A Puzzling Mast Cell Trilogy: Anaphylaxis, MCAS and Mastocytosis

Our knowledge of biology and mast cell (MC) function, as well as disorders associated with the pathologic activation of MCs has been evolving over the last few decades. Anaphylaxis, mast cell activation syndrome (MCAS) and mastocytosis are interrelated yet distinct conditions within the spectrum of mast cell activation disorders. Nevertheless, all three conditions can co-exist in one and same patient, as pathologic MC activation is the key finding in all three. When mediator release is excessive and involves multiple systems, anaphylaxis and MCAS may occur. Furthermore, mastocytosis is a clonal disorder of MCs and often presents with anaphylaxis and MCAS. Nevertheless, in some cases even proliferative and accumulative features of MCs in mastocytosis can account for symptoms and disease progression. In each case, diagnosis can be only made when diagnostic consensus criteria are fulfilled. The current article aims to provide a concise clinical update and pinpoint main difficulties in diagnosing these puzzling disorders of MCs in medical practice.