Progression of Mast Cell Activation Syndrome to Systemic Mastocytosis

Abstract Introduction/Objective Mast cell activation syndrome (MCAS) is characterized by the abnormal release of mast cell mediators, leading to symptoms such as flushing, abdominal pain, and allergic reactions. In some cases, MCAS progresses to systemic mastocytosis (SM), a mast cell disorder marked by organ infiltration and dysfunction. However, predictors of MCAS progression to SM remain poorly understood, and long-term prognosis data are limited. Methods/Case Report We conducted a retrospective study of patients diagnosed with MCAS at Penn Medicine from January 1, 2019, through December 30, 2021. The primary endpoint was progression to SM, defined by World Health Organization criteria, with a secondary endpoint set for September 24, 2023. Results (if a Case Study enter NA) We identified 47 patients with MCAS (Table 1). Of these, 11 patients (23.4%) progressed to SM. Notably, all five patients with c-KIT mutations progressed to SM (100%, 5/5), while six out of 22 patients without c-KIT mutations also progressed (27.2%). Additionally, baseline serum tryptase levels were identified as a significant predictor of progression at two years. Conclusion The relative risk of progression varied depending on the subtype of MCAS, with higher rates observed in those with KIT D816V presence. Compared to the incidence of SM in the general population, our findings suggest a higher risk of progression from MCAS to SM, even without a c-KIT mutation. Identification of prognostic factors, such as specific genetic mutations and baseline serum tryptase levels, may aid in risk stratification and early intervention strategies for individuals with MCAS. HaT mutation testing should be considered in future studies on this topic. Our findings have important implications for the clinical management and understanding of MCAS progression to SM. Additionally, our data imply the importance of recognizing MCAS in the early phase and proper monitoring, considering the low rate of MCAS diagnosis. Patients with MCAS may need annual monitoring, including serum tryptase levels, to detect progression to SM and related complications. Early detection and intervention may improve outcomes and quality of life for individuals with MCAS.