Idiopathic inflammatory myopathies and antisynthetase syndrome: contribution of antisynthetase antibodies to improve current classification criteria

The presence of muscle weakness and anti-Jo1 anti-aminoacyl transfer RNA synthetase (ARS) autoantibodies are evaluated in the new European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) proposed classification criteria for adult and juvenile idiopathic inflammatory myopathies (IIM), as well as in the Solomon proposed criteria for antisynthetase syndrome (ASSD) diagnosis.1 2 That favours an overlapping in both criteria fulfilment; however, ASSD is not considered among the IIM subgroups classification. Anti-Jo1 ARS positivity is the highest weighted criterion in the EULAR/ACR criteria. Furthermore, anti-PL7 and anti-PL12 ARS were found to be strongly associated with IIM during the criteria development; however, the low number of observations limited their reliability analysis, and they were not finally included.1 3 Anti-EJ, anti-OJ and other ARS were not considered at all due to the limited availability of detection methods at the start of the criteria development.3 On the other hand, any ARS positivity is considered in Solomon’s criteria. Thus, according to other authors, we purpose that IIM and ASSD classification criteria …