Pre-HSCT %DHR + was 10% and genetic analysis identified a large heterozygous deletion (Xp.21.1p.11.4) encompassing CYBB along with OTC (ornithine transcarbamylase, implicated in hyperammonaemia [24]), RPGR (retinitis pigmentosa GTPase regulator, implicated in retinitis pigmentosa [25]), XK (X-linked Kx blood group antigen, Kell and VPS13A binding protein, implicated in development of McLeod syndrome [26]), and TSPAN7 (tetraspanin-7, implicated in X-linked intellectual disability [27]). Here, OTC is linked to retinitis pigmentosa.