In France, the National Data Bank for Rare Diseases lists 1,156 patients followed up in Centres of Reference or Competence for an anti-synthetase syndrome (SAS), an entity associated with overlapping myositis, which until now has lacked a consensual definition.
The members of the international project Classification Criteria for Anti-synthetase Syndrome (Class) :
- have identified clinical and serological features more specific to SAS (arthritis, diffuse myalgias, interstitial pneumopathy, etc.) and others that do not differentiate SAS (isolated presence of joint pain, difficulty swallowing, myocarditis, etc.) by analysing data from 948 patients with this syndrome and 1,077 control patients,
- This work, funded by rheumatology learned societies (EULAR/ACR), should continue, leading to the publication of shared classification criteria, validated on the basis of the project data.
Furthermore, in November 2023, a workshop of the European neuromuscular centre (ENMC) :
- produced clinical and biological criteria for ‘probable’ SAS and ‘definite’ SAS (reliable anti-synthetase autoantibody positivity associated with at least one interstitial lung disease, myositis or arthritis),
- emphasised that not only the presence of anti-synthetase autoantibodies, but also their method of detection (immunoprecipitation, Elisa, commercial immunoblot) play a central role in the diagnostic process, the complete clinical triad of myositis – arthritis – interstitial lung disease, classically described, being inconstant (20 to 50% of patients after six years’ follow-up).
The 21 experts from nine countries, including France, brought together by the ENMC have also produced a decision-making algorithm for treatment, based on the severity of the clinical picture and how quickly it develops.
