IRF6 and van der Woude syndrome: Mutations in IRF6 are linked to Van der Woude Syndrome (VWS, OMIM 119300), Popliteal Pterygium Syndrome (PPS, OMIM 119500), and non-syndromic orofacial cleft lip (CL/P, OMIM 119530) [34], [35], [36], ].