Whole-Exome Sequencing Reveals Overlap Between Macrophage Activation Syndrome in Systemic Juvenile Idiopathic Arthritis and Familial Hemophagocytic Lymphohistiocytosis

Objective Macrophage activation syndrome (MAS), a life-threatening complication of systemic Juvenile Idiopathic Arthritis (SJIA), resembles Familial Hemophagocytic Lymphohistiocytosis (FHLH), a constellation of autosomal recessive immune disorders resulting from deficiency in cytolytic pathway proteins. We hypothesized that MAS predisposition in SJIA could be attributed to rare gene sequence variants affecting the cytotolytic pathway.