Genetic and phenotypic presentation of Usher syndrome - a case report

Usher syndrome is a genetic, clinically heterogeneous condition characterized by sensorineural hearing loss, progressive retinal degeneration, and vestibular dysfunction. There are three phenotypically recognizable types of Usher syndrome. Individuals with Usher syndrome type 1 have no vestibular function and profound sensorineural hearing loss. Individuals with Usher syndrome type 2 have normal vestibular function and mild-to-severe hearing loss with visual impairment that is presented later in life. People with Usher syndrome type III experience hearing and vision loss beginning later in life. In this case report, we are reporting a 7-year-old boy consulted for progressive hearing loss and bilateral vision impairment, and fundus exam revealed mild bilateral retinal vessel attenuation and bone spicule deposits in both eyes. A molecular genetic test done by next-generation sequencing identified a homozygous pathogenic variant in the CDH23 gene (NM_022124.5:c.2255del variant coordinate with amino acid change of p.(Gly752Valfs*13)), confirming the diagnosis of autosomal recessive Usher syndrome type ID (USH1D). The patient had a remarkable improvement with visual and optical aids. Genetic counseling, including reproductive counseling, was provided to the parents. Clinical evaluation, visual hearing tests, and genetic workup confirmed Usher syndrome, which is a rare but dangerous cause of hearing loss and visual impairment that needs to be thoroughly evaluated by a multi-disciplinary team approach.