Macrophage activation syndrome as the presenting manifestation of rheumatic diseases in childhood

We describe 3 patients who presented with features of macrophage activation syndrome (MAS) at the time of presentation of systemic lupus erythematosus (SLE), systemic juvenile idiopathic arthritis, and Kawasaki disease. Immunohistochemical studies in the patient with SLE demonstrated extensive expression of CD163 on hemophagocytic macrophages, suggesting a possible role as a marker of MAS.