wave amplitude on the electroretinogram. Typical clinical features include macular and peripheral schisis. Relatively common features reported include rhegmatogenous or tractional retinal detachment, vitreous hemorrhage, retinal pigment epithelial changes, vitreous veils, and various retinal vascular abnormalities with or without exudation. Macular hole and macular folds are atypical presentations of XLRS, along with several other rare findings. Here, we report 4 cases of XLRS with atypical clinical presentations and review the literature on XLRS, with a focus on the variable clinical features of this condition.

Retinal vasoproliferative tumor as first sign of X-linked retinoschisis in a 12-month-old boy

X-linked retinoschisis (XLRS) has been associated with retinal vascular abnormalities, but retinal vasoproliferative tumor (RVPT) has been rarely reported in this context. We describe the case of a 12-month-old boy presenting with esotropia of his left eye due to extensive exudation secondary to RVPT. Right eye examination revealed macular and bullous peripheral retinoschisis. Combining laser photocoagulation and intravitreal injections of anti-vascular endothelial growth factor allowed control of the exudative process at 12 months follow-up. RVPT could be the first sign of XLRS.

Rare eye diseases in India: A concise review of genes and genetics

Rare eye diseases (REDs) are mostly progressive and are the leading cause of irreversible blindness. The disease onset can vary from early childhood to late adulthood. A high rate of consanguinity contributes to India’s predisposition to RED. Most gene variations causing REDs are monogenic and, in some cases, digenic. All three types of Mendelian inheritance have been reported in REDs. Some of the REDs are related to systemic illness with variable phenotypes in affected family members. Approximately, 50% of the children affected by REDs show associated phenotypes at the early stages of the disease. A precise clinical diagnosis becomes challenging due to high clinical and genetic heterogeneity. Technological advances, such as next-generation sequencing (NGS), have improved genetic and genomic testing for REDs, thereby aiding in determining the underlying causative gene variants. It is noteworthy that genetic testing together with genetic counseling facilitates a more personalized approach in the accurate diagnosis and management of the disease. In this review, we discuss REDs identified in the Indian population and their underlying genetic etiology.

Phenotypic characterization of X-linked retinoschisis: Clinical, electroretinography, and optical coherence tomography variables

Aims:

To study the phenotypic characteristics of X-linked retinoschisis (XLRS) and report the clinical, electroretinogram (ERG), and optical coherence tomography (OCT) variables in Indian eyes.

Design:

A retrospective study.

Materials and Methods:

Medical records of 21 patients with retinoschisis who were genetically confirmed to have RS1 mutation were reviewed. The phenotype characterization included the age of onset, best-corrected visual acuity, refractive error, fundus findings, OCT, and ERG.

Statistical Analysis Used:

Data from both the eyes were used for analysis. A P < 0.05 was set as statistical significance. Data were not normally distributed (P < 0.05, Shapiro wilk); hence, nonparametric tests were used for statistical analysis.

Results:

All were males whose mean age of presentation was 9 years. Visual acuity was moderately impaired (median 0.6 logMAR, interquartile range: 0.47, 1) in these eyes with a hyperopic refractive error of median +1.75 Ds (interquartile range: +0.50 Ds, +4.25 Ds). About 54.7% of the eyes had both foveal and peripheral schisis, isolated foveal schisis was seen in 28.5% of the eyes, and schisis with retinal detachment was seen in 16.6% of the eyes. The inner nuclear layer was found to be commonly involved in the schisis, followed by outer nuclear and plexiform layers as evident on OCT. On ERG, a- and b-wave amplitudes were significantly reduced in eyes with foveal and peripheral schisis when compared to the eyes with only foveal schisis (P < 0.05).

Conclusions:

XLRS has phenotypic heterogeneity as evident on OCT, ERG, and clinical findings.

Genetic analysis and clinical features of X-linked retinoschisis in Chinese patients

Many mutations in the retinoschisis (RS1) gene have been identified, but there are limited clinical data relating to the different genotypes. This study investigated the genotype, clinical phenotype and therapies for X-linked juvenile retinoschisis (XLRS) patients in China to evaluate the effects of gene mutations and therapies on the prognosis of the disease. Thirty patients were recruited in the study. Genetic examination identified 8 novel RS1 gene mutations. Twenty-four patients were identified as missense mutation, which was the most common gene mutation in XLRS patients. Amino acids 102 and 209 were the most common mutation areas, accounting for a total 35.7% of all patients. Mutations affecting amino acid 102 were associated with poor results on the flash electroretinogram (ERG). Sixteen patients had various complications. Anti-vascular endothelial growth factor (VEGF) drugs were given to four patients with hemorrhage or other complications, and serious adverse events did not occur. Our outcome demonstrates that missense mutation was the leading cause of XLRS and more than half of the patients with this missense had various complications. Anti-VEGF drugs may be an effective and safe way to prevent deterioration of XLRS with certain complications. There is wide genotypic and phenotypic variability in Chinese patients with XLRS.

