In females carrying a CHM variant that abolishes the expression of one REP1 allele (i.e., deletion, frameshift, nonsense), the CHM mutated allele would not produce a final protein product; hence, Choroideremia manifestation would depend only upon XCI status of the wild type allele: the more cells presenting with inactivated wild type allele, the more involvement of the retina would occur. This evidence concerns the gene CHM and choroideremia.