WT1 and Wilms tumor: Aniridia may occur either as an isolated ocular abnormality without systemic involvement, caused by mutations in the Paired Box gene 6 (PAX6) located on chromosome 11p13, or as a part of the Wilms tumor-aniridia-genital anomalies-retardation (WAGR) syndrome (OMIM,194072), caused by deletion of a region of chromosome 11p13-p12 containing both the Wilms tumor 1 (WT1) and PAX6 genes.