(HealthDay News) – Short-term ultraviolet radiation (UVR) exposure may contribute to the development of juvenile myositis, according to a study published in the July issue of Arthritis & Rheumatism.

Mona Shah, PhD, from the National Institutes of Health in Bethesda, MD, and colleagues examined the correlation between UVR exposure in the month prior to symptom onset and the prevalence of juvenile dermatomyositis (JDM) vs. polymyositis (JPM) in 298 patients. The correlation between UVR exposure and myositis autoantibodies was evaluated among patients with JDM.

The researchers found that, in girls, the odds of JDM vs. JPM increased per unit increase in the patients’ highest UV index in the month before symptom onset (odds ratio [OR], 1.18; 95% confidence interval, 1–1.4). Increasing odds of anti-p155/140 autoantibodies were seen in correlation with average and highest UV indices, a finding that was strongest in white males (OR, 1.3 and 1.23, respectively). There was no correlation seen between the UV index and anti-MJ autoantibodies or patients without myositis autoantibodies. The average UV index was associated with increasing odds of JDM and anti-p155/140 autoantibodies and with decreasing odds of anti-MJ autoantibodies across U.S. geoclimatic regions.

“This study adds important information about the impact of UVR on autoimmune muscle disease,” write the authors. “The association of UVR with JDM and with anti-p155/140 autoantibodies has implications for photoprotective prevention measures, as well as for research regarding the role of UVR in the pathogenesis of myositis in children.”

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