Retinal Diseases Caused by Mutations in Genes Not Specifically Associated with the Clinical Diagnosis

Purpose

When seeking a confirmed molecular diagnosis in the research setting, patients with one descriptive diagnosis of retinal disease could carry pathogenic variants in genes not specifically associated with that description. However, this event has not been evaluated systematically in clinical diagnostic laboratories that validate fully all target genes to minimize false negatives/positives.

Methods

We performed targeted next-generation sequencing analysis on 207 ocular disease-related genes for 42 patients whose DNA had been tested negative for disease-specific panels of genes known to be associated with retinitis pigmentosa, Leber congenital amaurosis, or exudative vitreoretinopathy.

Results

Pathogenic variants, including single nucleotide variations and copy number variations, were identified in 9 patients, including 6 with variants in syndromic retinal disease genes and 3 whose molecular diagnosis could not be distinguished easily from their submitted clinical diagnosis, accounting for 21% (9/42) of the unsolved cases.

Conclusion

Our study underscores the clinical and genetic heterogeneity of retinal disorders and provides valuable reference to estimate the fraction of clinical samples whose retinal disorders could be explained by genes not specifically associated with the corresponding clinical diagnosis. Our data suggest that sequencing a larger set of retinal disorder related genes can increase the molecular diagnostic yield, especially for clinically hard-to-distinguish cases.

X-Linked Retinoschisis: Phenotypic Variability in a Chinese Family

X-linked juvenile retinoschisis (XLRS), a leading cause of juvenile macular degeneration, is characterized by a spoke-wheel pattern in the macular region of the retina and splitting of the neurosensory retina. Our study is to describe the clinical characteristics of a four generations of this family (a total of 18 members)with X-linked retinoschisis (XLRS) and detected a novel mutations of c.3G > A (p.M1?) in the initiation codon of the RS1 gene. by direct sequencing.Identification of this mutation in this family provides evidence about potential genetic or environmental factors on its phenotypic variance, as patients presented with different phenotypes regardless of having the same mutation. Importantly, OCT has proven vital for XLRS diagnosis in children.

Long-term outcomes of vitrectomy for progressive X-linked retinoschisis

PURPOSE

To evaluate the long-term outcomes of vitrectomy for progressive X-linked retinoschisis.

DESIGN

Prospective, nonrandomized, consecutive, interventional case series.

METHODS

Twenty-eight eyes of 22 patients who were diagnosed with progressive X-linked retinoschisis were divided into 2 groups: a nonsurgical group (n = 11) and a vitrectomy group (n = 17). The main outcome measures included best-corrected visual acuity, the area of the macular schisis cavity measured by optical coherence tomography, the retinal anatomic status, and complications.

RESULTS

The mean follow-up period was 34.7 months (range, 10 to 68 months). The mean best-corrected visual acuity increased from 20/125 at baseline to 20/55 at the final follow-up in the vitrectomy group (P = .001), but decreased from 20/100 at baseline to 20/400 at the final follow-up in the nonsurgical group (P = .000). In the vitrectomy group, the macular schisis cavity resolved in all 17 eyes; the mean area of the macular schisis cavity decreased from 0.85 mm(2) at baseline to 0.23 mm(2) at the final follow-up (P = .000), and the retinas of 16 eyes (94%) were attached after surgery. In the nonsurgical group, retinal schisis progressively extended in 9 eyes (82%); the mean area of the macular schisis cavity increased from 0.82 mm(2) at baseline to 1.21 mm(2) at the final follow-up (P = .000); in 8 eyes (72%), retinal detachment developed, and 2 eyes (18%) experienced vitreous hemorrhage, which terminated the observations.

CONCLUSIONS

Vitrectomy may be an effective and essential treatment for patients with progressive X-linked retinoschisis to prevent a deterioration of vision before severe complications developed in their eyes.

