A novel mutation of the USH2C (GPR98) gene in an Iranian family with Usher syndrome type II

Usher syndrome (USH) is an autosomal recessive disease characterized by bilateral sensorineural hearing impairment (ARSNHL), and progressive visual loss due to retinitis pigmentosa (RP) with the present or absent of vestibular dys-function. USH is classied into three types based on the severity and progression of the clinical periods of the disease. Usher syndrome type 1 (USH1) which is manifested by severe to profound congenital hearing loss, vestibular dysfunction and prepubertal onset of RP is the most severe form of the USH (Millan et al. 2011; Le Quesne Stabej et al. 2012). Patients with Usher type 2, presented at the second decade of the life, are characterized by moderate to severe hearing loss (HL), normal vestibular function and RP. For Usher type 3 (USH3) clinically, postlingual progressive HL, RP and variable vestibular function are the most distinguished features (Dai et al. 2008; Millan et al. 2011; Le Quesne Stabej et al. 2012). Genetically, USH is highly heterogeneous (Dai et al. 2008). To date, underlying mutations in 15 loci and 11 genes have been identied to be responsible for USH.