Mast cell activation disorders (MCADs)

Mast cell activation (MCA) is common and occurs in a number of conditions, including:

- IgE-dependent and independent allergic reactions
- atopic disorders
- autoimmune processes
- mastocytosis

In a subset of patients with mast cell activation (MCA), no underlying disease and no known trigger are found. This is clearly a challenge for both patients and physicians.

When the symptoms of mast cell activation (MCA) are severe, systemic, and recurrent, and accompanied by a diagnostic increase in the serum tryptase level or other mast cell mediators, an MCA syndrome (MCAS) may be diagnosed.

In patients with MCA syndrome (MCAS), the symptoms typically respond to medications suppressing mast cell activation, mediator production in mast cells, or mediator effects.

Diagnostic consensus criteria must be fulfilled to diagnose MCAS. This is clear. The criteria were listed in prior JACI articles and are also available by using the search function of this website.

In other patients, MCA may be local, less severe, or less acute. They do not have MCAS if the criteria are not fulfilled.

The JACI-IP article linked below discusses MCA disorders (MCADs) and:

- confirmed MCAS
- MCAD not fulfilling MCAS criteria
- suspected MCAD that is not present
- discrimination between overt MCAD and predisposing conditions, such as atopic states, mastocytosis, and hereditary alpha tryptasemia (HaT)

References:

https://www.jaci-inpractice.org/article/S2213-2198(22)00493-7/fulltext