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M. S. Galantuomo, I. Zucca, S. Banfi, C. Ziviello, G. Carboni, G. Forma, Y. Titi, M. Fossarello; A NR2E3 Mutation (R309G) Associated With a Mild Form of Enhanced S-Cone Syndrome. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2186.
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We investigated the ophthalmic features of a mild form of enhanced S-cone syndrome (ESCS) in a 9-year-old Sardinian female proband and 3 unaffected family members. A genetic analysis was performed.
Fundus examinations (fundus photography, fluorescein angiography and fundus autofluorescence (AF), optical coherence tomography (OCT), automatic perimetry (AP) (W/W and B/Y), color vision tests, and full-field and spectral electroretinography (ERG) were performed. Mutation screening of the NR2E3 gene, which encodes a photoreceptor-specific orphan nuclear receptor, was performed using an integrated strategy including the use of a microarray chip (available at Asperbio) that allows the screening of a large number of mutations already known to be responsible for autosomal recessive RP and direct sequencing analysis.
The diagnosis of ESCS was made based on the distinctive visual field (B/Y vs. W/W) and spectral ERG findings: hypersensitivity to blue stimuli and hyposensitivity to red stimuli. The proband had good visual acuity, normal color vision, good central VFs (B/Y better than W/W). Funduscopy showed pigment clumpings from the vascular arcades to the midperipheral retina. Fundus AF imaging revealed a wide disciform area of hyper-autofluorescence located in the macula. The OCT images showed a morphologically normal macular thickness in LE, and abnormal macular thickness related to cystoid edema in RE, which was responsive to oral acetazolamide. In the full-field ERG, low amplitudes of rod b-waves were detected. Waveforms between rod-plus-cone and cone ERGs were very similar. Mutation analysis identified a homozigous mutation, R309G, which resides in the ligand-binding domain (LBD). The unaffected parents carried one of these mutations each, consistent with autosomal recessive transmission.
Our study suggests that the expression of this mutant of NR2E3, is correlated with a mild form of ESCS, in that full foveal function and retinal laminar structure are maintained, and certain rod responses are present.
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