Background Juvenile dermatomyositis (JDM) is a rare condition affecting 2-3 children/million/year. Muscle and skin involvement are key features. The muscle symptoms are frequently the main initial focus: formal measures (Childhood Myositis Assessment Scale - CMAS and Manual Muscle Testing of 8 groups - MMT8) exist to routinely and accurately assess this component of the disease. However the involvement of skin, and its assessment, is a vital aspect. The abbreviated Cutaneous Assessment Tool (CAT) encompassing active skin disease and skin damage, Disease Activity Score (DAS) and Myositis Intention to Treat Activity Index (MITAX), both with skin components, have all been suggested to measure skin disease in JDM; however the optimal tool is unknown.
Objective To compare 3 tools for assessment of skin disease in JDM and correlate them with the physician's 10cm skin visual analogue scale (VAS) in order to define which tool best assesses skin disease in patients with JDM.
Methods Seventy-one patients recruited to the UK JDM Cohort & Biomarker Study were included and assessed for skin disease using the CAT, DAS, MITAX and skin VAS. Markers of muscle disease (CMAS, MMT8, Creatine Kinase (CK) U/L), inflammatory markers (C-reactive protein (CRP) mg/L and Erythocyte sedimentation rate (ESR) mm/hr) and physician's global VAS were recorded. Relationships were evaluated using Spearman's correlations and predictors with linear regression. Inter-rater reliability was assessed using intra-class correlation coefficients.
Results Of the 71 patients assessed 59.2% were female and 71.8% were Caucasian. At the time of assessment the mean (±SD) age was 9.8 (±3.8) years. The mean age at diagnosis was 6.6 (±3.4) years, and mean disease duration at time of assessment was 3.3 (±3.0) years. The skin section of the DAS had the strongest correlation with the skin VAS (DAS skin rs=0.79 p<0.001, MITAX skin rs=0.60 p<0.001 and CAT activity 0.63 p<0.001) – Table 1. DAS skin and CAT Activity scores were both inversely correlated with both CMAS and MMT8 scores, but these correlations were moderate. MITAX skin was also correlated with the MMT8 score, but no significant correlation was noted with the CMAS. There were no significant correlations between CK and any of the tools. No significant correlations were found between the skin tools and the inflammatory markers, CRP and ESR.
Conclusion This study demonstrates that the DAS skin section correlated the best with the skin VAS, used as the gold standard. The DAS skin tool was concise, quick to use and easy to score.
Disclosure of Interest None declared