Background There is limited knowledge about persistent disease activity and frequency of inactive disease in Juvenile Dermatomyositis (JDM) patients after long-term follow-up.
Objectives To apply the Myositis Disease Activity Assessment Tool (MDAAT) and Pediatric Rheumatology International Trials Organization (PRINTO) criteria for inactive disease in JDM patients after long-term follow-up, and to examine associations between clinically inactive disease, MDAAT, and other validated disease activity measures.
Methods Inclusion criteria were probable or definitive Dermatomyositis (Bohan/Peter criteria), disease onset before 18 years and minimum 2 years disease duration. A retrospective inception cohort of 60 JDM patients (60% female) was clinically examined median 16.8 years (range 2–38 years) after disease onset. The cohort was divided in patients with inactive (JDM-inactive) and active disease (JDM-active) by the PRINTO criteria; at least three of four of: CK≤150, Child Myositis Assessment Scale (CMAS) ≥ 48, Manual Muscle Test (MMT) ≥ 78 and physician global disease activity (PhyGloVAS) ≤ 0.2. Disease activity was also measured by MDAAT (Myositis Intention-to-Treat Activity Index (MITAX) and the Myositis Disease Activity Assessment Visual Analog Scales (MYOACT)), Disease Activity Score (DAS), patient/parent overall disease activity (PtsGloVAS) and child-HAQ/HAQ.
Results Thirty patients (50%) had inactive disease (15 female); disease duration in JDM-active and JDM-inactive were comparable. All variables included in the PRINTO composite score for inactive disease clearly differed between the two groups (P`s < 0.001), except for CK which was similar (P=0.660). At follow-up, 18/60 (30%) used at least one anti-inflammatory drug; 14 of these were JDM-active. Of JDM-inactive patients, 4/30 patients were inactive on medication and 26/30 inactive off medication. By MYOACT, disease activity was most common in the skin (58%), skeletal (28%) and constitutional and muscle domains (both 18%). MYOACT global and MYOACT extramuscular both showed a strong correlation with DAS and PhyGloVAS (rs`s ≥ 0.85) and a moderate correlation with PtsGloVAS, CMAS, MMT, and CHAQ/HAQ (rs`s 0.32-0.49).
Conclusions Median 16.8 years after disease onset, 50% of JDM patients had clinically inactive disease which was highly associated with low disease activity measured by MDAAT and DAS.
Disclosure of Interest None Declared
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