MYO7A mutation screening in Usher syndrome type I patients from diverse origins

Abstract
Phenotypically, three clinical types of Usher syndrome have been defined according to the severity of hearing impairment, age of retinitis pigmentosa onset and the presence or absence of vestibular response. Usher syndrome type I (USH1) is the most serious type, characterised by severe to profound congenital sensorineural hearing loss, balance deficiency and prepubertal onset of retinitis pigmentosa leading to blindness. USH2 is characterised by moderate to severe hearing impairment, normal vestibular function and later onset of retinal degeneration than USH1. USH3 displays progressive hearing loss, retinitis pigmentosa and variable vestibular phenotype.