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About Mast Cell Disorders

Mast cell disorders encompass a spectrum of conditions characterized by abnormal mast cell activation, proliferation, or accumulation in various tissues. These disorders range from systemic mastocytosis with clonal mast cell proliferation to mast cell activation syndrome (MCAS) with normal mast cell numbers but inappropriate activation.

Pathophysiology

Mast cells release inflammatory mediators including histamine, leukotrienes, prostaglandins, and cytokines when activated by IgE-mediated reactions, complement, or direct stimuli. In systemic mastocytosis, mutations in the KIT gene (commonly D816V) lead to uncontrolled mast cell proliferation and accumulation in organs. MCAS involves normal mast cell numbers but excessive degranulation in response to various triggers.

Clinical Reasoning

Diagnosis requires demonstrating elevated mast cell mediators (tryptase, histamine metabolites) during symptomatic episodes, along with clinical improvement with mast cell stabilizers or antihistamines. Systemic mastocytosis is confirmed by bone marrow biopsy showing mast cell aggregates and KIT mutations. Treatment focuses on trigger avoidance, symptomatic management with antihistamines and mast cell stabilizers, and emergency preparedness for severe reactions.

References

  1. Afrin LB, et al. Mast Cell Disorders. StatPearls [Internet]. NCBI Bookshelf. 2024. https://www.ncbi.nlm.nih.gov/books/NBK545148/
  2. Valent P, et al. WHO Classification of Mastocytosis. Blood. 2022;140(11):1200–1214. PMC9479031. https://pmc.ncbi.nlm.nih.gov/articles/PMC9479031/
  3. Arock M, et al. KIT mutation D816V in mastocytosis. J Allergy Clin Immunol. 2015;135(3):585–595. Covers: KIT D816V, serum tryptase, bone marrow criteria, midostaurin. https://www.jacionline.org/article/S0091-6749(14)01752-6/fulltext

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