Epidemiology of rheumatic disease in children.

Major problems associated with interpreting and comparing epidemiologic studies on chronic arthropathies in children include the diversity of classification criteria and selection bias. A new set of classification criteria for peripheral arthritis in children, aiming toward defining biologically homogeneous subgroups, was recently proposed and should be further tested. Descriptive studies from all over the world are now emerging on childhood rheumatic diseases, increasing the potential for comparing the impact of genetic and environmental factors on disease frequency and manifestations. Awareness about pain syndromes in children, such as juvenile primary fibromyalgia and reflex sympathetic dystrophy, has increased, and this population now forms a substantial portion of clinic visits in pediatric rheumatology. The impact of the rheumatic diseases in children on disability and quality of life during childhood and in adult life is still to a large extent unknown and must be further studied in an epidemiologic context.