SNRPB and cerebrocostomandibular syndrome: Here we present mutations in a highly conserved, alternative PTC-containing exon of the small nuclear ribonucleoprotein polypeptides B and B1 (SNRPB) gene (Fig. 1) as the cause of cerebro–costo–mandibular syndrome (CCMS), a human multiple malformation disorder characterized by posterior rib gaps and Pierre Robin sequence (micrognathia, glossoptosis and cleft palate).