Footnotes

• Contributors The observations described in this communication were first made by JLT. MJH, SJ, NM and NMS contributed to developing the concept. NMS reviewed the background literature. SJ and NM produced the quoted data relating to the West of Scotland Genetics Service. MJH wrote the communication and subsequent revision in discussion with NM and SJ.

• Competing interests None.

• Patient consent Obtained.

• Provenance and peer review Not commissioned; externally peer reviewed.