Retinitis pigmentosa (RP) caused by sequence variants in the retinitis pigmentosa GTPase regulator gene (RPGR) constitute around three-quarters of all X-linked (XL) RP,1, 2, 3, 4 with RP2 variants predominantly accounting for the remaining cases.1, 3, 5, 6, 7 There is particular interest in RPGR-associated RP, and recently commenced gene therapy trials are underway (NCT03116113, NCT03252847, and NCT03316560). The gene discussed is RP2; the disease is retinitis pigmentosa 1.