Table 2: Clinical characteristics of patients with IIM.

Variable Group
Group 1
(n=28)
Group 2
(n=9)
Group 3
(n=5)
Group 4
(n=53)
p-value
Female, n (%) 19 (67.9) 6 (66.7) 4 (80) 45 (84.9) 0.221
Age at the time of biopsy (years) 50.6±1.6 48.0±13.3 54.6±10.9 44.9±13.2 0.140
Disease duration (months) 2.1 (1.1, 3.2) 1.9 (1.1, 3.9) 0.7 (0.1, 4.6) 0.9 (0.3, 2.1) 0.005**
Corticosteroid (CS) used before biopsy; (N=25), n (%) 5 (17.9) 1 (11.1) 1 (20.0) 18 (34.0) 0.329
Current dose of CS, mg 60 (30,60) 50 2.5 12.5 (5, 37.5) 0.075
Immunosuppressive used before biopsy; (N=13), n (%) 2 (7.1)a 1 (11.1)a 1 (20.0)b 9 (16.9)c 0.512
Myalgia, n (%) 11 (39.3) 3 (33.3) 2 (40.0) 22 (41.5) 0.982
Arthritis, n (%) 3 (10.7) 1 (11.1) 0 11 (20.8) 0.626
Dysphagia, n (%) 5 (17.9) 2 (22.2) 1 (20.0) 11 (20.8) 1.000
Cardiac involvement, n (%) 1 (3.6)d 0 0 13 (24.5)e 0.034
Pulmonary involvement, n (%) 6 (21.4)f 0 0 15 (28.3)g 0.197
Muscle power
Prior CS, (N=70) 3.1±0.8(n=23) 3.2±0.7(n=8) 2.9±0.5(n=4) 3.6±0.6(n=35) 0.050
After CS, (N=25) 2.9±0.7(n=5) 3.0(n=1) 3.5(n=1) 3.8±0.6(n=18) 0.450
CK (mg/dl)
Prior CS, (N=70) 7,098(4,086, 10,857) (n=23) 2,215.5 (379.7, 4,238) (n=8) 1,605.5 (424.7, 2,646.7) (n=4) 1,440.0 (666, 2,381) (n=35) <0.001**
After CS, (N=25) 1,482 (693, 5,865) (n=5) 293.0(n=1) 279.0(n=1) 2,278 (472.5, 4,435) (n=18) 0.299
ESR (mm/hr), (n=64)
Prior CS, (N=44) 60.0 (37.0, 77.0)
(n=11)
46.0 (8.5, 64.0)
(n=5)
48.0 (33.0, 63.0)
(n=2)
76.5 (54.2, 94.7)
(n=26)
0.299
After CS, (N=20) 13.0 (10.5,20.0)
(n=4)
(n=0) (n=0) 87.0 (28.7, 100.2)
(n=16)
0.008**

Group 1 = idiopathic PM, group 2 = idiopathic DM, group 3 = PM/DM associated with malignancy, and group 4 = PM/DM associated with CTD.
Parametric continuous variables presented as mean±SD; non-parametric variables presented as IQR (Q1, Q3);
Categorical variables, parametric continuous variables and non-parametric continuous variables in the four groups of patients were compared using the Fisher’s exact test, one-way analysis of variance, and Kruskal-Wallis test, respectively.
**p<0.01
Prior CS=underwent biopsy prior using corticosteroid; After CS= underwent biopsy after using corticosteroid
Immunosuppressive treatment: a = methotrexate; b = azathioprine; c = methotrexate (n=5), cyclophosphamide (n=1), d-penicillamine (n=1), leflunomide (n=1), and mycophenolate mofetil (n=1).
Cardiac involvement: d=1 myocarditis; e= 4 myocarditis, 8 mild to moderate pericardial effusion in, and 6 PAH
Pulmonary involvement: f=5 ILD and 1respiratory muscle weakness; g= 13 ILD, 1 pleural effusion and 1 respiratory muscle weakness.