The classical CFNS female phenotype is caused by heterozygous loss-of-function mutations in EFNB1 (MIM♯ 300035), which encodes the transmembrane signaling molecule ephrin-B1 [Twigg et al., 2004; Wieland et al., 2004]. The gene discussed is EFNB1; the disease is Craniofrontonasal dysplasia.