Bi-allelic pathogenic variants in NR2E3 may be associated with a subtle enhanced S-cone syndrome phenotype

To describe the phenotype of a patient with bi-allelic pathogenic variants in NR2E3 that did not result in an overt enhanced S-cone syndrome (ESCS) phenotype.

The patient underwent a comprehensive ophthalmic exam, imaging with spectral domain optical coherence tomography (SD-OCT) and fundus autofluorescence, and vision measured with kinetic and static chromatic perimetry and full-field electroretinography (ffERG).

A 60-year-old man presented with a history of blurred vision for at least 10 years. Visual acuities were 20/80 and 20/20 in the right and left eye, respectively. There was a mainly midperipheral pigmentary retinopathy with major interocular asymmetry. On SD-OCT, there were intraretinal cystic changes in the right eye and photoreceptor outer nuclear layer (ONL) thinning most obvious in superior retina, with steep transitions into normally laminated retina. ffERG showed moderately reduced amplitudes for rod- and cone-mediated responses without S-cone hyperfunction in each eye. Chromatic perimetry showed mildly reduce rod sensitivities co-localizing with reduced L/M cone function and unexpectedly normal or near normal S-cone sensitivities in the most affected eye. Genetic testing detected bi-allelic pathogenic variants in NR2E3 (c.119-2A > C and c.227 G > A) previously associated with ESCS.

Bi-allelic variants in NR2E3 previously reported in association with ESCS showed evidence of rod photoreceptor function, and thus, terminally differentiated rods. The topography of the resulting pigmentary retinopathy shares features of NR2E3-ESCS and local relationships between local L/M and S-cone dysfunction suggest a mild ESCS phenotype that can escape detection in the absence of classical ffERG retina-wide findings of this syndrome.