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PHENOTYPE-GUIDED GENETIC TESTING OF PEDIATRIC INHERITED RETINAL DISEASE IN THE UNITED ARAB EMIRATES
Arif O Khan1,2
1Eye Institute, Cleveland Clinic Abu Dhabi, Abu Dhabi, United Arab Emirates; and.
Insights
Genetic testing identified mutations in 26 retinal disease genes in Emirati children with inherited retinal disease. Recessive mutations were common, with specific founder mutations identified, aiding diagnosis and management.
Area of Science:
- Ophthalmology
- Genetics
- Pediatrics
Background:
- Inherited retinal diseases (IRDs) are prevalent in the Arabian Gulf.
- Limited data exists on pediatric IRDs in this region.
- Ocular genetics services are crucial for diagnosis.
Purpose of the Study:
- To describe the experience of an Ocular Genetics Service with childhood-onset IRD in the UAE.
- To identify genetic causes of IRD in Emirati children.
- To evaluate diagnostic yield of phenotype-guided genetic testing.
Main Methods:
- Retrospective analysis of 71 Emirati pediatric IRD patients (2016-2018).
- Clinical phenotypes guided genetic testing (single gene, panel, exome sequencing).
- Identified disease-causing mutations in 26 retinal disease genes.
Main Results:
- Majority of patients presented with visual problems before age 5.
- Recessive IRDs were frequently caused by homozygous mutations.
- Most common genes: ABCA4 (14), KCNV2 (8), CRB1 (6), CNGA3 (5).
- Identified recurrent mutations, including potential founder mutations.
Conclusions:
- Phenotype-guided genetic testing demonstrated high diagnostic yield.
- Homozygous mutations are a frequent cause of recessive IRDs.
- Cone-dominated phenotypes and founder mutations were observed.
- Molecular diagnosis is vital for early identification of syndromic IRDs, minimizing morbidity.
Purpose:
Inherited retinal disease is relatively common in the Arabian Gulf, but details regarding pediatric inherited retinal disease in the region are lacking. The purpose of this study is to report the experience of a regional Ocular Genetics Service with childhood-onset inherited retinal disease in the United Arab Emirates.
Methods:
Retrospective series of consecutive Emirati patients referred to the Ocular Genetics Service of Cleveland Clinic Abu Dhabi over a 3-year period (2016-2018) who were diagnosed with childhood-onset inherited retinal disease (onset before 16 years old) and underwent diagnostic genetic testing guided by clinical phenotype (single gene, next-generation panel, or exome sequencing).
Results:
Seventy-one probands were identified (38 male and 33 females), the majority of whom were symptomatic with visual problems within the first 5 years of life. All patients had disease causing mutations in 1 of 26 retinal disease genes. Recessive disease was frequently due to homozygous mutations. The most frequently mutated genes (and number of probands) were ABCA4 (14), KCNV2 (8), CRB1 (6), and CNGA3 (5). Recurrent specific gene mutations included ABCA4 p.Gly1961Glu/p.Leu857Pro, KCNV2 p.Glu143*, MERTK p.Cys738Trpfs*32, and RS1 c.52+3A>G. Some probands had mutations in syndromic genes and were confirmed to have extraocular findings.
Conclusion:
Phenotype-guided genetic testing had a remarkable yield for this patient population. Recessive disease is often from homozygous mutations. Cone-dominated phenotypes are common. There are apparent founder mutations for several genes that could be used in a targeted genetic testing strategy. Molecular diagnosis is particularly important in affected children when inherited retinal dystrophy could be a sign of syndromic disease as proper earlier diagnosis minimizes potential extraocular morbidity.
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