In humans, rare IRF6 variants are causal for Van der Woude syndrome (VWS, OMIM: 119300) and Popliteal Pterygium syndrome (PPS, OMIM: 119500), which are characterized by the presence of orofacial clefts, lip pits as well as cutaneous and limb defects. The gene discussed is IRF6; the disease is popliteal pterygium syndrome.