Juvenile systemic arthritis

**Definition:** Systemic-onset juvenile idiopathic arthritis represents 10-11% of cases of juvenile idiopathic arthritis (JIA) and is marked by the severity of the extra-articular manifestations (fever, cutaneous eruptions) and by an equal sex ratio. Fever peaks are associated with transient cutaneous eruptions and diffuse erythematosis or urticarial-like lesions. The presence of arthritis is essential for diagnosis but may appear later in the disease course. The number of sites affected is variable (mono-, oligo- or polyarthritis) affecting both the small and large joints in a nearly symmetrical manner. This characteristic diagnostic triad may also be associated with an adenopathy and hepatosplenomegaly. Visceral complications (pericarditis, pleural effusion or serous peritonitis with abdominal pain) may be present.