Clinical and serological features at IIM diagnosis of the overall IIMs population categorised as not associated ILD (IIMs not-ILD) and IIMs-associated ILD (IIMs-ILD)
| Overall population (n=253) | IIMs non-ILD (n=128) | IIMs-ILD (n=125) | P value | |
| Demographics | ||||
| Female—n (%) | 183 (72) | 94 (73) | 89 (71) | 0.69 |
| Age at diagnosis—years | 55 (46–66) | 54 (41–67) | 57 (49–66) | 0.056 |
| History of cancer—n (%) | 37 (15) | 20 (16) | 17 (14) | 0.64 |
| Follow-up duration—years | 6 (3–10) | 6 (3–10) | 5 (3–9) | 0.44 |
| IIM clinical phenotype | ||||
| Polymyositis—n (%) | 67 (27) | 41 (32) | 26 (21) | 0.047 |
| Dermatomyositis—n (%) | 96 (38) | 67 (52) | 29 (23) | <0.0001 |
| Inclusion body myositis—n (%) | 5 (2) | 5 (4) | 0 (0) | 0.06 |
| Necrotising autoimmune myopathy—n (%) | 8 (3) | 8 (6) | 0 (0) | 0.007 |
| Anti-synthetase Syndrome—n (%) | 77 (30) | 7 (5) | 70 (56) | <0.0001 |
| Clinical features | ||||
| Arthralgia—n (%) | 128 (51) | 53 (41) | 75 (60) | 0.003 |
| Arthritis—n (%) | 53 (21) | 15 (12) | 38 (30) | 0.0003 |
| Muscular weakness—n (%) | 171 (68) | 99 (77) | 72 (58) | 0.001 |
| Fever—n (%) | 48 (19) | 15 (12) | 33 (26) | 0.004 |
| Fatigue—n (%) | 119 (47) | 60 (47) | 59 (47) | 0.99 |
| Heliotropic rash—n (%) | 74 (29) | 56 (44) | 18 (14) | <0.0001 |
| Gottron’s papules—n (%) | 40 (16) | 23 (18) | 17 (14) | 0.39 |
| Gottron’s sign—n (%) | 37 (15) | 24 (19) | 13 (10) | 0.08 |
| Mechanic’s hands—n (%) | 30 (12) | 4 (3) | 26 (21) | <0.0001 |
| Raynaud’s phenomenon—n (%) | 47 (19) | 16 (13) | 31 (25) | 0.02 |
| Dysphonia—n (%) | 9 (4) | 3 (2) | 6 (5) | 0.33 |
| Dysphagia—n (%) | 58 (23) | 42 (33) | 16 (13) | 0.0002 |
| Xerostomia—n (%) | 23 (9) | 9 (7) | 14 (11) | 0.28 |
| Xerophthalmia—n (%) | 21 (8) | 8 (6) | 13 (10) | 0.26 |
| Dyspnoea—n (%) | 68 (27) | 8 (6) | 60 (48) | <0.0001 |
| Cough—n (%) | 26 (10) | 2 (1) | 24 (19) | <0.0001 |
| Muscle involvement | ||||
| MMT-8 at diagnosis | 140 (120–150) | 133.5 (112–148) | 148 (130–150) | <0.0001 |
| CK at diagnosis—U/L | 674 (128–3268) | 1264 (173–4960) | 433 (100–2255) | 0.001 |
| Muscle biopsy—n (%) | 108 (43) | 70 (55) | 38 (30) | <0.0001 |
| Muscle biopsy abnormalities—n (%) | 95 (38) | 62 (48) | 33 (26) | <0.0001 |
| MRI—n (%) | 109 (43) | 65 (51) | 44 (35) | 0.01 |
| MRI abnormalities—n (%) | 96 (40) | 63 (49) | 33 (26) | 0.0002 |
| Autoantibody profile | ||||
| Antinuclear antibodies—n (%) | 162 (64) | 74 (58) | 88 (70) | 0.049 |
| Myositis-specific antibodies—n (%) | 138 (55) | 51 (40) | 87 (70) | <0.0001 |
| Myositis-associated antibodies—n (%) | 120 (47) | 47 (37) | 73 (58) | 0.0003 |
| Anti-synthetase—n (%) | 87 (34) | 12 (9) | 75 (60) | <0.0001 |
| Anti-Jo-1—n (%) | 63 (25) | 7 (5) | 56 (45) | <0.0001 |
| Anti-PL12—n (%) | 13 (5) | 4 (3) | 9 (7) | 0.14 |
| Anti-PL7—n (%) | 14 (6) | 6 (5) | 8 (6) | 0.55 |
| Anti-PM/Scl—n (%) | 29 (11) | 12 (9) | 17 (14) | 0.29 |
| Anti-SSA/Ro—n (%) | 80 (32) | 23 (18) | 57 (46) | <0.0001 |
| Anti-SSB/La—n (%) | 10 (4) | 6 (5) | 4 (3) | 0.54 |
| Anti-U1RNP—n (%) | 9 (3) | 6 (5) | 3 (2) | 0.33 |
| Anti-Mi2—n (%) | 21 (8) | 17 (13) | 4 (3) | 0.005 |
| Anti-Ku—n (%) | 9 (3) | 4 (3) | 5 (4) | 0.71 |
| Anti-TIF1γ—n (%) | 7 (3) | 6 (5) | 1 (1) | 0.12 |
| Anti-Ro52—n (%) | 44 (17) | 11 (8) | 33 (26) | 0.0002 |
| Anti-MDA5—n (%) | 10 (4) | 1 (1) | 9 (7) | 0.01 |
| Anti-EJ—n (%) | 4 (1.5) | 1 (1) | 3 (2) | 0.37 |
| Anti-SRP—n (%) | 16 (6) | 12 (9) | 4 (3) | 0.07 |
| Anti-SAE1—n (%) | 3 (1) | 3 (2) | 0 | 0.25 |
| Treatment | ||||
| Glucocorticoids—n (%) | 236 (93) | 119 (93) | 117 (94) | 0.84 |
| Dose at treatment initiation—mg | 25 (0–500) | 37.5 (5–500) | 25 (0–75) | 0.01 |
| Methotrexate—n (%) | 155 (61) | 104 (81) | 51 (41) | <0.0001 |
| Mycophenolate mofetil—n (%) | 78 (31) | 15 (12) | 63 (50) | <0.0001 |
| Azathioprine—n (%) | 41 (16) | 11 (9) | 30 (24) | 0.0009 |
| Cyclophosphamide—n (%) | 17 (7) | 2 (1) | 15 (12) | 0.0008 |
| Rituximab—n (%) | 56 (22) | 17 (13) | 39 (31) | 0.0007 |
| Intravenous immunoglobulin—n (%) | 61 (24) | 39 (30) | 22 (18) | 0.02 |
Values are expressed as numbers and (%) or median and ranges, as appropriate.
CK, creatine kinase; IIMs, idiopathic inflammatory myopathies; ILD, interstitial lung disease; MDA5, anti-melanoma differentiation-associated gene; MMT, manual muscle test; SAE, small ubiquitin-like modifier-1 activating enzyme; SRP, signal recognition particle; TIF1γ, transcription intermediary factor 1-gamma.