This disorder is caused by mutations in the WT1 gene and so is allelic with Denys–Drash syndrome. It is characterized by male pseudohermaphroditism, streak gonads, and steroid-resistant nephritic syndrome and renal failure from focal and segmental glomerulosclerosis, but although gonadoblastoma is frequent, the risk of Wilms Tumours is much less, and the glomerulopathy progresses more slowly than in Denys–Drash syndrome. The risk of Wilms Tumours has been estimated at 5–10 % risk, and affected children should also be offered surveillance by 3–4-monthly renal ultrasonography (Scott et al. 2006). The WT1 intron 9 splicing mutations that cause Frasier syndrome alter the balance of WT1 isoforms (Klamt et al. 1998) and cause Frasier syndrome if the karyotype is 46,XY and isolated nephrotic syndrome if the karyotype is 46,XX (Chernin et al. 2010).