Usher syndrome type I is an autosomal recessive condition characterized by profound congenital hearing impairment with unintelligible speech, early retinitis pigmentosa (usually evident within the first decade), and constant vestibular dysfunction. Type I is distinguished from type II on the basis of severity of hearing loss and the extent of vestibular involvement. Type I patients are profoundly deaf, and have defective vestibular function. Usher syndrome type ID (USH1D) is caused by homozygous or compound heterozygous mutation in the gene encoding cadherin-23. [From OMIM]