Anti-MDA5 autoantibodies in juvenile dermatomyositis identify a distinct clinical phenotype: a prospective cohort study

Table 1 Demographic characteristics of the 285 patients in this study

	All JDM patients, n = 285	Anti-MDA5-positive patients, n = 21
Female, number (%)	206 (72)	15 (71)
Caucasian, number (%)	220 (78)	16 (76)^b
Diagnosis, number (%) ^a
Dermatomyositis	242 (85)	21 (100)
Polymyositis	1 (0.4)	0
Overlap	33 (12)	0
Age at disease onset, years, median (IQR)	6.3 (IQR 4 to 10)	6.6 (IQR 4 to 10)
Length of follow up, years, median (IQR)	9 (IQR 5 to 12)	8 (IQR 5 to 11)
Highest ever CK, u/l, median (IQR)	220 (IQR 111 to 1132)	129 (88 to 157)

^aNine patients were classified as having focal myositis or other idiopathic inflammatory myopathy; ^bOne Black-African patient, one Indian patient, one Pakastani patient and two patients from other ethnic groups. All anti-MDA5 autoantibody-positive patients had juvenile dermatomyositis (JDM). Otherwise, demographic data did not differ significantly between anti-MDA5 antibody positive patients and the overall cohort. IQR, interquartile range; CK, creatine kinase.

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