Usher syndrome is a rare genetic disease that affects both hearing and vision. It causes deafness or progressive hearing loss and retinitis pigmentosa (RP) at the ocular level. This disease would be responsible for approximately half of the cases of deafblindness in those under age 65.
Clinical heterogeneity is wide, but three main types of the disease are established:
- Usher syndrome type I: characterized by profound congenital bilateral sensorineural deafness, absence of vestibular function, and prepubertal onset of RP.
- Usher syndrome type II: congenital deafness is moderate-severe and vestibular function is normal. The appearance of RP usually occurs at the end of the second decade or the beginning of the third.
- Usher syndrome type III: deafness is progressive and postlingual, vestibular dysfunction is variable, and progressive RP has a variable age of onset.