Macular staphyloma in patients affected by Joubert syndrome with retinal dystrophy: a new finding detected by SD-OCT

Retinitis Pigmentosa Sine Pigmento in a Patient With a Heterozygous Mutation on the KIF7 Gene: A Case Report

Mutations in the KIF7 gene have been implicated in autosomal recessive conditions such as Joubert syndrome, acrocallosal syndrome, and fetal hydrolethalus, as well as in retinal degeneration and other ocular manifestations due to their effect on primary cilia. In this study, we report that the full-field electroretinogram (ERG) test showed non-recordable scotopic ERG responses, while photopic ERG responses were diminished bilaterally. This is a case report of a 62-year-old female patient with painless, progressive vision loss in both eyes. Fundus examination revealed a pale optic nerve head, vessel attenuation, and macular thinning without peripheral pigmentary changes. The full-field electroretinogram (ERG) test showed non-recordable scotopic ERG responses, while photopic ERG responses were diminished bilaterally. Based on these ocular findings, the patient was clinically diagnosed with retinitis pigmentosa (RP) sine pigmento. Genetic testing identified a pathogenic heterozygous mutation in the KIF7 gene with the variant c.61C>T (p.Arg21*). Our case suggests that this pathologic variant may be associated with RP sine pigmento. Further studies are warranted to better understand the role of the KIF7 gene in retinal dystrophies.

Genotype-phenotype correlates in Joubert syndrome: A review

Joubert syndrome (JS) is a genetically heterogeneous primary ciliopathy characterized by a pathognomonic cerebellar and brainstem malformation, the “molar tooth sign,” and variable organ involvement. Over 40 causative genes have been identified to date, explaining up to 94% of cases. To date, gene‐phenotype correlates have been delineated only for a handful of genes, directly translating into improved counseling and clinical care. For instance, JS individuals harboring pathogenic variants in TMEM67 have a significantly higher risk of liver fibrosis, while pathogenic variants in NPHP1, RPGRIP1L, and TMEM237 are frequently associated to JS with renal involvement, requiring a closer monitoring of liver parameters, or renal functioning. On the other hand, individuals with causal variants in the CEP290 or AHI1 need a closer surveillance for retinal dystrophy and, in case of CEP290, also for chronic kidney disease. These examples highlight how an accurate description of the range of clinical symptoms associated with defects in each causative gene, including the rare ones, would better address prognosis and help guiding a personalized management. This review proposes to address this issue by assessing the available literature, to confirm known, as well as to propose rare gene‐phenotype correlates in JS.

Broadening INPP5E phenotypic spectrum: detection of rare variants in syndromic and non-syndromic IRD

Pathogenic variants in INPP5E cause Joubert syndrome (JBTS), a ciliopathy with retinal involvement. However, despite sporadic cases in large cohort sequencing studies, a clear association with non-syndromic inherited retinal degenerations (IRDs) has not been made. We validate this association by reporting 16 non-syndromic IRD patients from ten families with bi-allelic mutations in INPP5E. Additional two patients showed early onset IRD with limited JBTS features. Detailed phenotypic description for all probands is presented. We report 14 rare INPP5E variants, 12 of which have not been reported in previous studies. We present tertiary protein modeling and analyze all INPP5E variants for deleteriousness and phenotypic correlation. We observe that the combined impact of INPP5E variants in JBTS and non-syndromic IRD patients does not reveal a clear genotype-phenotype correlation, suggesting the involvement of genetic modifiers. Our study cements the wide phenotypic spectrum of INPP5E disease, adding proof that sequence defects in this gene can lead to early-onset non-syndromic IRD.

Visual Evoked Potentials in Joubert Syndrome: A Suggested Useful Method for Evaluating Future Approaches Targeted to Improve Visual Pathways' Function

Introduction

Joubert syndrome (JS) is a recessive disorder characterized by a congenital malformation of the mid-hindbrain and a large spectrum of clinical features including optic nerve morphologic abnormalities. The function of the visual pathways, including the optic nerve, can be objectively evaluated by visual evoked potential (VEP) recordings. Our work aims to employ VEP to evaluate the neural conduction along the visual pathways in JS patients with or without optic nerve morphologic abnormalities (ONMA).

Methods

In this observational and prospective study, 18 children with genetic diagnosis of JS (mean age 8.78 ± 5.87 years) and 17 healthy age-similar control subjects (control group, 9.05 ± 6.02 years) were enrolled.

Based on presence/absence of ONMA at fundus examination, JS patients were divided into two groups: the JS-A group (eight patients with ONMA) and JS-N group (ten patients without ONMA). Following the ISCEV standards, pattern VEPs were recorded in patients and controls in response to 60’ and 15’ checks to obtain a prevalent activation of large or small axons, respectively.

Results

Compared to controls, both the JS-A and JS-N groups showed significant abnormalities in 60’ and 15’ VEP implicit time and amplitude. Only in the JS-N group were values of 15’ VEP implicit significantly correlated with the corresponding values of visual acuity.

Conclusions

Our results suggest that a visual pathways dysfunction (of both large and small axons) detectable by VEP may occur in JS patients regardless of the presence of ONMA. Since clinical trials are envisaged in the near future to address JS-related ocular problems, our results might provide information about the potential usefulness of VEP recordings to assess the efficacy of treatments targeted to improve the visual pathways’ function.

Relationship Between Macular Curvature and Common Causative Genes of Retinitis Pigmentosa in Japanese Patients

Purpose

To determine the relationship between the macular curvature and the causative genes of retinitis pigmentosa (RP).

