Mast cell activation syndrome (MCAS) is a term referring to one of two types of mast cell activation disorder (MCAD); the other type is idiopathic MCAD. MCAS is an immunological condition in which mast cells inappropriately and excessively release chemical mediators, resulting in a range of chronic symptoms, sometimes including anaphylaxis or near-anaphylaxis attacks. Primary symptoms include cardiovascular, dermatological, gastrointestinal, neurological and respiratory problems.
MCAS is an umbrella term that describes a set of symptoms; it is not a specific diagnosis. Multiple diagnostic schemes for MCAS have been proposed. MCAS has been increasingly over-diagnosed or misdiagnosed.
MCAS is an inflammatory condition that affects multiple systems. MCAS can present with a wide range of symptoms in multiple body systems, these symptoms may range from digestive discomfort to chronic pain, mental issues as well as an anaphylactic reaction. Symptoms typically wax and wane over time, varying in severity and duration. Many signs and symptoms are the same as those for mastocytosis, because both conditions result in too many mediators released by mast cells. It has many overlapping characteristics with recurrent idiopathic anaphylaxis, although there are distinguishing symptoms, specifically hives and angioedema. The condition may be mild until exacerbated by stressful life events, or symptoms may develop and slowly trend worse with time. MCAS symptoms are common in long COVID.
Common symptoms include:
Dermatological
flushing
hives
easy bruising
either a reddish or a pale complexion
itchiness
burning feeling
dermatographism
Cardiovascular
lightheadedness, dizziness, non-cardiac chestpain, presyncope, syncope, arrhythmia, tachycardia
Gastrointestinal
diarrhea and/or constipation, cramping, intestinal discomfort
nausea, vomiting, acid reflux
swallowing difficulty, throat tightness
Neuropsychiatric
brain fog
headache
fatigue/lethargy
lack of concentration
mild cognitive problems
sleep disturbances
Respiratory
congestion, coughing, wheezing
Systemic
Anaphylaxis
There are many causes of mast cell activation, including allergy.