Track: Clinical Studies

Topic: Inflammatory Diseases

Abstract:

Background: Maculopapular cutaneous mastocytosis (MPCM) is a rare disorder characterized by a pathologic accumulation of mast cells in the skin with or without systemic mastocytosis. Diagnosis of MPCM on skin biopsy can be challenging as there are overlapping features with urticaria, normal skin, and other inflammatory dermatoses. Identifying differentiating features including mast cell density would be helpful in the diagnosis of MPCM.

Methods: We identified adult patients diagnosed with MPCM and urticarial tissue reaction/chronic urticaria on skin biopsy and compared the mast cell and eosinophil counts in 10 cases of each MPCM, chronic urticaria and normal skin from routine biopsies. All slides were stained with CD117, and CD117+ mast cells were counted per 1 mm2 using digital microscopy.

Results: The mean mast cell density was significantly higher in mastocytosis cases than in chronic urticaria and case controls (209 vs 32 vs 53 mast cells/mm^2, p= <0.001). The median number of mast cells per 1 mm2 in mastocytosis was 188.0 (158.500, 272.250) and in chronic urticaria was 28.5 (24.250, 38.750). The cut point for mastocytosis versus chronic urticaria was 76 mast cells whereas the cut value for mastocytosis versus controls was 42. There was no significant difference in eosinophil count between mastocytosis and chronic urticaria (11 vs 14 eosinophils/ mm^2, p= 0.6).

Conclusion: This study adds to the literature to provide numerical data for distinguishing challenging cases of cutaneous mastocytosis from urticarial reactions. Future studies could explore the development of computer-aided estimations of cellular density to translate our findings into clinical practice.

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Annie King, MD