Venn diagram showing overlap between iMCD and other entities with similar clinical and pathologic presentations which must be excluded before making the diagnosis ALPS, autoimmune lymphoproliferative syndrome; AOSD, adult-onset Still disease; EBV, Epstein-Barr virus; FDC, follicular dendritic cell; HL, Hodgkin lymphoma; HLH-MAS, hemophagocytic lymphohistiocytosis- macrophage activation syndrome; IgG4, IgG4-related disease; JIA, juvenile idiopathic arthritis; M-HLH, malignancy-associated hemophagocytic lymphohistiocytosis; NHL, non-Hodgkin lymphoma; POEMS, polyneuropathy, organomegaly, endocrinopathy, monoclonal paraprotein, skin changes; RA, rheumatoid arthritis; SLE, systemic lupus erythematosus; V-HLH, viral hemophagocytic lymphohistiocytosis. See Figure 1 in the article by Fajgenbaum et al that begins on page 1646.