USH2A and Hearing impairment: Usher Syndrome is classified into four main subtypes USH types I, II, III and IV; depending on the severity of hearing impairment, vestibular dysfunction, and the age at onset of retinitis pigmentosa (RP), which are further subclassified into 11 subtypes associated with an autosomal recessive mutation in a specific gene.1 The gene encoding Usher syndrome type IIA (USH2A) is located on chromosome 1q41 and spans 800 kb.