Methods

We examined the medical records of the right eyes of 65 cases with RP (31 men and 34 women; average age, 47.6 years). There were 31 cases with the EYS variants, 11 cases with the USH2A variants, six cases with the RPGR variants, 13 cases with the RP1 variants, and four cases with the RP1L1 variants. The mean curvature of Bruch's membrane was calculated within 6 mm of the fovea as the mean macular curvature index (MMCI, 1/µm). We used multiple linear regression analysis to determine the independence of the causative genes contributing to the MMCIs after adjustments for age, sex, axial length, and width of the ellipsoid zone.

Results

The median MMCI was −31.2 × 10⁻⁵/µm for the RPGR eyes, −16.5 × 10⁻⁵/µm for the RP1L1 eyes, −13.0 × 10⁻⁵/µm for the RP1 eyes, −9.8 × 10⁻⁵/µm for the EYS eyes, and −9.0 × 10⁻⁵/µm for the USH2A eyes. Compared with the EYS gene as the reference gene, the RPGR gene was significantly related to the MMCI values after adjusting for the other parameters (P = 5.30 × 10⁻⁶). In contrast, the effects of the other genes, USH2A, RP1, and RP1L1, were not significantly different from that of the EYS gene (P = 0.26, P = 0.49, and P = 0.92, respectively).

Conclusions

The RPGR gene had a stronger effect on the steep macular curvature than the other ciliopathy-related genes.

Posterior staphylomas in non-highly myopic eyes with retinitis pigmentosa

PURPOSE

Our aim was to highlight the presence and the frequency of posterior staphyloma (PS) in non-highly myopic retinitis pigmentosa (RP) patients and to study the relationship between PS and choroidal thickness (CT).

METHODS

This was a retrospective case-control study of 77 eyes (39 patients) with RP, axial length inferior to 26 mm and clinically preserved macular area. All patients underwent fundus photography, A- and B-scan ocular ultrasonography, fundus autofluorescence (FAF) and swept source optical coherence tomography (SS-OCT). PS was defined by an outward bowing of the sclera on SS-OCT and B-scans. The relationship between the PS and SS-OCT layers thicknesses was determined.

RESULTS

Over 77 RP eyes of 39 patients studied, a PS was identified in 17 eyes (22%) of nine patients. Fifteen eyes had a narrow macular staphyloma (NMS), and two eyes had a wide macular staphyloma (WMS). Mean age in this group was 34.2 years (range 19-53 years), mean axial length was 23.60 ± 0.61 mm and mean CT was 185.7 ± 71 um versus 259.7 um in eyes without PS. The staphyloma edges corresponded to area of outer retina loss on SS-OCT and were larger than the hyperautofluorescent ring on FAF. We found a significant association between PS and CT in our RP patients (p = 0.003). The mean CT was significantly thinner in PS eyes compared to eyes without staphyloma. There was no significant association between PS and with visual acuity, years of progression, retinal thickness nor FAF findings.

CONCLUSIONS

PS was present in 22% of non-highly myopic eyes with RP. Narrow macular staphyloma was the most common type observed in our series. A marked thinning of the choroid was noted in PS eyes when compared to RP eyes without PS, as well as the outer retina degeneration.

Steeper Macular Curvature in Eyes With Non-Highly Myopic Retinitis Pigmentosa

Purpose

A posterior staphyloma has been reported to be present in some eyes with retinitis pigmentosa (RP), and the purpose of this study was to determine the macular curvature of non-highly myopic RP eyes.

Methods

This was a retrospective, observational study. The medical charts of the right eyes of 143 patients with RP and 60 controls whose axial length ranged from 21.5 mm to 26.0 mm were reviewed. The mean curvature of Bruch's membrane within 6 mm of the central macula obtained from the horizontal optical coherence tomographic images were evaluated as the mean macular curvature index (MMCI). The relationships between the MMCI and other clinical factors were assessed.

Results

The mean MMCI of RP patients (-13.73 ± 9.63 × 10-5 μm-1) was significantly lower than that of the controls (-6.63 ± 5.63 × 10-5 μm-1). This indicated a deeper concave shape of the macula in RP eyes (P < 0.001). The MMCI was significantly correlated with the age (r = 0.20; P = 0.016) and the axial length (r = -0.24; P = 0.004). Further analysis suggested a nonlinear effect of the ellipsoid zone width on the macular curvature in the RP eyes.

Conclusions

There is a high incidence of steeper macular curvatures even in non-highly myopic RP eyes, and the steepness was also affected by the degree of photoreceptor degeneration.

Severe retinitis pigmentosa with posterior staphyloma in a family with c.886C>A p.(Lys296Glu) RHO mutation

Background: Posterior pole staphylomata (PSS) is an outward bulging of ocular wall, rarely reported in association with inherited retinal degenerations. Patients and methods: We report a large French family of Jewish ancestry with a peculiar form of dominant retinitis pigmentosa (RP) and posterior pole staphyloma (PPS). Eight members were clinically and genetically examined. Results: All affected members complained of night blindness from early childhood and their ERGs were extinguished in the first decade of life. Seven out of eight presented PPS on fundus examination and SD-OCT. The youngest patient did not present PPS at 11 months of age, but the signs of posterior pole bowing became evident at age 8 years. There was no association between the presence of PPS and refraction. Patients with PPS were either hyperopic or myopic, but all have a high with-the-rule astigmatism. A myopic shift was observed for all of them at follow-up. In this family, the disease segregated with the c.886A>G mutation in RHO gene. Conclusion: A PPS development was observed in initially non-myopic patients of a family with unusually severe dominant RP. The PPS concerned only the area with relatively preserved outer retinal layers (outer nuclear layer and ellipsoid zone). How the outer retina could guide choroid and scleral remodelling remains unclear.