Clinical and molecular characterization of enhanced S-cone syndrome in children

Enhanced S-cone syndrome (ESCS) forms part of the differential diagnosis of night blindness in childhood.

To report in detail the clinical phenotype and molecular genetic findings in a series of children with ESCS.

Nine children with ESCS from 5 families underwent full ophthalmic examination, electrophysiological testing, and retinal imaging at a genetic eye disease clinic of a tertiary referral eye hospital. Bidirectional Sanger sequencing of all exons and intron-exon boundaries of NR2E3 was performed.

Results of ophthalmic examination and sequence analysis of NR2E3.

In total, 5 girls and 4 boys with a diagnosis of ESCS were included in the study. All patients had developed nyctalopia from early childhood. Visual acuity ranged from 0.00 to 1.20 logMAR (20/20 to 20/320 Snellen). All patients had hyperopia. Three patients had nummular pigmentary lesions along the arcades as typically seen in adults, 4 patients had mild pigmentary disturbance or white dots along the arcades, and 2 patients had a normal retinal appearance, although their fundus autofluorescence imaging demonstrated foci of increased autofluorescence along the arcades. Three patients had macular schisis-like changes on optical coherence tomography. Eight patients had electrophysiological testing at a mean age of 8.6 years (age range, 3-14 years), and in each patient the findings were consistent with the diagnosis of ESCS. Direct sequencing of NR2E3 identified 3 previously described mutations and 4 novel mutations. Seven patients were compound heterozygous for mutations in NR2E3, and 2 additional sibling patients were presumed to be homozygous for a missense change based on parental sequencing.

In this sample, children with ESCS had an early onset of night blindness and hyperopia but no nystagmus. Based on this study, children with ESCS may initially manifest a normal fundus appearance but later develop mottled retinal pigment epithelium change along the arcades, followed by the appearance of white dots in the same distribution. Fundus autofluorescence imaging is abnormal in children with a normal fundus appearance. The electrophysiological findings are pathognomonic and allow targeted molecular screening and a specific diagnosis.