Table 1 Characteristics of the 100 patients with inflammatory myopathy with anti-SRP antibody

Females/males

61/39

Age at diseases onset

 Mean ± SD

51.3 ± 19.3

 Age ≤ 15 years

8

Antecedent infection

7

Statin-exposure

5

Duration from the disease onset to the first examination

 ≤12 months

77

 >12 months

23

Initial symptoms

 Arms

19

 Legs

67

 Bulbar

7

 Trunk

7

Muscle weakness

 Legs predominantly than arms

69

 Severe limbs weakness

63

 Laterality

16

 Distal muscle dominant

3

 Neck weakness

70

 Dysphagia

41

 Facial muscle involvement

10

 Cardiac muscle involvement

2

 Decreased capacity of respiratory function

12

Muscle atrophy

66

Scapular winging

10

Decreased deep tendon reflex

51

Myalgia

34

Extramuscular symptoms

 Fever

8

 Skin rash

6

 Arthritis

4

 Raynaud phenomenon

7

 Interstitial lung disease

13

Associated disorder

 Cancer

5

 Rheumatic disease

9

Blood examination

 Creatine kinase (IU/L, mean ± SD)

6161 ± 4725

 Elevated C-reactive protein

17

 Antinuclear antibody positivity

5

Electromyography

 Spontaneous activity

41/86 (48 %)

 Low-amplitude, short-duration motor unit potentials

79/86 (92 %)

Muscle images

 Atrophy on CT or MRI

46/79 (58 %)

 Increased signals on T2 or STIR images

49/58 (84 %)

Histological diagnosis

 Necrotizing myopathy

84

 Sporadic inclusion body myositis

0

 Polymyositis

1

 Dermatomyositis

1

 Non-specific myositis

14

Autoantibodies

 7S RNA of SRP

100

 54-kD protein of SRP

82

 3-hydroxyl-3-methylglutatyl-coenzyme A reductase

3

 Aminoacyl transfer RNA synthetase

0