Ten years after the publication of the diagnostic criteria for inclusion myositis, an international group of around thirty experts (including two from France) took part in the 272nd workshop of the European Neuromuscular Centre (ENMC) in June 2023 in the Netherlands. Their work resulted in:
- the inclusion of new diagnostic criteria, such as the finding of mitochondrial abnormalities on muscle biopsy, the presence of anti-cN1A autoantibodies or the existence of suggestive muscle images on MRI or ultrasound,
- a diagnostic approach that is now concluded in a binary way (inclusion myositis is confirmed or not confirmed), compared with three possibilities previously (probable, clinico-pathologically defined or clinically defined inclusion myositis).
The ENMC workshop also established a consensus on the design of clinical trials in inclusion myositis. In the light of past and current trials, it recommends in particular that:
- IBMFRS score as the primary endpoint,
- a duration of between 18 and 20 months for phases II/III, given the slow progression of the disease,
- a number of participants greater than 60 per treatment arm in a phase III controlled trial,
keeping an exercise diary and maintaining a stable level of physical activity during the clinical trials.
