Prevalence of inherited retinal diseases in a large Egyptian cohort

BACKGROUND

Inherited retinal diseases form a rare, highly heterogeneous group of genetic disorders characterized by retinal degeneration. It is considered one of the leading causes of debilitating visual loss and blindness in children and young adults. Despite this few population-based data studies on prevalence of inherited retinal diseases exist. Moreover, prevalence can vary widely depending on geographical area, population ethnicity and cultural habits.

PURPOSE

To report the prevalence of different subtypes of Inherited retinal diseases in a large Egyptian cohort in a retrospective, hospital-based, cross-sectional study.

METHODS

We conducted an extensive electronic medical record search for all the patients attending the outpatient clinic and investigation unit of Ain Shams University Hospital and the two branches of Watany Eye Hospital in the period between January 2015 and October 2022 aiming to identify the prevalence rate of different types of IRDs, patient demographics and stratify them according to their phenotype.

RESULTS

We examined the electronic medical records of 478 222 patients, 971 patients were diagnosed with IRD by clinical examination with or without any of the following investigations: color fundus photography, fundus autofluorescence, fundus fluorescein angiography, optical coherence tomography and/or electrophysiological studies as electroretinogram, visual evoked potential and electrooculogram. The overall prevalence was 0.2%. The most common IRD encountered was isolated retinitis pigmentosa with a percentage of 78.9% followed by Stargardt disease at 6.3%, cone-rod dystrophy at 2.0%, autosomal recessive bestrophinopathy at 1.9% and unspecified IRD at 1.5%.

CONCLUSION

Retinitis pigmentosa was the most common IRD encountered followed by Stargardt disease. Many of the dystrophies are the subject of clinical intervention trials, and population-based epidemiological data can guide phenotype-based genetic testing and help assess the future need for treatment.

Harel Yoon syndrome: a novel mutation in ATAD3A gene and expansion of the clinical spectrum

BACKGROUND

Harel-Yoon syndrome (HAYOS) is a recently described neurodevelopmental disorder characterized by psychomotor delay, truncal hypotonia, appendicular spasticity, and peripheral neuropathy. It is caused by mutations in ATAD3A gene located on chromosome 1p.36.33 whose functions include mitochondrial DNA stabilization, the regulation of mitochondrial fission/fusion, and cholesterol homeostasis.

MATERIALS AND METHODS

An 11-year-old male patient of consanguineous Egyptian parents, who present with neuroregression and ptosis along with progressive impaired vision, undergoes complete ophthalmological and neurological examination. Additionally, color fundus photography, fundus autofluorescence (FAF), spectral domain optical coherence tomography (SD-OCT) of both the macula and optic nerve head, full field electroretinogram (ERG), and visual field perimetry were obtained. Whole-exome sequencing and mitochondrial genome sequencing were done in a commercial laboratory from a peripheral blood sample.

RESULTS

A novel mutation in ATAD3A gene c.624_644del was identified by whole-exome sequencing consistent with a diagnosis of Harel-Yoon Syndrome (HAYOS). The 11-year-old boy had characteristic features of neurodevelopmental delay, hypotonia, and peripheral neuropathy. However, we documented some novel features as fatiguable ptosis, facial weakness, progressive bulbar palsy, obsessive-compulsive disorder (OCD) in addition to cone system dysfunction.

CONCLUSION

Our study reports a novel mutation in ATAD3A gene and expands the clinical spectrum of Harel-Yoon Syndrome. Future research aiming at better understanding of gene function will lead to better genotype-phenotype correlation and could pave the way to more treatment options.

