Synpolydactyly (SPD) is a dominantly inherited congenital limb malformation showing digit duplication and webbing of third and fourth fingers. Mutation in HOXD13 induces synpolydactyly. Synpolydactyly 2 is associated with metacarpal and metatarsal synostoses. Synpolydactyly 2 is very rare and caused by mutations in FBLN1.