Genetic homogeneity and phenotypic variability among Ashkenazi Jews with Usher syndrome type III

sher syndrome (USH) is an autosomal recessive disorder comprising of bilateral sensorineural hearing loss, progressive loss of vision due to retinitis pigmentosa (RP), and variable vestibular dysfunction. It is the most frequent cause of deafness and concurrent blindness in schools for the deaf-blind, 1 with a prevalence of 1/16 000 to 1/ 50 000 in various populations. The majority of Usher syndrome cases can be clinically classified into three subtypes. 3 4 USH type I (USH1; OMIM 276900, 276903, 276904, 601067, 602097, 602083 and 606943) is characterised by profound prelingual sensorineural hearing loss, vestibular areflexia, and prepubertal onset of RP. USH type II (USH2; OMIM 276901, 276905 and 605472) is characterised by moderate to severe hearing impairment, no vestibular impairment, and onset of RP in the first or second decade of life. USH type III (USH3; OMIM 276902) is characterised by progressive, post-lingual hearing loss, variable onset and severity of RP, with or without vestibular dysfunction. 6]