ES identified a heterozygous mutation (c.325C>T; p.Arg109Cys) in the X-linked EFNB1 (ephrin-B1) gene, previously reported in a patient with craniofrontonasal syndrome (CFNS).38 Dideoxy sequencing of the parents showed that the clinically unaffected father (I-1) was hemizygous for the same variant (figure 1B). The gene discussed is EFNB1; the disease is Craniofrontonasal dysplasia.