These include Opitz B/GGG syndrome [OMIM 300000], due to mutations in MID1 [OMIM 300552] at Xp22.3 [42], in which laryngeal malformations (cleft, diastema) are more usual; McKusick–Kaufman syndrome [OMIM 236700], which is allelic with Bardet–Biedl syndrome [BBS-6, OMIM 209900] and due to mutations in MKKS [OMIM 604896] [51,53], a gene related to members of the chaperonin family; and Oculo-Auriculo-Vertebral Spectrum [OAVS, OMIM 164210], for which epigenetic dysregulation of BPAX1 has been proposed as an aetiological mechanism [14]. The gene discussed is MKKS; the disease is Bardet-Biedl syndrome.