The Potocki-Shaffer syndrome (P11pDs or DEFECT11 syndrome) (OMIM 601224) is caused by deletions in 11p11.2-p12, including the EXT2 and ALX4 genes, and is characterized by patients having MO combined with Foramina Parietalia Permagna (FPP) (OMIM 168500), mental retardation and craniofacial dysotosis [20,21]. The gene discussed is ALX4; the disease is Potocki-Shaffer syndrome.