RPGR and retinitis pigmentosa 1: Thirty to 40% of RP cases can be attributed to an autosomal dominant mode of inheritance; 45% to 60%, to an autosomal recessive mode; and 5% to 15%, to an X-linked (XL) mode.1,6 In around 75% of cases, XLRP is caused by pathogenic sequence variants within the retinitis pigmentosa GTPase regulator gene (RPGR).