Blue Cone Monochromacy Causes Deterioration in Visual Acuity and Color Vision in a Boy

Purpose: To present the genetic cause of progressive deterioration in visual acuity and color vision in a child with high myopia and strabismus. Here we describe a novel x-linked mutation in the opsin 1 medium-wave-sensitive (OPN1MW) gene in a child, leading to cone rod dystrophy. Setting/Venue: Trio whole-exome sequencing (WES). Methods: We reviewed the clinical data and eye exams including family history since the patient's first visit 2008. Further evaluation included fundus photography, optical coherence tomography and electroretinography. The child was also referred to neurological assessment and magnetic resonance imaging was performed. Genetic evaluation included the extraction of DNA from peripheral blood leukocytes, trio WES and bioinformatics analysis using the Burrows-Wheeler Aligner (BWA) and the Genome Analysis Tool Kit (GATK) software. Results: A normal eye examination showed that the parents and brothers were healthy. The boy had bilateral impaired vision (best visual corrected 1/24), high myopia (BE -7.0 diopter) and esotropia. On fundus exam, normal fundus appearance was reported with only mild temporal pallor of the optic discs. Retinal thickness measured by optical coherence tomography was within normal limits. Electrophysiological studies were unspecified for cone rod dystrophy based on photopic and scotopic responses. The complete neurology examination and neuroimaging were normal. WES revealed no compound heterozygosity or recessive mutations. Conclusions: Here we described a boy with severely impaired vision, not explained by the high myopia or the strabismus, who also had a progressive course. The family history was negative. Genetic evaluation revealed a deletion of exon 5 in the OPN1MW gene. He was diagnosed with a blue cone monochromacy. This child is a representative case with the common symptoms that are sometimes under-diagnosed without genetic evaluation.