Footnotes

• Handling editor Josef S Smolen

• Contributors All authors contributed to information gathering, compiling, writing, editing and reviewing the manuscript. FWM is the guarantor.

• Funding This research was supported by the Intramural Research Programs of the NIH, National Institute of Environmental Health Sciences, National Institute of Arthritis and Musculoskeletal and Skin Diseases, and National Human Genome Research Institute.

• Competing interests None declared.

• Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

• Provenance and peer review Commissioned; externally peer reviewed.