Footnotes

• HC and JAL are joint last authors.

• Acknowledgements The authors thank the other members of the EUMYONET and Myositis Genetics Consortium (MYOGEN) for their scientific and logistic support. A full list of investigators who contributed to the UK MYONET (Adult Onset Myositis Immunogenetic Collaboration) and JDM study can be found in Miller FW et al.1 This study also makes use of data generated by the Wellcome Trust Case-Control Consortium. A full list of the investigators who contributed to the generation of the data is available from http://www.wtccc.org.uk. Funding for the project was provided by the Wellcome Trust under award 076113.

• Contributors MJ, HC, RGC and JAL were involved in the conception of the project. MJ, JM and JAL performed the methods and analysis of the project. The rest of the coauthors contributed samples for the purposes of the study, were involved in the discussion of final content and review/editing of the manuscript before submission.

• Funding This work was funded by Arthritis Research UK grant 18474, in part by the Intramural Research Program of the NIH, National Institute of Environmental Health Sciences, the European Science Foundation for EuMyoNet support and Association Francaise Contre Les Myopathies (AFM). The UK JDM Cohort and Biomarker study was supported by grants from the Wellcome Trust UK (085860), Action Medical Research UK, (SP4252), The Myositis Support Group UK, Arthritis Research UK (14518) and The Henry Smith Charity. The JDM Cohort study is adopted onto the Comprehensive Research Network through the Medicines for Children Research Network (http://www.mcrn.org.uk). The Czech cohort was supported by MH CZ-DRO Institute of Rheumatology 00023728.

• Competing interests None.

• Ethics approval Local ethics committees for each city.

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