CYP26A1 and blindness (disorder): Interestingly, deletions involving the 5' portion of the EXOC6A gene and two adjacent cytochrome p450 genes (CYP26A1 and CYP26C1) are associated with autosomal-dominant nonsyndromic optic aplasia (ONA), an extremely rare disorder that causes unilateral or bilateral blindness in the affected eye (Meire et al., 2011).