SNRPB and cerebrocostomandibular syndrome: Since none of the other patients carry truncating mutations in the gene (which would be much more likely to occur by chance than point mutations at two specific loci), and truncating mutations in or deletions encompassing SNRPB have not been reported23, 24, we suggest that SNRPB haploinsufficiency may cause a more severe and likely lethal phenotype that is distinct from classic CCMS.