X-LINKED JUVENILE RETINOSCHISIS IN A CONSANGUINEOUS FAMILY: Phenotypic Variability and Report of a Homozygous Female Patient

A Carrier Female Manifesting an Unusual X-Linked Retinoschisis Phenotype Associated with the Pathogenic Variant c.266delA, p.(Tyr89LeufsTer37) in RS1, and Skewed X-Inactivation

X-linked retinoschisis (XLRS) is the most common juvenile macular degeneration in males. Unlike most other X-linked retinal dystrophies, carrier heterozygous females are very rarely reported to show clinical features of the disease. Herein, we describe unusual retinal features in a 2-year-old female infant with family history and genetic testing consistent with XLRS.

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.

Clinical and genetic study of a pseudo-dominant retinoschisis pedigree: the first female patient reported in Chinese population

BACKGROUND

The inheritance pattern of genetically confirmed hereditary juvenile retinoschisis reported so far is X-linked recessive with limited number of female cases. We identified a female patient with retinoschisis, and this study reports the clinical features as well as the underlying genetic defect of this family.

MATERIALS AND METHODS

Detailed family history and pedigree analysis were performed. All affected subjects underwent detailed ophthalmic examinations, including best corrected visual acuity (BCVA), dilated fundoscopy, optical coherent tomography (OCT) and fundus autofluorescence (FAF). DNA sample of the proband was sequenced by next-generation sequencing (NGS). Sanger sequencing was performed for validation and segregation.

RESULTS

Three affected subjects including one female and two males were confirmed in this consanguineous family. The BCVA ranged from 20/50 to hand motion. Foveoschisis, hyperopia, subcapsular cataracts, vitreous opacity, retinal pigmentation, and macular atrophy were present in all three patients, with variable severity. Nystagmus, esotropia, and retinal vessels transposition were noted in the female patient. Retinal detachment occurred in the female patient and her affected brother. A small deletion in RS1 gene c.97delT (p.W33Gfs*93) (NM_000330.3) was found, which was co-segregated in the pedigree.

CONCLUSIONS

Consanguineous family having XLRS female patient could manifest as pseudo-dominant inheritance. Significant intrafamilial phenotypic variation was revealed.

Stellate nonhereditary idiopathic foveomacular retinoschisis resolution after vitreomacular adhesion release

PURPOSE

To present a case of stellate nonhereditary idiopathic foveomacular retinoschisis (SNIFR) resolution associated with vitreomacular adherence (VMA) release and propose a potential contributing association between SNIFR and vitreomacular interactions.

OBSERVATIONS

A 67-year-old female patient was diagnosed and followed for SNIFR in OD with spectral-domain optical coherence tomography (SD-OCT) scans at presentation and subsequent visits at 3, 6, 16 and 22 months. VMA and foveomacular retinoschisis remained unchanged on SD-OCT during the first 6 months of the follow-up. At 16-month follow-up visit, SD-OCT revealed VMA release and an important improvement of the macular schisis. At 22 months of follow-up, SNIFR cavities completely resolved in the presence of posterior hyaloid separation from the macular area without any adjunct treatment. The authors could not identify any other possible cause to justify the resolution of SNIFR other than VMA release in this case. Patient did not undergo any treatment for OD other than phacoemulsification 3 months after initial visit.

CONCLUSION

The present case illustrates with SD-OCT scans a possible association between SNIFR resolution and VMA release, highlighting a potential tractional component of the posterior vitreous on the internal limiting membrane and consequent glial cells stretching with schisis formation.

Of men and mice: Human X-linked retinoschisis and fidelity in mouse modeling

X-linked Retinoschisis (XLRS) is an early-onset transretinal dystrophy, often with a prominent macular component, that affects males and generally spares heterozygous females because of X-linked recessive inheritance. It results from loss-of-function RS1 gene mutations on the X-chromosome. XLRS causes bilateral reduced acuities from young age, and on clinical exam and by ocular coherence tomography (OCT) the neurosensory retina shows foveo-macular cystic schisis cavities in the outer plexiform (OPL) and inner nuclear layers (INL). XLRS manifests between infancy and school-age with variable phenotypic presentation and without reliable genotype-phenotype correlations. INL disorganization disrupts synaptic signal transmission from photoreceptors to ON-bipolar cells, and this reduces the electroretinogram (ERG) bipolar b-wave disproportionately to photoreceptor a-wave changes. RS1 gene expression is localized mainly to photoreceptors and INL bipolar neurons, and RS1 protein is thought to play a critical cell adhesion role during normal retinal development and later for maintenance of retinal structure. Several independent XLRS mouse models with mutant RS1 were created that recapitulate features of human XLRS disease, with OPL-INL schisis cavities, early onset and variable phenotype across mutant models, and reduced ERG b-wave to a-wave amplitude ratio. The faithful phenotype of the XLRS mouse has assisted in delineating the disease pathophysiology. Delivery to XLRS mouse retina of an AAV8-RS1 construct under control of the RS1 promoter restores the retinal structure and synaptic function (with increase of b-wave amplitude). It also ameliorates the schisis-induced inflammatory microglia phenotype toward a state of immune quiescence. The results imply that XLRS gene therapy could yield therapeutic benefit to preserve morphological and functional retina particularly when intervention is conducted at earlier ages before retinal degeneration becomes irreversible. A phase I/IIa single-center, open-label, three-dose-escalation clinical trial reported a suitable safety and tolerability profile of intravitreally administered AAV8-RS1 gene replacement therapy for XLRS participants. Dose-related ocular inflammation occurred after dosing, but this resolved with topical and oral corticosteroids. Systemic antibodies against AAV8 increased in dose-dependent fashion, but no antibodies were observed against the RS1 protein. Retinal cavities closed transiently in one participant. Technological innovations in methods of gene delivery and strategies to further reduce immune responses are expected to enhance the therapeutic efficacy of the vector and ultimate success of a gene therapy approach.

