Figure 4.

Criteria for diagnosis of mast cell activating syndrome (please refer to text for description). A = clinical criterion, B = laboratory criterion, C = treatment criterion. All three criteria need to be satisfied to confirm a diagnosis of mast cell activation syndrome (MCAS). The presence of clonality (KIT D816V mutation or surface expression of CD2 or CD25 clonal markers) would suggest a diagnosis of clonal (primary) mast cell activating syndrome also referred to as the monoclonal mast cell activation syndrome (MMAS). * Tryptase (total tryptase) is usually used as a surrogate marker for mast cell activation. PG = prostaglandin, LT-leukotriene, MCA = mast cell activation. bST = basal serum tryptase.