RCAD caused by HNF1B mutations is also likely to be a disease of haploinsufficiency as whole gene deletions of HNF1B have been documented (Edghill et al. 2007), and a number of mutations in HNF4A have also been shown to be loss-of-function (Yang et al. 2000). The gene discussed is HNF1B; the disease is renal cysts and diabetes syndrome.