To investigate the wider significance of NMD for expression of RAB23 transcripts, we used pyrosequencing to quantify the relative levels of wild-type and mutant transcripts in the mother of a patient who we previously reported with Carpenter syndrome (subject 3734; [Jenkins et al., 2007]), who was heterozygous for the c.434T>A (p.L145X) allele (Figure 3D). Here, RAB23 is linked to Carpenter syndrome.