Laboratorial analysis of patients with active sJIA may reveal granulocytosis, thrombocytosis, anaemia, upregulation of acute phase reactants (elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), which are typical findings but not so essential for diagnosis in comparison with the life-threatening complication of MAS that include pancytopaenia, increased levels of ferritin, liver enzymes (aspartate and alanine transaminases), triglycerides, d-Dimers and hypofibrinogenemia [7]. This evidence concerns the gene CRP and macrophage activation syndrome.