TNFSF15 and Hearing impairment: We searched for mutations in the regions corresponding to the hotspots for deafness: the MT-RNR1 and the MT-TS1 genes, as the presence of mutations in these two genes in particular, is known to cause both syndromic and non-syndromic forms of hearing impairment; we also focused on the region of MT-TL1 as previous studies report its possible role in non-syndromic disease (29).