X-linked juvenile retinoschisis: clinical diagnosis, genetic analysis, and molecular mechanisms

X-linked juvenile retinoschisis (XLRS, MIM 312700) is a common early onset macular degeneration in males characterized by mild to severe loss in visual acuity, splitting of retinal layers, and a reduction in the b-wave of the electroretinogram (ERG). The RS1 gene (MIM 300839) associated with the disease encodes retinoschisin, a 224 amino acid protein containing a discoidin domain as the major structural unit, an N-terminal cleavable signal sequence, and regions responsible for subunit oligomerization. Retinoschisin is secreted from retinal cells as a disulphide-linked homo-octameric complex which binds to the surface of photoreceptors and bipolar cells to help maintain the integrity of the retina. Over 190 disease-causing mutations in the RS1 gene are known with most mutations occurring as non-synonymous changes in the discoidin domain. Cell expression studies have shown that disease-associated missense mutations in the discoidin domain cause severe protein misfolding and retention in the endoplasmic reticulum, mutations in the signal sequence result in aberrant protein synthesis, and mutations in regions flanking the discoidin domain cause defective disulphide-linked subunit assembly, all of which produce a non-functional protein. Knockout mice deficient in retinoschisin have been generated and shown to display most of the characteristic features found in XLRS patients. Recombinant adeno-associated virus (rAAV) mediated delivery of the normal RS1 gene to the retina of young knockout mice result in long-term retinoschisin expression and rescue of retinal structure and function providing a 'proof of concept' that gene therapy may be an effective treatment for XLRS.

Novel RS1 mutations associated with X-linked juvenile retinoschisis

To identify mutations in the retinoschisin (RS1) gene in families with X-linked retinoschisis (XLRS). Twenty families with XLRS were enrolled in this study. All six coding exons and adjacent intronic regions of RS1 were amplified by polymerase chain reaction (PCR). The nucleotide sequences of the amplicons were determined by Sanger sequencing. Ten hemizygous mutations in RS1 were detected in patients from 14 of the 20 families. Four of the ten mutations were novel, including c:176G>A (p:Cys59Tyr) in exon 3, c:531T>G (p:Tyr177X), c:607C>G (p:Pro203Ala) and c:668G>A (p:Cys223Tyr) in exon 6. These four novel mutations were not present in 176 normal individuals. The remaining six were recurrent mutations, including c:214G>A (p:Glu72Lys), c:304C>T (p:Arg102Trp), c:436G>A (p:Glu146Lys), c:544C>T (p:Arg182Cys), c:599G>A (p:Arg200His) and c:644A>T (p:Glu215Val). Our study expanded the mutation spectrum of RS1 and enriches our understanding of the molecular basis of XLRS.

[X linked retinoschisis, unusual presentation: strabismus]

CASE REPORT

X linked retinoschisis is a recessively inherited degenerative retinopathy. We report two cases that debuted with an unusual presentation (strabismus) in early childhood (months). Both of them presented with vitreous veils in the retinal periphery. Mutation in the XLRS1 gene was detected in both cases.

DISCUSSION

X linked retinoschisis is one of the leading causes of macular degeneration in male children. Clinical features include a stellate foveal schisis, with or without peripheral retinoschisis. Clinical diagnosis is often difficult because of a high degree of phenotype variability. Furthermore, ERG and OCT may be normal in early stages of the disease. In our opinion, the XLRS1 gene mutation screening provides a powerful clinical tool for evaluating clinically ambiguous cases of X linked retinoschisis.

Hereditary retinal disease

PURPOSE OF REVIEW

This article reports recent advances in the diagnosis, genetic analysis, and treatment of hereditary retinal disease.

RECENT FINDINGS

Clinicians and scientists continue to reveal the relationship between phenotype and genotype in hereditary retinal diseases. Persistent investigation and progressive technology are advancing the efficiency of mutation discovery. This technology is also leading to readily available genetic testing that aids clinicians in the diagnosis of these diseases. Functional genetic studies, and laboratory and human clinical trials are occurring that may lead to future treatment of these disorders.

SUMMARY

A literature review of the recent discoveries and potential treatments for retinitis pigmentosa, Leber's congenital amaurosis, X-linked retinoschisis, Best's disease, Stargardt's disease, and congenital stationary night blindness is presented, along with a guide for clinicians seeking genetic testing of patients.