Arthritis in Idiopathic Inflammatory Myopathies

Arthritis is a well-recognized symptom of idiopathic inflammatory myopathies (IIM). We provide a summary of available data regarding the epidemiology, clinical characteristics, and autoantibody associations of joint involvement in various forms of IIM.

Arthritis is reported in 18-55% of patients with IIM. It is particularly frequent (20-70%) in those with antisynthetase syndrome (ASS); highest prevalence is associated with anti-Jo-1 positivity. Most common manifestation is non-erosive polyarthritis. X-ray erosions may be found occasionally in ASS, particularly in patients with overlap with rheumatoid arthritis (RA). Arthritis is often present at the time of IIM diagnosis and it may even precede the onset of muscle weakness. Arthritis may in some cases be the main disease manifestation responsible for the disease burden in patients with IIM. Arthritis is a frequent symptom of IIM. Polyarthritis of small joints of the hands is the most frequent clinical manifestation. Arthritis may be the first or dominant symptom in IIM and therefore patients may be initially misdiagnosed as having RA. Particularly in seronegative RA patients with interstitial lung disease or Raynaud's phenomenon, the possibility of IIM should be considered.