Table 1

Clinical characteristics of patients with an inflammatory myopathy and controls

CharacteristicsIIMControls
n9572
Age (years)*62.3 (52.3–71.3)54.5 (45.0–72.4)
Female:male ratio2.71.3
Symptom duration time (months)*4.0 (2.0–10.0)7.0 (1.5–24.0)
Proximal muscle weakness76.8%47.2%
Dysphagia26.3%9.7%
Elevated muscle enzymes83.2%69.4%
Myopathic EMG67.8% (61/90)36.5% (23/63)
Skin involvement53.7%1.4%
Interstitial lung disease36.8%4.2%
Arthritis24.2%2.8%
Raynaud phenomenon21.1%4.2%
MSA and/or MAA†58.9%0%
Anti-Jo-116.8%0%
HEP-2 titre ≥1:8061.1%9.7%
Muscle biopsy done91.6%100%
Muscle biopsy positive97.7%0%
Clinical diagnosis
  Dermatomyositis27.1%
  Antisynthetase syndrome22.1%
 Immune-mediated necrotising myopathy14.7%
  Myositis overlap syndrome14.7%
  Polymyositis10.5%
  Cancer-associated myositis7.4%
  Inclusion body myositis1.1%
  Unspecified myositis2.1%
  • *Median (IQR).

  • †MSA (myositis- specific antibodies) or MAA (myositis-associated antibodies): anti-Jo-1, anti-PL7, anti-PL12, anti-Mi-2, anti-SRP, anti-HMGCR, anti-MDA5; anti-TIF1γ; anti-NXP-2; anti-SAE; anti-Ku; anti-PM-Scl; anti-Ro; anti-U1RNP; anti-Scl-70.

  • EMG, electromyography; IIM, idiopathic inflammatory myopathies.