Background Arthritis is frequently observed symptom in patients with idiopathic inflammatory myopathies (IIM) in clinical practice, but there is a lack of systematic reports of prevalence and/or characteristics of arthritis in myositis patients.
Objectives To determine prevalence of arthritis in IIM patients; it’s relation to the course of the muscle disease; characteristics of arthritis with respect to severity, distribution and extent as well as it’s relation to autoantibody profiles, HLA genes, and others disease’s characteristics.
Methods 106 consecutive patients with definite diagnosis of IIM were included in this cross-sectional study. 68-joint index and clinical aspects of disease, history of arthritis and autoantibody profiles were obtained. Musculoskeletal ultrasonography using German Ultrasound Score 7 (US-7) was performed in 55 IIM patients and in 60 control patients with rheumatoid arthritis (RA). High resolution genotyping in HLA-DRB1 locus was performed in 71 IIM patients.
Results In 65 patients (61.3%) arthritis occurred at any time during the course of myositis; 42 had arthritis at the beginning of myositis (in 22 patients before and in 16 simultaneously with onset of muscle weakness). On clinical examination 52 (49.1%) patients had arthritis, with 25 having polyarthritis, 17 oligoarthritis and 10 monoarthritis. Wrists (21.7%) and shoulders, MCP, and PIP joints (each 20.8%) were the most frequently affected joints. Significant association of Anti-Jo-1 positivity with arthritis was found (28 patients with arthritis from 29 anti-Jo-1 positive; p<0.0001). Gray-Scale (GS) synovitis was observed in 39 out of 55 (70.9%) patients; Power-Doppler (PD) activity was present in 34 (61.8%). Only 4 (7.3%) patients had US tenosynovitis and 3 (5.5%) had bony erosions. 57/60 (95%) RA patients had GS-synovitis, which was PD-active in 54 (90%). In the control group of RA patients tenosynovitis was present in 25 (41.7%) patients and 25 (41.7%) patients had one or more joint erosions. Mean US-7 score as well as scores of individual joints or modality subscores were significantly lower in IIM than in RA. When only patients with positive findings were compared, significant differences were found in total US-7 score, and GS-synovitis and PD-tenosynovitis subscores, but not in PD-synovitis, GS-tenosynovitis as well as in scores of individual joints. No association of arthritis and HLA-DRB1 was found.
Conclusions Our data suggest that arthritis is a common feature of myositis. It is often present at the beginning of muscular manifestation of disease, or it may even precede the onset of muscle weakness. Most common presentation is symmetrical, non erosive polyarthritis affecting particularly wrists, shoulders, MCP and PIP joints of the hands. We confirmed strong association of arthritis with anti-Jo-1 antibody. Ultrasound assessment of joint involvement shows less frequent involvement than in RA, but comparable activity of synovitis measured by PD in affected joints. Patients with IIM have less erosions and tenosynovitis than RA patients.
Backhaus M, Ohrndorf S, Kellner H et al. Evaluation of a novel 7-joint ultrasound score in daily rheumatologic practice: a pilot project. Arthritis Rheum. 2009;61:1194-201.
Acknowledgements Supported by the project (Ministry of Health, Czech Republic) for conceptual development of research organization 00023728 (Institute of Rheumatology) and Research grant (Ministry of Health, Czech Republic) NT 12437
Disclosure of Interest None Declared