WT1 and Nephroblastoma: The most common predisposition syndromes and their underlying genetic defect include WAGR syndrome (Wilms tumor, aniridia, genitourinary anomalies, and range of developmental delays) (WT1 deletion), Denys-Drash syndrome (WT1 mutation) and Beckwith-Wiedemann Syndrome (LOH or loss of imprinting (LOI) of 11p15).