Usher syndrome type 2

Usher syndrome type 2 (USH2) is an autosomal recessive genetic disorder characterized by the combination of congenital sensorineural hearing loss and progressive retinitis pigmentosa (RP). It is the most common form of Usher syndrome, accounting for more than half of all cases. Unlike Usher syndrome type 1, individuals with type 2 are born with moderate-to-severe hearing loss (rather than profound deafness) and do not typically experience vestibular (balance) dysfunction. Hearing loss is present from birth and is generally stable or slowly progressive, predominantly affecting higher frequencies. Vision problems due to retinitis pigmentosa usually become apparent during adolescence or early adulthood, beginning with night blindness and progressive loss of peripheral vision, which can eventually lead to significant visual impairment or legal blindness. The most commonly implicated gene is USH2A, which encodes the protein usherin, important for the structure and function of both photoreceptor cells in the retina and hair cells in the inner ear. Other genes associated with USH2 include ADGRV1 (formerly GPR98 or VLGR1) and WHRN (encoding whirlin). Diagnosis is based on clinical findings of bilateral sensorineural hearing loss with retinitis pigmentosa, audiometric testing, electroretinography (ERG), and can be confirmed through molecular genetic testing. There is currently no cure for Usher syndrome type 2. Management is multidisciplinary and focuses on optimizing hearing through hearing aids, which are typically effective given the moderate-to-severe nature of the hearing loss. Ophthalmologic care includes regular monitoring of retinal function, low-vision aids, and orientation and mobility training as vision declines. Cochlear implants may be considered in cases of progressive hearing loss. Research into gene therapy, particularly targeting USH2A, is actively underway and represents a promising future therapeutic avenue. Genetic counseling is recommended for affected individuals and their families.

Common questions about Usher syndrome type 2