Table 1.

Key demographics and significant univariable associations of early clinical and laboratory features with disease course in patients with juvenile idiopathic inflammatory myopathies.

Variable	Number (%) or Median (interquartile range)			Overall p-value	Odds ratio [95% confidence interval]
	Monocyclic (n=88)	Polycyclic (n=86)	Chronic (n=191)		Chronic vs. Monocyclic	Polycyclic vs. Monocyclic	Chronic vs. Polycyclic
Demographics
Age at diagnosis, years	7.5 (4.7–12.5)	6.5 (4.6–11.8)	8.1 (5.6–11.6)	0.3	NA	NA	NA
Delay to diagnosis, months	3.0 (1.4–7.4)	4.0 (2.0–9.0)	4.3 (2.0–11.7)	0.2	NA	NA	NA
Female gender	60 (68)	65 (76)	140 (73)	0.5	NA	NA	NA
Race				0.1	NA	NA	NA
Caucasian	62 (71)	62 (72)	116 (61)
African American	10 (11)	9 (11)	39 (20)
Other	16 (18)	15 (17)	36 (19)
Clinical subgroup
Juvenile dermatomyositis	76 (86)	69 (80)	150 (79)	0.4	NA	NA	NA
Juvenile polymyositis	6 (7)	8 (9)	14 (7)
Juvenile connective tissue myositis*	6 (7)	9 (11)	27 (14)
Clinical features
Severe illness onset	23 (26)	16 (19)	73 (38)	0.003	1.7 [1.0–3.1]	NS	2.7 [1.4–5.0]
Photosensitivity‡	12 (15)	18 (24)	59 (34)	0.005	2.9 [1.5–5.8]	NS	NS
“V-sign” and/or “Shawl-sign” rashes†	9 (11)	6 (8)	38 (21)	0.008	2.2 [1.0–4.9]	NS	3.2 [1.3–8.0]
Contractures†	28 (32)	14 (17)	59 (35)	0.01	NS	0.4 [0.2–0.9]	2.6 [1.3–5.0]
Cuticular overgrowth ‡	7 (8)	14 (19)	38 (23)	0.02	3.2 [1.4–7.5]	NS	NS
Weight loss	28 (33)	14 (17)	63 (34)	0.02	NS	0.4 [0.2–0.9]	2.5 [1.3–4.7]
Palpitations	0 (0)	4 (5)	2 (1)	0.03	NS	NS	NS
Dyspnea at rest	4 (5)	1 (1)	17 (9)	0.03	NS	NS	8.5 [1.1–66.7]
Syncope	0 (0)	2 (2)	0 (0)	0.04	NA	NS	NS
Distal weakness†	37 (45)	20 (26)	69 (38)	0.05	NS	0.4 [0.2–0.9]	NS
Overall clinical symptom score [0–1]§	0.23 (0.14–0.31)	0.18 (0.12– 0.25)	0.23 (0.14–0.32)	0.01	NS	0.05 [0.0–0.8]	48 [4–556]
Laboratory features
Aldolase elevated‡	58 (79)	68 (94)	143 (87)	0.03	NS	4.4 [1.4–13.9]	NS
Any myositis-specific autoantibodies† || (not including anti-MDA5)	38 (45)	50 (63)	122 (69)	0.001	2.7 [1.6–4.7]	2.1 [1.1–3.8]	NS
Any myositis-specific autoantibodies (including anti-MDA5)‡ ||	47 (60)	53 (75)	132 (81)	0.002	2.9 [1.6–5.3]	NS	NS
Anti-p155/140 autoantibodies†	13 (15)	24 (30)	70 (40)	0.0004	3.6 [1.9–7.0]	2.3 [1.1–5.0]	NS
Any myositis-associated autoantibodies¶	6 (7)	12 (14)	35 (19)	0.03	3.2 [1.3–7.9]	NS	NS
Anti-Ro autoantibodies	1 (1)	4 (5)	19 (10)	0.01	10.0 [1.3–76.9]	NS	NS

^*Connective tissue diseases that were associated with myositis included: systemic lupus erythematosus (n=11), juvenile idiopathic arthritis (n=8), systemic sclerosis (n=7), localized scleroderma (n=5), insulin-dependent diabetes (n=3), psoriasis (n=2), Sjögren’s syndrome (n=2), eosinophilic fasciitis (n=2), discoid lupus (n=1), juvenile idiopathic arthritis and systemic lupus erythematosus (n=1).

^†5–10% missing data;

^‡10–15% missing data; otherwise: <5% missing data.

^§Odds ratio: per 0.01 increase in overall clinical symptom score.

^||Any myositis-specific autoantibodies included anti-p155/140 (present in n=107 patients), anti-MJ (n71), anti-MDA5 (n=56), anti-Jo1 (n=10), anti-PL-12 (n=5), anti-KS (n=1), anti-Mi-2 (n=10), and anti-SRP (n=6). Anti-PL-7, anti-OJ, anti-Zo, anti-EJ, and anti-Ha autoantibodies were also tested, but were not observed.

^¶Any myositis-associated autoantibodies included anti-Ro (n=24), anti-U1-RNP (n=19), anti-U2-RNP (n=1), anti-U5-RNP (n=1), anti-PM-Scl (n=11), anti-Sm (n=4), anti-La (n=3), anti-Ku (n=2), anti-Th (n=1), anti-SUMO (n=1), and anti-TMG cap (n=1) autoantibodies. Anti-U3-RNP and anti-U4-RNP were also tested, but were not observed. The sera from 81 patients had no identified myositis-specific (including anti-MDA5 autoantibodies) or -associated autoantibodies.

NA: Not applicable; NS: not significant (i.e. p≥0.05).