Background/Purpose:  With the advent of new therapies, outcomes for children with juvenile dermatomyositis (JDM) have significantly improved. Accurate markers of clinically inactivedisease are thus fundamental in the effort to reduce unnecessary prolongation of treatment. Muscle enzymes are frequently monitored, however individual enzyme levels do not always correlate with disease activity. Von Willebrand factor (vWF) antigen has been shown to be elevated in children with active JDM, albeit without specificity and absolute consistency. This study aims to evaluate the utility of normal vWF antigen as an indicator of disease quiescence, as well as the usefulness of vWF antigen levels in the assessment of disease flare.

Methods:  This longitudinal, retrospective cohort study analyzed disease activity of children with JDM from January 2009 to April 2014, evaluating serial clinical and laboratory measurements. Disease flare was defined by the presence of 2 or more of the following: elevation in muscle enzymes, worsening muscle strength (manual muscle testing – MMT) or functional ability (Childhood Myositis Assessment Scale – CMAS), worsening extramuscular manifestations or worsening physician global assessment of disease activity (PhyGloVAS). Disease inactivity was defined according to modified PRINTO criteria: 3 of the 4 following elements: creatine kinase≤150, CMAS score≥48, MMT≥78 and PhyGloVAS≤0.2.

Results: A total of 357 visits were evaluated from 22 patients. The median number of visits per patient was 12 (IQR: 7-17). Using modified PRINTO criteria, 77/357 (22%) visits met criteria for disease inactivity. In multivariate analysis, the odds of children with normal vWF antigen levels to be in a state of disease quiescence was 3 times greater than the odds of those with abnormal levels after controlling for age, gender and disease duration (p<0.0001) (Table 1).
Laboratory values taken from a previous visit (within 3 months duration of a flare) were assessed in separate multivariate analyses as predictors of the upcoming flare (Table 2).

Conclusion: With improved therapies, clinical remission in JDM is an
achievable goal. Accurately identifying children with inactive disease is critical in reducing long-term treatment toxicity and overall morbidity. This data supports the use of vWF antigen, LDH and AST as predictors of disease flare; while traditional markers, CPK and aldolase, were less reliable markers of flare. To our knowledge, this is the first study to demonstrate the utility of normalization of vWF antigen in defining clinically inactive disease.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-role-of-von-willebrand-factor-antigen-as-a-disease-biomarker-in-the-clinical-assessment-of-children-with-juvenile-dermatomyositis/