It is possible that the cause of RP in this patient is PDE6B, and the second mutation on the second allele was not identified by us due to several possible genetic events [35], 1) larger deletions or rearrangements that are not detectable by Sanger sequencing; (2) deep intronic mutations, which caused aberrant splicing, but were not examined in our study and (3) mutations in regulatory regions, which were not examined in our study. The gene discussed is PDE6B; the disease is retinitis pigmentosa 1.