Special clinical features with a novel mutation site of CHN1 gene in a Chinese family with Duane retraction syndrome.

PURPOSE: This study is to describe the special clinical and genotypic features of a Chinese family with variant types of Duane retraction syndrome and to present our experience on managing these cases.

METHODS: Four individuals from one family were reviewed by ophthalmologic examinations, in which two affected and two unaffected individuals were revealed. MRI scans were performed on the two patients. Relevant gene mutations were screened by the next-generation sequencing technology and confirmed by Sanger sequencing technology.

RESULTS: The six-year-old proband presented with special clinical features of severe horizontal gaze dysfunction, exotropia and mild scoliosis. His mother showed significantly limited binocular abductions, with retraction of eyeballs in adduction. From MRI scans, abducens nerves were not observed in both patients and the oculomotor nerve was slightly thin in the proband. The proband and his mother shared the same CHN1 gene mutation site (c. 62A>G; p.Y21C). Strabismus surgery was performed on the proband to correct the primary gaze exotropia.(NM_001822: exon3 or NM_001025201: exon4: c. 62A>G; p.Y21C).

CONCLUSIONS: A novel CHN1 gene mutation was revealed from a Chinese family with Duane retraction syndrome. Remarkably, the proband and his mother presented different clinical features of ocular motility disorder. Strabismus correction surgery and amblyopia training helped to improve the appearance and visual function of the proband.