US incidence of juvenile dermatomyositis, 1995-1998: Results from the National Institute of Arthritis and Musculoskeletal and Skin Diseases Registry

Objective. To estimate the incidence of juvenile dermatomyositis (juvenile DM) in the United States between 1995 and 1998. Methods. Physician referrals to the National Institute of Arthritis and Musculoskeletal and Skin Diseases juvenile Dermatomyositis Research Registry and the National Pediatric Rheumatology Disease Registry from Indiana University were utilized for a 2-source capture-recapture estimation of juvenile DM annual incidence. Results. For children 2-17 years of age, the estimated annual incidence rates from 1995 to 1998 in the US ranged from 2.5 to 4.1 juvenile DM cases per million children, and the 4-year average annual rate was 3.2 per million children (95% confidence interval 2.9-3.4). Estimated annual incidence rates by race were 3.4 for white non-Hispanics, 3.3 for African American non-Hispanics, and 2.7 for Hispanics. During the 4-year period of the study, completeness of ascertainment for the combined registries ranged from 56% to 86% and girls were affected more than boys (ratio 2.3:1). Conclusion. This study provides evidence for sex, and possibly racial differences in the risk of juvenile DM in the US.