X-Linked Retinoschisis in Females in a Consanguineous Family: A Rare Entity

X-linked juvenile retinoschisis (XLRS) is a disease considered characteristic for males. In this study we report a consanguineous family in which 3 daughters were diagnosed with XLRS. Typical signs of XLRS were detected in 2 girls, aged 4 and 15. Fundoscopic examination of the father and the oldest daughter (age 17) revealed bilateral atrophic macula and retinal thinning. Although rare and considered characteristic for males, XLRS can be seen in females in Middle-East countries that have a high rate of consanguineous marriage. It can be overlooked by ophthalmologists and these patients may be misdiagnosed.

The X-linked retinopathies: Physiological insights, pathogenic mechanisms, phenotypic features and novel therapies

X-linked retinopathies represent a significant proportion of monogenic retinal disease. They include progressive and stationary conditions, with and without syndromic features. Many are X-linked recessive, but several exhibit a phenotype in female carriers, which can help establish diagnosis and yield insights into disease mechanisms. The presence of affected carriers can misleadingly suggest autosomal dominant inheritance. Some disorders (such as RPGR-associated retinopathy) show diverse phenotypes from variants in the same gene and also highlight limitations of current genetic sequencing methods. X-linked disease frequently arises from loss of function, implying potential for benefit from gene replacement strategies. We review X-inactivation and X-linked inheritance, and explore burden of disease attributable to X-linked genes in our clinically and genetically characterised retinal disease cohort, finding correlation between gene transcript length and numbers of families. We list relevant genes and discuss key clinical features, disease mechanisms, carrier phenotypes and novel experimental therapies. We consider in detail the following: RPGR (associated with retinitis pigmentosa, cone and cone-rod dystrophy), RP2 (retinitis pigmentosa), CHM (choroideremia), RS1 (X-linked retinoschisis), NYX (complete congenital stationary night blindness (CSNB)), CACNA1F (incomplete CSNB), OPN1LW/OPN1MW (blue cone monochromacy, Bornholm eye disease, cone dystrophy), GPR143 (ocular albinism), COL4A5 (Alport syndrome), and NDP (Norrie disease and X-linked familial exudative vitreoretinopathy (FEVR)). We use a recently published transcriptome analysis to explore expression by cell-type and discuss insights from electrophysiology. In the final section, we present an algorithm for genes to consider in diagnosing males with non-syndromic X-linked retinopathy, summarise current experimental therapeutic approaches, and consider questions for future research.

STELLATE NONHEREDITARY IDIOPATHIC FOVEOMACULAR RETINOSCHISIS ACCOMPANIED BY CONTRALATERAL PERIPHERAL RETINOSCHISIS

PURPOSE

To present a patient with stellate nonhereditary idiopathic foveomacular retinoschisis on one eye and peripheral retinoschisis without foveal affection on the other eye.

METHODS

A case report with complete workup of family history and clinical examination, including multimodal imaging with optical coherence tomography and angiography, fluorescein angiography, and infrared fundus imaging. Genetic testing for gene mutation XRLS1 was performed.

RESULTS

A white woman with unremarkable medical history presented with stellate foveal splitting of the outer plexiform layer on the right eye and peripheral splitting of the outer plexiform layer on both eyes. All known allegeable trigger factors for the existence of a hereditary or acquired foveomacular retinoschisis were ruled out either by clinical presentation or genetic testing. This led to the diagnosis of stellate nonhereditary idiopathic foveomacular retinoschisis with central involvement only present on one eye.

CONCLUSION

Although peripheral schisis of the outer plexiform layer is often concomitant with central splitting in X-linked juvenile retinoschisis, this is the first known report of nonhereditary cleavage of the outer plexiform layer of the peripheral retina without central affection in a patient with documented stellate nonhereditary idiopathic foveomacular retinoschisis on the other eye. These findings suggest an accurate bilateral examination of the peripheral retina while confirming the diagnose of stellate nonhereditary idiopathic foveomacular retinoschisis.