Abstract
Usher syndrome has three subtypes, each being clinically and genetically heterogeneous characterised by sensorineural hearing loss and retinitis pigmentosa (RP), with or without vestibular dysfunction. It is the most common cause of deaf–blindness worldwide with a prevalence of between 4 and 17 in 100 000. To date, 10 causative genes have been identified for Usher syndrome, with MYO7A accounting for >50% of type 1 and USH2A contributing to approximately 80% of type 2 Usher syndrome. Variants in these genes can also cause non-syndromic RP and deafness. Genotype–phenotype correlations have been described for several of the Usher genes. Hearing loss is managed with hearing aids and cochlear implants, which has made a significant improvement in quality of life for patients. While there is currently no available approved treatment for the RP, various therapeutic strategies are in development or in clinical trials for Usher syndrome, including gene replacement, gene editing, antisense oligonucleotides and small molecule drugs.
Highlights
Usher syndrome encompasses a group of inher ited disorders characterised by dual sensory impairment of the auditory and visual systems, with a variable presentation of vestibular dysfunc tion in a proportion of cases
An additional small molecule that has been of interest for Usher syndrome treatment, known as BioFocus 844 (BF844), was identified through cell-based high throughput screening as capable for stabilising the defective Clarin-1 protein pro duced by the common CLRN1 missense variant p.(Asn48Lys).[138]
As the hearing loss is congenital and relatively stable throughout the lifetime of Usher patients, a number of natural history stud ies have focussed on the progress of the retinal disease in Usher patients; these have included longitudinal assessment of patients with MYO7A9,10,84,149 and USH2A9,98,150–152 muta tions using various clinical functional and struc tural measures, including visual acuity, perimetry, electro retinography (ERG), fundus autofluorescence and OCT-derived measurements
Summary
Usher syndrome encompasses a group of inher ited disorders characterised by dual sensory impairment of the auditory and visual systems, with a variable presentation of vestibular dysfunc tion in a proportion of cases.
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