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Phenotypic variation in enhanced S-cone syndrome
Isabelle Audo1, Michel Michaelides, Anthony G Robson
1Department of Electrophysiology, Moorfields Eye Hospital, 162 City Road, London, United Kingdom.
Investigative Ophthalmology & Visual Science
|April 26, 2008
Summary
Enhanced S-cone syndrome (ESCS) presents a variable clinical and electrophysiological phenotype, often dominated by short-wavelength-sensitive mechanisms. Genetic analysis revealed NR2E3 mutations in most patients, highlighting the syndrome
Area of Science:
- Ophthalmology and genetics
- Retinal electrophysiology
- Cone photoreceptor function
Background:
- Enhanced S-cone syndrome (ESCS) is a rare inherited retinal disorder.
- The clinical and genetic basis of ESCS requires further elucidation.
- Understanding the phenotype-genotype correlation is crucial for diagnosis and management.
Purpose of the Study:
- To characterize the clinical, psychophysical, and electrophysiological phenotype of 19 ESCS patients.
- To correlate the observed phenotype with underlying genetic mutations in the NR2E3 gene.
- To investigate the functional contribution of S-cones and other retinal mechanisms in ESCS.
Main Methods:
- Comprehensive ophthalmic examinations and functional tests including pattern ERG, full-field ERG, and short-wavelength stimulation.
- Advanced imaging techniques such as multifocal ERG, fundus autofluorescence, OCT, and FFA were employed.
- NR2E3 mutational screening was performed in a subset of patients.
Main Results:
- Fundus appearance varied from normal to pigmentary changes; foveal schisis was present in nine patients.
- All patients exhibited abnormal pattern ERGs; rod-specific ERGs were undetectable, and flicker ERGs were delayed.
- ERG responses were predominantly mediated by short-wavelength-sensitive mechanisms, with novel NR2E3 variants identified in 12/13 patients.
Conclusions:
- ESCS exhibits a variable phenotype in terms of fundus appearance and electrophysiological severity.
- Electrophysiological findings are largely driven by short-wavelength-sensitive mechanisms.
- The presence of OFF-related ERG activity in most patients is an atypical finding for S-cone related disorders.
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