Juvenile dermatomyositis: clinical characteristics and the relatively high risk of interstitial lung disease

To clarify the clinical features of juvenile dermatomyositis (JDM) in Japanese cases, we retrospectively evaluated the characteristics of 16 children with JDM that were treated at Saitama Children's Medical Center between 1985 and 2004. The age at disease onset ranged from 3.5 to 14.1 years old (7 boys, mean age 7.9 years; 9 girls, mean age 9.2 years). In 14 patients more than two muscle enzymes were elevated at diagnosis. The antinuclear antibody at diagnosis was positive in all girls but one, while it was positive in only two boys (2/7; P<0.01). Three patients were complicated with interstitial lung disease (ILD) (18.8%) and their serum KL-6 levels were already elevated on admission. Our findings suggest that serum KL-6 levels seemed to be sensitive to the detection of ILD in an early phase, and the relatively high frequency of JDM-associated ILD indicated that a careful evaluation of the lungs was therefore required in any individuals with JDM. Of 16 patients, two boys showed a favorable improvement and prognosis without relapse for over 9 years after the termination of treatment. Overall, in girls, there is a tendency to be a delay in the diagnosis/treatment for JDM, and this disease also demonstrated a severe course.