POU3F4 and deafness: Mutations in POU3F4 lead to mixed conductive and sensorineural X-linked DFN3/DFNX2 deafness (OMIM #304400) associated to stapes fixation, cochlear incomplete partition type 3, and perilymphatic gusher during stapedectomy, and can account for up to 0.5% of all cases of severe childhood hearing disorders [121].