To our knowledge, this is the first case of foveal hypoplasia in a BCM patient and of mild clinical affection in a female carrier caused by the concomitant effect of variants in <i>OPN1LW/OPN1MW</i> and <i>GPR143</i> genes, thus as the result of the simultaneous action of two independent genetic defects. This evidence concerns the gene GPR143 and blue cone monochromacy.