Systemic onset disease occurs throughout childhood. Diagnosis of systemic arthritis requires the presence of arthritis accompanied or preceded by at least 2 weeks of quotidian fever plus typical evanescent rash (discrete, circumcised, salmon-colored, 2- to 10-mm macules on the trunk and proximal extremities that typically coincide with fever), hepatomegaly, splenomegaly, generalized lymphadenopathy, or serositis. The onset of joint disease may be significantly delayed, which can obscure the diagnosis of JIA. Patients may be ill-appearing and have myalgias and abdominal pain during episodes of fever. Laboratory findings include leukocytosis with a preponderance of neutrophils, elevated liver enzymes, microcytic anemia, thrombocytosis, and very high ESR and CRP concentrations. The ANA titer is rarely positive.19 In approximately 50% of cases, systemic-onset JIA is associated with a relapsing-remitting course in which arthritis accompanies episodes of fever and remits when systemic features are controlled. In the other 50% of patients, it is associated with an unremitting, debilitating arthritis with few systemic symptoms. Other complications include the development of pericarditis, which in some cases can result in a clinically significant pericardial effusion, myocarditis, or pleuritis. Very infrequently, patients develop amyloidosis.