Longitudinal Disease Trajectory Of Juvenile Dermatomyositis

Lily Siok Hoon Lim^1,2, Eleanor Pullenayegum³, Dafna D. Gladman⁴, Earl D. Silverman⁵ and Brian M. Feldman⁶, ¹Pediatric Rheumatology, Hospital for Sick Children, Toronto, ON, Canada, ²Institute of Health Policy Management and Evaluation, University of Toronto, Toronto, ON, Canada, ³Child Health Evaluative Sciences, The Hospital for Sick Children, Toronto, ON, Canada, ⁴Division of Rheumatology, University of Toronto, Toronto Western Hospital, Toronto, ON, Canada, ⁵Rheumatology, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada, ⁶Rheumatology, Hospital for Sick Children, Toronto, ON, Canada

Meeting: 2013 ACR/ARHP Annual Meeting

Keywords: dermatomyositis, Epidemiologic methods, longitudinal studies, pediatric rheumatology and statistical methods

Session Information

Title: Pediatric Rheumatology - Clinical and Therapeutic Aspects II: Pediatric Systemic Lupus Erythematosus, Pediatric Vasculitis and Pediatric Myositis

Session Type: Abstract Submissions (ACR)

Background/Purpose:

1) To determine the longitudinal disease activity trajectory of an inception cohort of Juvenile Dermatomyositis (JDM) patients, 2) To identify predictor(s) for longitudinal disease activity trajectory of JDM.

Methods: A single-center, inception cohort of juvenile dermatomyositis (JDM) patients (age of diagnosis <18 years old), recruited within 1 year of their initial presentation was studied. The patients were accrued from January 1991 to December 2010, in a JDM subspecialty clinic. Patients were evaluated at every clinic visit for disease activity with the modified Disease Activity Score (mDAS). Each individual’s mDAS trajectory was plotted and compared to the whole cohort using a trellis plot. Baseline disease features– swallowing difficulty, skin ulcer, calcinosis, duration of symptoms before evaluation, age and gender– were evaluated as predictors of the longitudinal trajectory of JDM. Time-varying treatment status was also tested. Longitudinal trajectory modeling was performed with mixed random effects modeling (random slopes).

Results: Ninety-five JDM patients (33 males, 35%) were studied. The median age of onset was 7.8 (25^th-75^th percentile (P): 4.9- 12.1) years. The median mDAS score at presentation was 7 (25^th-75^th P: 6-9), the median skin subscale score was 3(25^th-75^th P:2-4), the median musculoskeletal subscale was 4 (25^th-75^th P: 3-6). The median duration of follow-up was 4.6 (25^th-75^th P: 2.4- 6.9) years. All patients in the cohort were treated with a standardized protocol comprising prednisone alone (before 2000) or methotrexate (MTX) and prednisone (after 2000). The disease trajectory of mDAS in this inception cohort followed a rapid reduction of activity within the first 2 years with a minor flare in disease activity beyond 2 years. Swallowing difficulty was associated with higher mDAS at diagnosis. Treatment with MTX 3 months before and baseline swallowing difficulty predicted faster improvement in mDAS trajectory.

Conclusion: Disease activity trajectory of JDM showed a general rapid reduction of mDAS followed by a small flare of disease activity beyond 2 years. Although difficulty with swallowing at presentation was associated with higher mDAS at diagnosis, it did not predict a slower rate of response of mDAS to treatment.

Disclosure:

L. S. H. Lim,
None;

E. Pullenayegum,
None;

D. D. Gladman,
None;

E. D. Silverman,
None;

B. M. Feldman,
None.

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