In patients with juvenile dermatomyositis (JDM), the integration of clinical features with laboratory and biopsy findings may help in predicting disease course and guiding treatment decisions, according to study results published in Seminars in Arthritis and Rheumatism.

Researchers aimed to report on the clinical characteristics, muscle biopsy scores, and myositis-specific antibodies (MSAs) related to disease outcomes, treatment responses, and functional outcomes in patients with JDM.

The retrospective cohort study included patients with JDM from a tertiary care center — Hacettepe University, Department of Pediatrics, Divisions of Rheumatology and Neurology — in Ankara, Turkey. Study inclusion criteria were patients aged 18 years or less with confirmed or suspected JDM, according to the Bohan and Peter criteria.


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A total of 58 patients (35 girls) with JDM who had been followed up with (mean follow-up period, 5.66±3.59 years) at a single tertiary care center between 2000 and 2020 were included in the current analysis. Mean participant age at disease onset and time of diagnosis was 8.1 years and 8.7 years, respectively.

Researchers noted that dermatologic manifestations and symmetrical proximal muscle weakness were the key diagnostic elements (91% and 76%, respectively). They observed elevated serum creatine kinase levels in 86% of the study participants, electromyography indicative of myopathy in 92%, magnetic resonance imaging (MRI) showing myositis in 80%, and muscle biopsy with features of JDM in 100%.

Of 46 patients who were evaluated for MSAs and myositis-associated antibodies, 34 tested positive. Elevated creatine kinase and lactate dehydrogenase levels were found to be the 2 most prominent laboratory features. Muscle involvement and elevated serum creatine kinase levels were more frequent among patients with NXP2, TIF1g, and Mi-2 antibodies and less common among those who tested MDA5-positive. In fact, the presence of TIF1g and NXP2 were indicative of severe disease course, and the presence of Ku was suggestive of a very resistant form of the disease with persistently high muscle enzymes and disability.

All patients initially received treatment with 10 to 20 mg/kg/day of corticosteroids, with 93% of patients also receiving 12.5 to 15 mg/m2/week of methotrexate combination therapy. A total of 22% of the patient cohort also received biologic disease-modifying antirheumatic drugs. The most frequently encountered long-term complication was calcinosis, which was reported in 36% of study participants. Calcinosis was associated with disease onset at age 6 years or less, MDA5 positivity, and higher muscle biopsy scores. Overall, 65.5% of patients attained complete remission in a median of 24 months, with a relapse rate of 26.3%.

One of the limitations of the analysis included the possible change in diagnostic tools and parameters during the study period due to its retrospective design.

Researchers concluded, “Combining clinical phenotype with paraclinical examinations will hopefully increase the yield for diagnosis, course, and prognosis, and [individualized] patient-management.”

Reference

Sag E, Demir S, Bilginer Y, et al. Clinical features, muscle biopsy scores, myositis specific antibody profiles and outcome in juvenile dermatomyositis. Semin Arthritis Rheum. 2020;51(1):95-100. doi:10.1016/j.semarthrit.2020.10.007