Rare Rheumatology News

Disease Profile

Mast cell activation syndrome

Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.


US Estimated

Europe Estimated

Age of onset





Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)



Mast cell activation syndrome (MCAS) causes a person to have repeated severe allergy symptoms affecting several body systems. In MCAS, mast cells mistakenly release too many chemical agents, resulting in symptoms in the skin, gastrointestinal tract, heart, respiratory, and neurologic systems. Mast cells are present throughout most of our bodies and secrete different chemicals during allergic reactions. Symptoms include episodes of abdominal pain, cramping, diarrhea, flushing, itching, wheezing, coughing, lightheadedness and rapid pulse and low blood pressure. Symptoms can start at any age, but usually begin in adulthood. The cause of MCAS is unknown. Diagnosis is based on the symptoms, clinical exam, and specific laboratory testing. Other conditions may need to be excluded before MCAS can be diagnosed. Treatment includes several combinations of medications used for allergic reactions, such as antihistamines and mast cell stabilizers.[1][2][3][4][5]


Mast cell activation syndrome (MCAS) is diagnosed based on the symptoms, clinical exam, and specific laboratory tests. Other conditions may need to be excluded before MCAS can be diagnosed. Diagnostic criteria for MCAS have been published in the medical literature.[3][4]


Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

Organizations Supporting this Disease

    Learn more

    These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

    Where to Start

      Selected Full-Text Journal Articles


        1. Theoharides TC, Valent P, and Akin C. Mast Cells, Mastocytosis, and Related Disorders. N Engl J Med. July 9, 2015; 373(2):163-172. https://www.ncbi.nlm.nih.gov/pubmed/26154789.
        2. Akin C. Mast cell disorders. UpToDate. Updated: Apr. 03, 2020; https://www.uptodate.com/contents/mast-cell-disorders-an-overview.
        3. Weiler CR, Asten KF, Akin C, Barkoff MS, Bernstein JA, Bonadonna P, et al. AAAAI Mast Cell Disorders Committee Work Group Report: Mast cell activation syndrome (MCAS) diagnosis and management. J Allergy Clin Immunol. Oct 2019; 144(4):883-896. https://pubmed.ncbi.nlm.nih.gov/31476322/.
        4. Frieri M. Mast Cell Activation Syndrome. Clin Rev Allergy Immunol. 2018 Jun;54(3):353-365. Jun 2018; 54(3):353-365. https://pubmed.ncbi.nlm.nih.gov/25944644/.
        5. Afrin LB, Sef S, Menk J, Lazarchick J. Characterization of Mast Cell Activation Syndrome. Am J Med Sci. Mar 2017; 353(3):207-215. https://pubmed.ncbi.nlm.nih.gov/28262205/.

        Rare Rheumatology News