Correlation between Genotype and Phenotype in 69 Chinese Patients with USH2A Mutations: A comparative study of the patients with Usher Syndrome and Nonsyndromic Retinitis Pigmentosa.

PURPOSE: The aim of this study was to analyse 69 Chinese patients with USH2A mutations and to assess the genotype-phenotype correlation.

METHODS

All 36 Usher syndrome type IIA patients and 33 nonsyndromic RP (retinitis pigmentosa) patients underwent clinical examinations. Eye examinations included best-corrected visual acuity, slit-lamp biomicroscopy, fundus examination with dilated pupils, fundus fluorescent angiography, visual field test, full-field electroretinography and optic coherence tomography; audiological assessment included pure tone audiometry and hearing thresholds. The molecular diagnosis of genotype combined the single-gene Sanger sequencing and next-generation sequencing. This study is a retrospective study.

RESULTS

The mean age of first symptoms with Usher syndrome type IIa and nonsyndromic RP patients was 13.7 versus 29.8 years (ocular phenotypes, p < 0.001); 17.7 versus 29.9 years (nyctalopia, p < 0.001); 44.7 versus 54.8 years (low vision based on VF, p < 0.001); 41.7 versus 54.7 years (low vision based on VA, p < 0.001); and 46.0 versus 56.7 years (legal blindness based on VF, p < 0.001). There was significant difference in variants in the two groups (p < 0.05). Among patients with mutation c.2802T > G (p.Cys934Trp), more (66.7%) presented with normal hearing. All patients (3/3, 100%) with the variant c.8232G > C (p.Trp2744Cys) had hearing loss. Furthermore, we identified 23 novel variants in USH2A.

CONCLUSIONS

Patients with Usher syndrome type IIa had an earlier onset of the disease, inferior visual function and presented with more truncating variants, compared with the nonsyndromic RP patients.