Genetics of Inherited Retinal Diseases in Understudied Populations

Leber congenital amaurosis: A clinical and genetic study from a tertiary eye care center

PURPOSE

To assess the clinical phenotypes and genetic mutations in patients with Leber congenital amaurosis (LCA) from a tertiary eye care center in India.

DESIGN

Retrospective observational study.

METHODS

The study includes patients with a clinical diagnosis of LCA who underwent genetic testing from January 2016 to December 2021. The clinical exome of the patients was analyzed by targeted next-generation sequencing. The genetic variants found were classified as per standard American College of Medical Genetics and Genomics (ACMG) criteria and ClinVar database.

RESULTS

There were 35 patients (19 females, 16 males) of LCA. Family history was positive in 29% (10/35) and a history of consanguinity was noted in 54% (19/35) of the patients. The mean presenting best-corrected visual acuity was 2.48 ± 0.59 logMAR. Retinal pigment epithelial abnormalities and macular involvement were seen in 83% (58/70) and 23% (16/70) of the eyes, respectively, at presentation. The most common causative genes for LCA in our cohort were: GUCY2D (20%, 7/35), CRB1 ( 14%, 5/35), RPE65 ( 11%, 4/35), RPGRIP1 ( 11%, 4/35), and LCA5 ( 9%, 3/35). Autosomal recessive inheritance was seen in 94% (33/35). Macular involvement at presentation was seen in CRB1 (3/5), NMNAT1 (2/2), and one each of RPE65 , LCA5 , and RDH12 patients. The genetic testing cost was reduced from 23,800 INR to 15,000 INR per test in the study duration.

CONCLUSIONS

Genetic screening of LCA cases identified various genotypes, with GUCY2D being the most common. Increased awareness and reduced costs of genetic testing would benefit both patients and caregivers. With promising clinical trial outcomes, genotyping is crucial for better patient selection and treatment.

Genetics and phenotypes of RPE65 mutations in inherited retinal degeneration: A study from a tertiary eye care center in Brazil

Purpose

Biallelic variants in the retinal pigment epithelium-specific 65-kDa protein (RPE65) gene are linked to several inherited retinal diseases (IRDs), including Leber congenital amaurosis (LCA), early-onset severe retinal dystrophy (EOSRD), and retinitis pigmentosa (RP). This study screened patients from a tertiary center in Brazil with IRDs for RPE65 variants to characterize the associated phenotypes.

Methods

LCA, EOSRD, and RP diagnoses were based on predefined clinical criteria. Patients underwent comprehensive clinical evaluations and retinal imaging. Genomic DNA was analyzed using a next-generation sequencing panel for IRDs, covering 238 genes.

Results

RPE65 variants were identified in seven of the 68 patients screened. Of these, three were homozygous, and four were compound heterozygous for the identified mutant alleles. A total of six variants were detected, of which one was novel. The p.Leu341Ser (c.1022T>C) mutation was the most prevalent, being found in four of seven patients. Visual loss onset ranged from birth to the third decade of life. A consistent clinical feature observed in all patients was some degree of pigmentary change upon peripheral retinal examination.

Conclusions

RPE65 variants were found in 10.3% of cases in this series, associated with LCA, EOSRD, and RP. These variants were consistently linked with pigmentary changes in the peripheral retina and exhibited variable manifestations regarding arteriolar attenuation, disc pallor, and macular appearance. In this series, the prevalence of the p.Leu341Ser (c.1022T>C) mutation was 57%.

RPE65 mutations in Leber congenital amaurosis, early-onset severe retinal dystrophy, and retinitis pigmentosa from a tertiary eye care center in India

INTRODUCTION

Mutations in the retinal pigment epithelial 65 kilodalton protein (RPE65) gene are associated with various inherited retinal diseases (IRDs), including Leber congenital amaurosis (LCA), early-onset severe retinal dystrophy (EOSRD), and retinitis pigmentosa (RP). We screened for mutations in RPE65 in a series of Indian patients with these IRDs to determine the frequency/types of mutations and to describe the associated phenotypes.

MATERIALS AND METHODS

Diagnosis of LCA, EOSRD, and RP was made by standard and pre-defined criteria. Patients were evaluated by clinical, retinal imaging, and electrophysiological parameters. Genomic DNA from patients and available family members were used for identifying mutations by direct Sanger sequencing of the RPE65 gene or targeted NGS gene panel for IRDs covering 260+ genes. Variations detected were tested in healthy control populations and for co-segregation with the disease in available family members.

RESULTS

Mutations were found in eight patients, out of 220 total cases screened, all homozygous for the respective mutant alleles. Seven patients had mutations leading to premature termination codons and one patient had a missense change. The onset of visual loss ranged from birth to <2 years of life. At presentation, RPE mottling in the background retina was present in all cases with macular involvement in five cases with or without vascular attenuation and optic disc pallor.

CONCLUSION

RPE65 mutations in this series were found in 3.6% of cases associated with severe, early-onset disease, with consistent RPE mottling and variable manifestations with regard to the extent of disc pallor, arteriolar attenuation, and appearance of the macula.

Cost-of-illness studies of inherited retinal diseases: a systematic review

BACKGROUND

While health care and societal costs are routinely modelled for most diseases, there is a paucity of comprehensive data and cost-of-illness (COI) studies for inherited retinal diseases (IRDs). This lack of data can lead to underfunding or misallocation of resources. A comprehensive understanding of the COI of IRDs would assist governmental and healthcare leaders in determining optimal resource allocation, prioritizing funding for research, treatment, and support services for these patients.

METHODS

Following PRISMA guidelines, a literature search was conducted using Medline, EMBASE and Cochrane databases, from database inception up to 30 Jun 2023, to identify COI studies related to IRD. Original studies in English, primarily including patients with IRDs, and whose main study objective was the estimation of the costs of IRDs and had sufficiently detailed methodology to assess study quality were eligible for inclusion. To enable comparison across countries and studies, all annual costs were standardized to US dollars, adjusted for inflation to reflect their current value and recalculated on a "per patient" basis wherever possible. The review protocol was registered in PROSPERO (registration number CRD42023452986).

RESULTS

A total of nine studies were included in the final stage of systematic review and they consistently demonstrated a significant disease burden associated with IRDs. In Singapore, the mean total cost per patient was roughly US$6926/year. In Japan, the mean total cost per patient was US$20,833/year. In the UK, the mean total cost per patient with IRD ranged from US$21,658 to US$36,549/year. In contrast, in the US, the mean total per-patient costs for IRDs ranged from about US$33,017 to US$186,051 per year. In Canada, these mean total per-patient costs varied between US$16,470 and US$275,045/year. Non-health costs constituted the overwhelming majority of costs as compared to healthcare costs; 87-98% of the total costs were due to non-health costs, which could be attributed to diminished quality of life, poverty, and increased informal caregiving needs for affected individuals.

CONCLUSION

IRDs impose a disproportionate societal burden outside health systems. It is vital for continued funding into IRD research, and governments should incorporate societal costs in the evaluation of cost-effectiveness for forthcoming IRD interventions, including genomic testing and targeted therapies.