IRF6 mutations, in addition to causing Van der Woude syndrome, can cause popliteal pterygium syndrome, an autosomal dominant disorder characterized by orofacial anomalies including lower lip pits, cleft lip and/or palate, syngnathia, syndactyly, webbing of the lower limbs, and genital abnormalities [87]. The gene discussed is IRF6; the disease is van der Woude syndrome.