Correlation Between Interferon Response Gene Score and Disease Activity in Juvenile Dermatomyositis

Type 1 interferons (IFNs) have been identified as potentially important measures of disease activity in juvenile dermatomyositis (JDM). An IFN response gene (IRG) score has been defined using NanoString technology and appears to correlate with disease activity in cross-sectional samples of patients with JDM. This study aimed to determine if there is evidence of a correlation between disease activity and IRG score in patients with JDM, both early in the disease course and longitudinally.

All patients attending the JDM clinic at The Hospital for Sick Children (SickKids), in Toronto, Canada, were approached to enroll in the Childhood Arthritis and Rheumatic Diseases (CARD) biobank. We identified patients with a diagnosis of JDM, enrolled between January 2015 and June 2022. NanoString IRG score was calculated from extracted RNA. The modified Disease Activity Score was calculated based on clinical data collected prospectively through SickKids's JDM registry. Spearman correlation was calculated using all enrollment visit samples, and linear mixed model regression was used for subjects with multiple samples.

Forty-three subjects with 87 biosamples were identified, including 18 treatment-naïve subjects. Spearman correlation at the enrollment visit was strong (r_s 0.78) with similar results seen in the treatment-naïve cohort (r_s 0.63). This relationship persisted over time, with linear mixed modeling of the treatment-naïve cohort showing β coefficient for the IRG score of 0.004 with P < 0.001.

This study shows evidence of a significant correlation between IRG score and disease activity, which is maintained over time. This highlights the potential for IRG score to be an important biomarker in JDM.