Usher syndrome type 3

Usher syndrome type 3 (USH3) is a rare autosomal recessive disorder characterized by the combination of progressive sensorineural hearing loss, retinitis pigmentosa (RP), and variable vestibular dysfunction. Unlike Usher syndrome types 1 and 2, where hearing loss is congenital and either profound or moderate-to-severe respectively, USH3 is distinguished by postlingual, progressive hearing loss that typically begins in childhood or adolescence and worsens over time. The retinal degeneration in USH3 also manifests as progressive night blindness and loss of peripheral vision due to retinitis pigmentosa, usually becoming apparent by the second to fourth decade of life, eventually leading to significant visual impairment or blindness. Vestibular function is variable, with some patients experiencing balance difficulties while others retain normal vestibular responses. Usher syndrome type 3 is primarily caused by mutations in the CLRN1 gene (also known as USH3A), which encodes clarin-1, a protein believed to play a role in the development and maintenance of sensory cells in the inner ear and retina. USH3 is particularly prevalent in the Finnish population and among Ashkenazi Jewish individuals due to founder mutations. The condition is sometimes referred to as Usher syndrome type IIIA or USH3A. There is currently no cure for Usher syndrome type 3. Management is supportive and multidisciplinary, involving regular audiological assessments, hearing aids or cochlear implants for progressive hearing loss, and ophthalmological monitoring for retinal degeneration. Low-vision aids and orientation and mobility training can help patients adapt to declining vision. Research into gene therapy and other molecular approaches is ongoing and represents a promising avenue for future treatment. Genetic counseling is recommended for affected individuals and their families.

Common questions about Usher syndrome type 3