Takeaway
People positive for the anti-melanoma differentiation-associated gene 5 antibody (anti-MDA5+) are a distinct group from people with myositis, and have a systemic syndrome composed of 3 different entities with different prognoses.
Why this matters
The finding underlies the importance of anti-MDA5 antibody screening in people with seronegative polyarthritis and people with interstitial pneumonia, with a suspicion of autoimmune features.