[Macrophage activation syndrome and Kawasaki disease: Four new cases]

Macrophage activation syndrome (MAS) is a rarely reported complication of Kawasaki disease (KD). It must be sought during KD with unusual clinical signs, such as enlargement of the liver or spleen, cytopenia (including thrombocytopenia), and elevated serum triglycerides. Here, we report four cases from a single center. The first is the description of a case of KD occurring in an 11-month-old child 15 days after the occurrence of infectious spondylitis. For the second, acute myocarditis heralded KD in a 5-year-old child. A 15-year-old boy had multiorgan failure with shock. The last case describes an infant with atypical KD. All had hepatosplenomegaly, thrombocytopenia, and increased serum ferritin. For all of them, hemophagocytosis was present on the bone marrow smears. The condition rapidly evolved favorably with intravenous immunoglobulins or steroids. The extensive microbiological work-up was unrevealing. None had any coronary sequelae after the episode. KD should be added to the list of inflammatory conditions that may be complicated by MAS that modifies the presentation mimicking toxic shock or infection-associated activation syndrome and makes the diagnosis difficult. This association does not appear to have a prognostic impact on the course of the disease in the literature, confirmed by the analysis of this small series.