Popliteal pterygium syndrome (PPS; MIM #119500), also results from mutations in IRF6 and has a similar orofacial phenotype to VWS but exhibits additional anomalies that include popliteal webbing, pterygia, oral synychiae, adhesions between the eyelids, syndactyly and genital anomalies (Bixler et al., 1973). This evidence concerns the gene IRF6 and van der Woude syndrome.