Peter Vadas MD, PhD Consultant in Allergy and Clinical Immunology
MCAS, Systemic Mastocytosis and COVID-19

Valent P et al.  Risk and management of patients with mastocytosis and MCAS in the SARS-CoV-2 (COVID-19) pandemic: Expert opinions. J Allergy Clin Immunol. 2020 Aug;146(2):300-306. doi: 10.1016/j.jaci.2020.06.009.

Mastocytosis and Hereditary Alpha Tryptasemia
Mast cell disorders are uncommon causes of allergic reactions and anaphylaxis. When mast cells accumulate in the skin, they can cause characteristic skin lesions, such as urticaria pigmentosa or telangiectasia macularis eruptiva perstans (TMEP).  This type of mast cell disorder can be confirmed by skin biopsy.

Sometimes, mast cells accumulate in other areas, such as bone marrow. Diagnosis requires a bone marrow biopsy and specialized molecular studies to test for a mutation in a cell surface regulatory protein.  Treatment includes use of medications that block the actions of mediators released from mast cells (receptor blockers) or drugs that stabilize mast cells to prevent their activation.

One common cause of mast cell activation syndrome is hereditary alpha tryptasemia, where a person may inherit and extra copy of a gene that encodes for an enzyme known as alpha tryptase.  People with lHaT may have mast cell activation syndrome.  Confirmation is by genetic testing in people with a tryptase of 8 mcg/:L or higher.


Vadas P, Guzman J, McGillis L, Mittal N, Walsh S. Consegregation of postural orthostatic tachycardia syndrome, hypermobile Ehlers-Danlos syndrome, and mast cell activation syndrome. 2020 Aug 13. (published online ahead on print, 2020 Aug 13). Ann Allergy Asthma Immunol. 2020:s1081-1206(20)30571-8. doi:10.1016/j.anai.2020.08.015. 

Carrigan C, Milner JD, Lyons JJ, Vadas P. Usefulness of testing for hereditary alpha tryptasemia in symptomatic patients with elevated tryptase. 2020 Jan 12. J Allergy Clin Ummunol Pract. 2020:8(6):2066-2067.doi:10.1016/j.jaip.2020.01012. 

McGillis L, Mittal N, Santa Mina D, et al. Utilization of the 2017 diagnostic criteria for hEDS by the Toronto GoodHope Ehlers-Danlos syndrome clinic: A retrospective review. 2020. Am J Med Genet A. 2020:182(3):484-492.doi:10.1002/ajmg.a61459. 

Slapnicar C, Trinkaus M, Hicks l, Vadas P. Efficacy of Omalizumab in Indolent Systemic Mastocytosis, Case Rep Hematol. 2019:2019:3787586. Published 2019 Sep 16.doi:10.1155/2019/3787586. 2019 Sep 16. 

Slapnicar C, Scullion Smeek C, Hicks L, Petrucci J, Vadas P, Trinkaus M. A retrospective case series describing the efficacy of omalizumab in systemic mastocytosis. 2018. Blood 2018;132:5474

Scullion C, Trinkaus M, Hicks L, Vadas P. Risk factors for anaphylaxis in patients with cutaneous and systemic mastocytosis. 2018. Blood 2018;132:5474. 

Slapnicar C, Scullion C, Hicks L, Petrucci J, Vadas P, Trinkaus M. A retrospective case series describing the efficacy of ketotifen in systemic mastocytosis. 2018. Blood;132:5474. 

Slapnicar C, Scullion C, Hicks L, Trinkaus M, Vadas P. Omalizumab and systemic mastocytosis: a single centre case series. 2018. JACI 2018;12:553.