RPGR and retinitis pigmentosa 1: X-linked recessive retinitis pigmentosa (XLRP) is considered one of the most severe forms of RP, accounting for approximately 6%–20% of all RP cases (Tsang and Sharma, 2018b), and 70% of XLRP is due to variants in the RPGR gene (Shu et al., 2012).