Background/Purpose:  Determinants of changes in disease activity among patients with juvenile dermatomyositis (JDM) are unknown. Our objective was to develop scores to predict changes in disease activity over the next 6 months among children with active disease at baseline using the CARRA registry.

Methods:   The CARRA registry included 658 subjects enrolled between May 2010 and October 2014 with definite or probably JDM defined based on Bohan and Peter criteria, which were modified to include magnetic resonance imaging. Among the 297 subjects with at least one follow-up visit between 4 and 10 months (median 6 months) after baseline, we studied the 65 subjects with active disease at baseline(defined as physician global ≥3 of 10). Linear regression models were used to build risk scores for changes in disease activity adjusted for baseline disease activity, age, sex and disease duration.

Results:   The study population included 65 patients (mean age at baseline: 9.3 (SD 4.4) years; 66% female; 72% white) with median disease duration of 1.7 (range: 0.1 to 15.2) years. Disease activity improved significantly from baseline to 6 month follow-up as measured by patient global health score (median 4; IQR 2-6 at baseline vs median 2; IQR 1-5 at follow-up; p=0.008), patient pain score (median 2; IQR 0-5.5 to median 1.0, IQR 0=4; p=0.014), physician global (median: 4, IQR: 3-6 to 2, IQR 1-3; p<0.001) and Childhood Myositis Assessment Scale (CMAS) (median 41, IQR 33-47 to median 47, IQR 43-51; p<0.001). Anti-nuclear antibodies (p=0.013) and hydroxychloroquine use (p=0.045) were significant predictors of less improvement in patient global after adjusting for age, sex, disease duration and baseline patient global (R-square improved from 0.19 for adjustors alone to 0.34 for the full model). Anti-nuclear antibodies (p=0.001) and V/shawl sign (p=0.005) were significant predictors of less improvement in patient pain after adjusting for age, sex, disease duration and baseline patient pain (R-square improved from 0.29 for adjustors alone to 0.46 for the full model). There were no identified risk factors for improvement in physician global after adjustment for physician global at baseline, age, sex and disease duration. Small joint arthritis (p<0.01) predicted less improvement and dysphagia/dysphonia (p=0.033) predicted greater improvement in CMAS after adjusting for age, sex, disease duration and baseline CMAS (R-square improved from 0.73 for adjustors alone to 0.86 for the full model).

Conclusion:   Disease characteristics can help identify patients who are less likely to improve over time. Risk scores to predict future changes in disease activity could be used to trigger more aggressive treatment earlier in the disease course.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/predictors-of-changes-in-disease-activity-among-children-with-juvenile-dermatomyositis/