Chromosomal aberrations such as deletions, translocations, and inversions encompassing the complete PAX6 gene or a part of the PAX6 gene may lead to isolated aniridia or severe WAGR syndrome, which is characterized by Wilms tumor, aniridia, genital malformations, and intellectual disability due to a large deletion on the 11p13 region encompassing the PAX6 gene and its adjacent WT1 gene. The gene discussed is PAX6; the disease is WAGR syndrome.