RPGR and retinitis pigmentosa 1: Moreover, technical limitations, including the difficult amplification of RPGR ORF15, a mutational hotspot for X-linked RP, may have accounted for some of the missed diagnosis (our panel is presently covering only 30% of this critical exon), but the addition of the specific analysis by Sanger sequencing of the ORF15 of the RPGR gene in 10 males patients, with sporadic/X-linked RP and previously testing negative for pathogenic mutations using our NGS panel, did not reveal any mutation in the analyzed region.