Novel mutations in the OPN1LW and NR2R3 genes in a patient with blue cone monochromacy

Background: To clarify the diagnosis of a Chinese patient with novel double heterozygous in the NR2E3 and OPN1LW genes and describe the clinical features.

Materials and methods: A 47-year-old man presented with an 8-year history of decreased vision and poor night vision. Based on his clinical phenotype, we focused on 36 genes associated with these characteristics. Possible pathogenic mutation sites were screened by next-generation sequencing (NGS), which showed novel mutations in the NR2E3 and OPN1LW genes. These mutations were confirmed in the patient's sister and daughter by Sanger sequencing. To clarify the diagnosis, the clinical symptoms of the patient were observed and analyzed in combination with comprehensive ophthalmologic examinations.

Results: Genetic analysis identified the presence of novel double heterozygous of c.361G>A; p.E121K in NR2E3, a gene responsible for enhanced S-cone syndrome (ESCS; OMIM #268100) and c.244A>G; p.K82E in OPN1LW, a gene responsible for blue cone monochromacy (BCM; OMIM#303700). No typical clinical presentation or fundus features were found. The differential diagnosis of ESCS was excluded by electroretinography (ERG) due to the lack of characteristic abnormalities associated with ESCS. Based on the clinical manifestations and comprehensive ophthalmologic examinations, the patient was diagnosed with BCM.

Conclusions: The novel mutations of c.244A>G; p.K82E in the OPN1LW gene and c.361G>A; p.E121K in the NR2E3 gene both cause BCM, but OPN1LW gene mutation dominated the retinal degeneration, resulting in the clinical features observed in this patient. These novel double heterozygous may be helpful for future genetic diagnosis and treatment for BCM.