Combination of retinitis pigmentosa and hearing loss caused by a novel mutation in PRPH2 and a known mutation in GJB2: importance for differential diagnosis of Usher syndrome.
A total of 133 children from two deaf and hard of hearing pediatric populations were genotyped first for GJB2/6 and, if negative, then for Usher syndrome.
This is illustrated by three different examples: (1) the DFNB9 deafness form, a synaptopathy of the cochlear sensory cells where otoferlin is defective; (2) the Usher syndrome, in which deafness is related to abnormal development of the hair bundle, the mechanoreceptive structure of the sensory cells to sound; (3) the DFNB1 deafness form, which is the most common form of inherited deafness in Caucasian populations, mainly caused by connexin-26 defects that alter gap junction communication between nonsensory cochlear cells.