Autosomal Recessive Bestrophinopathy Presenting With a Macular Hole Retinal Detachment

Purpose: To report a case of autosomal recessive bestrophinopathy (ARB) that presented with macular hole retinal detachment (MHRD). Methods: A case report. Results: A 31-year-old male patient presented with rapid deterioration of vision in the left eye. On fundus examination, bilateral retinal deposits in both eyes, which were brightly hyperautofluorescent, and an MHRD in the left eye could be detected. An electrooculogram demonstrated absent light rise with abnormal Arden’s ratio in both eyes. The patient was offered surgery for the MHRD but refused due to the guarded visual prognosis. Follow up of the patient after one year revealed progression of the retinal detachment. Genetic testing revealed a novel, homozygous missense mutation in the BEST1 gene, confirming the diagnosis of ARB. Conclusion: ARB can present with an MHRD. Counseling patients with inherited retinal dystrophies about the visual prognosis following surgical intervention is important.

Mutation analysis reveals novel and known mutations in SAG gene in first two Egyptian families with Oguchi disease

Background

Oguchi disease is a rare type of congenital stationary night blindness associated with an abnormal fundus appearance. It is inherited in an autosomal recessive manner where two types exist according to the gene affected; type 1 associated with S-antigen (SAG) gene mutations and type 2 associated with rhodopsin kinase (GRK1) gene mutations.

Purpose

The aim of this work was to describe the clinical and genetic findings of the first two reported families of Oguchi disease in Egypt and African region.

Methods

Four members of two consanguineous Egyptian families with history of night blindness since childhood underwent complete ophthalmological examination, standard automated static perimetry, fundus color photography, fundus autofluorescence (FAF), fundus fluorescein angiography (FFA) in light-adapted state and spectral-domain optical coherence tomography (SD-OCT) of both the macula and the optic nerve head as well as central corneal thickness with repeated fundus photography following prolonged dark adaptation. Mutation screening of 7 coding exons of GRK1 gene and 15 coding exons of SAG gene as well as some flanking regions were performed using Sanger sequencing technique. The variants were tested for pathogenicity using different in silico functional analysis tools.

Results

The clinical examination and investigations confirmed Oguchi disease phenotype. One patient showed p.R193* (c.577C > T) which is a previously reported SAG gene mutation in a homozygous form. The other three patients from a different family showed (c.649–1 G > C), a novel canonical splice site SAG gene mutation in a homozygous form.

Conclusion

The identification of the novel canonical splice site SAG gene variant in three members of the same family with clinically confirmed Oguchi disease reinforces its pathogenicity. A fourth patient from another family carried a previously reported mutation in the same gene. SAG gene variants may be the underlying genetic cause for Oguchi disease in Egypt. Our findings have expanded the spectrum of Oguchi disease-associated mutations in SAG gene and may serve as a basis for genetic diagnosis for Oguchi disease.

Exfoliation Syndrome in Egypt: Prevalence and Association with Cataract in a Large Cohort

INTRODUCTION

Exfoliation syndrome is an age-related disease leading to ocular and systemic complications. We aimed to evaluate the prevalence of exfoliation syndrome (XFS) in Egypt and its association with cataract as one of its comorbidities.

METHODS

In a retrospective, hospital-based study, 155,032 Egyptians aged over 40 years from all 27 Egyptian governorates were evaluated for the prevalence of XFS and cataract in the period between January 2015 and June 2020.

RESULTS

A total of 2448 (1.6%) of the studied subjects had XFS. Their mean age was 71.2 ± 9.62 years which was significantly higher than those of subjects with no XFS. Men comprised 1348 (55.1%) of those diagnosed with XFS and this association was statistically significant (OR 1.57, 95% CI 1.45-1.70). Considering the ratio between subjects in our cohort from each region and its real population, the overall corrected prevalence in Egypt was 4.49% (Territorial regions 6.89%, Upper Egypt 5.51%, Lower Egypt 4.38%, and Greater Cairo 3.29%). Among all subjects with XFS, cataract was found in 2150 subjects (87.8%) and XFS represented 6.4% of all subjects diagnosed with cataract in our cohort (n = 33,610). Among subjects with no cataract (n = 121,422), 298 subjects had XFS (OR 0.04, 95% CI 0.03-0.04).

CONCLUSION

Egypt has a moderate XFS prevalence compared to other countries. There is a strong association between XFS and cataract, and XFS was more common in elderly males. The results can be explained by differences in diet, ethnicity, climate, and maybe other factors.