122 Telangiectasia Macularis Eruptiva Perstans: A Rare Cutaneous Mastocytosis Subtype with Heterogeneous Systemic Associations in a Single-Center Cohort

Introduction/Objective Cutaneous mastocytosis (CM) contains a spectrum of rare disorders characterized by cutaneous mast cell accumulation. A subset of CM progresses to systemic mastocytosis (SM) involving extracutaneous organs. Telangiectasia macularis eruptiva perstans (TMEP) represents an exceptionally rare subtype of CM. The true frequency with which TMEP coexists with or evolves into SM remains poorly defined, with inconsistent findings across published literature. Methods/Case Report To investigate the institutional incidence of TMEP and assess its clinical trajectory, we conducted a comprehensive retrospective search of dermatopathology and hematopathology records from 2010 to 2024 at a tertiary care academic center. Only three patients fulfilled diagnostic criteria for TMEP during this 15-year interval, underscoring its extraordinary rarity. We reviewed clinical features, histologic findings, serum tryptase levels, and available molecular and bone marrow data for each case. Results Among the three identified cases, only one met the criteria for systemic mastocytosis. This 24-year-old female (Case 1) exhibited typical cutaneous lesions, elevated serum tryptase, low-level KIT D816V positivity, and bone marrow involvement consistent with indolent SM. The second case, a 28-year-old female, demonstrated cutaneous-limited TMEP with borderline serum tryptase and no detectable KIT mutations, suggesting a non-systemic presentation. The third patient, a 68-year-old male undergoing chemotherapy for acute lymphoblastic leukemia, developed lesions mimicking TMEP but showed normal tryptase levels and negative molecular findings, raising the possibility of a chemotherapy-related phenocopy rather than true mast cell disease. Conclusion Our findings highlight the extreme infrequency of TMEP even in a large academic cohort. Only one-third of cases exhibited progression to SM. Heterogeneity in systemic involvement of these cases points to diagnostic ambiguity and emphasizes the need for meticulous integration of clinical, histopathologic, biochemical, and molecular data when evaluating suspected TMEP. Multicenter studies are warranted to explore the clinical trajectory and systemic associations of this elusive entity.