Footnotes

• Contributors SM and J-MV were responsible for medical literature analysis, with intellectual contribution from CG and LM. SM and J-MV drafted the article. All authors contributed to the conception and design of the paper, interpretation of data, critical revisions contributing to the intellectual content and approval of the final version of the manuscript.

• Competing interests None declared.

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

• Data sharing statement Data on the OMIM website at http://www.ncbi.nlm.nih.gov/Omim/mimstats.html