Usher Syndrome and Color Vision

Elaborate Evaluation of Farnsworth Dichotomous D-15 Panel Test Can Help Differentiate between Best Vitelliform Macular Dystrophy and Autosomal Recessive Bestrophinopathy

INTRODUCTION

The colour vision in bestrophinopathies has not been assessed in detail so far. The aim of this study was to explore the extent to which distinct types of bestrophinopathies differ in regard to colour vision deficiencies using Farnsworth Dichotomous D-15 and Lanthony Desaturated D-15 panel tests.

METHODS

Both D-15 tests were performed in 52 eyes of 26 patients with Best vitelliform macular dystrophy (BVMD) and 10 eyes of 5 patients with autosomal recessive bestrophinopathy (ARB). Two methods were used for a quantitative assessment of the colour vision deficiencies: moment of inertia method and Bowman method. The following parameters were calculated: confusion angle, confusion index (C-index), selectivity index (S-index), total error score (TES), and colour confusion index (CCI).

RESULTS

The median value of confusion angle for all stages of BVMD fell into a narrow range around 62, indicating normal results. The median confusion angle value was 57 in ARB patients within a very wide range down to -82, indicating non-specific deficits. These differences were statistically significant. Significantly abnormal C-index and CCI values were found only in ARB patients, being 2.0 and 1.49, respectively. The majority of parameters of D-15 tests were independent of the visual acuity in both bestrophinopathies.

CONCLUSIONS

Elaborate evaluation of the D-15 panel tests might help establish a differential diagnosis between different bestrophinopathies, as the pattern of the colour vision loss is different between BVMD and ARB. The quantitative parameters of colour vision tests in bestrophinopathies are independent of the visual acuity.

Pathogenicity reclassification of the RPE65 c.1580A>G (p.His527Arg) - a case report

BACKGROUND

It is of utmost importance to define the molecular diagnosis of patients with retinitis pigmentosa (RP) due to existing targeted therapeutic option: voretigene neparvovec.We provide clinical evidence for pathogenicity reclassification of variants of uncertain significance (VUSs) RPE65 c.1580A>G (p.His527Arg).

MATERIALS AND METHODS

A case report of a 10-year-old boy with progressive vision loss. The patient manifested disease highly suggestive of RPE65 retinal dystrophy: nyctalopia, fairly good central vision, severely depressed full-field electroretinography responses and complete loss of peripheral fundus aut ofluorescence.

RESULTS

Invitae Inherited Retinal Disorders Panel identified likely pathogenic mutation RPE65 c.499G>T (p.Asp167Tyr) and RPE65 c.1580A>G (p.His527Arg), variant of uncertain significance. Segregation analysis confirmed that these variants are in trans.

CONCLUSIONS

We conclude that the variant RPE65 c.1580A>G (p.His527Arg) has contributed to the pathologic phenotype, demonstrating its significance clearly in the case presented, and should be reclassified according to the criteria of evidence as pathogenic. Therefore, patients with this specific variant in homozygous or compound heterozygous form would likely benefit from genetic treatment based on recombinant adeno-associated virus vector, providing a working RPE65 gene to act in place of a mutated RPE65 gene.

The Importance of Early Genetic Diagnostics of Hearing Loss in Children

Hearing loss is one of the most common sensory deficits. It carries severe medical and social consequences, and therefore, universal newborn hearing screening was introduced at the beginning of this century. Affected patients can have hearing loss as a solitary deficit (non-syndromic hearing loss) or have other organs affected as well (syndromic hearing loss). In around 60% of cases, congenital hearing loss has a genetic etiology, where disease-causing variants can change any component of the hearing pathway. Genetic testing is usually performed by sequencing. Sanger sequencing enables analysis of the limited number of genes strictly preselected according to the clinical presentation and the prevalence among the hearing loss patients. In contrast, next-generation sequencing allows broad analysis of the numerous genes related to hearing loss, exome, or the whole genome. Identification of the genetic etiology is possible, and it makes the foundation for the genetic counselling in the family. Furthermore, it enables the identification of the comorbidities that may need a referral for specialty care, allows early treatment, helps with identification of candidates for cochlear implant, appropriate aversive/protective management, and is the foundation for the development of novel therapeutic options.