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Mast cell activation syndrome

Last reviewed: 5 Oct 2024
Last updated: 21 Jun 2023

Summary

Definition

History and exam

Key diagnostic factors

  • recurrent episodes of anaphylaxis
  • acute-onset cardiovascular symptoms and signs of mast cell activation
  • acute-onset skin symptoms and signs of mast cell activation
  • acute-onset respiratory/naso-ocular symptoms and signs of mast cell activation
  • acute-onset gastrointestinal symptoms and signs of mast cell activation
  • allergic or other trigger for acute onset of symptoms
  • positive response to mast cell mediator medication
  • skin signs of mastocytosis
Full details

Other diagnostic factors

  • neurological symptoms
  • musculoskeletal symptoms
Full details

Risk factors

  • mastocytosis
  • atopic predisposition
  • history of unprovoked anaphylaxis
  • hereditary alpha-tryptasaemia
Full details

Diagnostic investigations

1st investigations to order

  • serum tryptase
  • urinary metabolites of histamine and/or prostaglandin D2 and/ or leukotriene C4 (LTC4)
  • 12-lead ECG
Full details

Investigations to consider

  • allergy work-up
  • peripheral blood KIT D816V mutation analysis
  • bone marrow biopsy
  • trial of mast cell mediator blocking agent/mast cell stabiliser
Full details

Treatment algorithm

INITIAL

acute MCAS: anaphylaxis episode

ONGOING

confirmed MCAS (all subtypes): long-term management

Contributors

Authors

Cem Akin, MD, PhD

Clinical Professor of Allergy and Immunology

University of Michigan Health

Ann Arbor

MI

Disclosures

CA has consultancy agreements with Blueprint Medicines, Cogent, and Novartis, and receives contract research support from Blueprint Medicines and Cogent. CA is also a member of the board of directors of the American Academy of Allergy, Asthma and Immunology (AAAAI).

Theo Gulen, MD, PhD

Senior Consultant Allergist

Department of Respiratory Medicine and Allergic Diseases

Karolinska University Hospital

Karolinska Institutet and Mastocytosis Cente

Stockholm

Sweden

Disclosures

TG declares that he has no competing interests.

Peer reviewers

Mariana Castells, MD, PhD

Director

Mastocytosis Center and Drug Hypersensitivity and Desensitization Center

Brigham and Women’s Hospital

Professor of Medicine

Harvard Medical School

Boston

MA

Disclosures

MC is the principal investigator for two clinical trials for Blueprint Medicines (using tyrosine kinase inhibitors for indolent systemic mastocytosis); the principal investigator for a Cogent clinical trial for patients with non-advanced clonal mast cell activation disorders. MC is also a consultant for Daiichi Sankyo, the research chair of American Academy of Allergy, Asthma and Immunology Foundation, and director of the American Board of Allergy and Clinical Immunology.

Deepti H Radia, MBBS, MRCPI, FRCPath

Haematology Consultant

Guys and St Thomas’ NHS Foundation Trust

London

UK

Disclosures

DHR has honorary consulting agreements with, and receives educational honoraria/travel support from Blueprint Medicines, Cogent Biosciences and Novartis. DHR is also a member of study steering committees for Blueprint Medicines trials - EXPLORER, PATHFINDER, and Cogent Biosciences trial APEX, and receives research support from Blueprint Medicines.

  • Differentials

    • Somatoform disorders
    • Vasovagal reaction
    • Carcinoid syndrome
    More Differentials
  • Guidelines

    • Updated diagnostic criteria and classification of mast cell disorders: a consensus proposal
    • AAAAI Mast Cell Disorders Committee Work Group Report: mast cell activation syndrome (MCAS) diagnosis and management
    More Guidelines
  • Patient information

    Anaphylaxis

    More Patient information
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