PITX1 and familial clubfoot with or without associated lower limb anomalies: Mutations at these genes can cause congenital limb deformities in humans, including clubfoot and Liebenberg syndrome (Pitx1; Gurnett et al., 2008; Spielmann et al., 2012), and Holt-Oram syndrome (Tbx5; Basson et al., 1997).