The spectrum of clinical variability of VWS has recently been expanded by the demonstration that mutations in IRF6 are also causative of the Popliteal Pterygium Syndrome (PPS; OMIM 119500), an allelic, autosomal dominant disorder that presents, besides the facial anomalies typical of VWS, bilateral popliteal webs, syndactyly, and genital anomalies [17]. Here, IRF6 is linked to popliteal pterygium syndrome.