Background: A 13-year-old girl presented with features typical of systemic juvenile idiopathic arthritis, including fever, rash and arthritis. Her past medical history was unremarkable.
Investigations: Routine investigations, including CBC, serological tests for urea and electrolyte levels, tests of liver function and clotting, measurement of erythrocyte sedimentation rate, cultures of blood, urine and throat swabs, abdominal ultrasonography, echocardiography, bone marrow aspiration, and determination of laboratory parameters, including presence of anti-streptolysin O antibody and levels of C-reactive protein, lactate dehydrogenase, serum ferritin, D-dimer, fibrinogen and ciclosporin. Specialized investigations included measurement of serum levels of interleukin (IL)-1, IL-6, IL-10, tumor necrosis factor and soluble CD25.
Diagnosis: Systemic juvenile idiopathic arthritis complicated by macrophage activation syndrome.
Management: The disease remained active following treatment with intravenous steroid, immunoglobulin and ciclosporin. The patient's disease was successfully controlled following the introduction of anakinra.