Ten patients suffered from congenital malformations of the craniocervical junction: three in Down syndrome (with os odontoideum in one), two patients diagnosed with spondyloepiphyseal dysplasia congenital (SED), and the other patients were diagnosed with Larsen syndrome (n = 1), Marfan syndrome (n = 1), Arnold Chiari syndrome type 2 (n = 1), a syndrome caused by a de novo mutation in ZMYND11 [6] (n = 1), and a syndrome of unknown origin (n = 1). Here, ZMYND11 is linked to Down syndrome.