Heterozygous intragenic, dominant-negative mutations in WT1 have been identified in several overlapping developmental disorders characterised by Wilms tumour, genital malformations, male-to-female sex reversal, nephropathy, diaphragmatic hernia and gonadoblastoma (Pelletier et al. 1991; Hastie 1992). Here, WT1 is linked to Wilms tumor.