Kawasaki syndrome, also known as mucocutaneous lymph node syndrome, is a form of acute vasculitis that occurs almost exclusively in young children. In fact, approximately 80% of cases occur in children under 5 years old. This syndrome is extremely rare in children older than age 10. Etiology of the illness is unknown, but many experts agree that an infection (viral or bacterial) is likely, although a genetic predisposition may also play a role.