Mast cell activation syndrome (MCAS) is a chronic multisystem illness of general themes of inflammation ± allergic-type phenomena ± abnormalities in growth/development in potentially any tissue. Mast cells produce and release, under a variety of circumstances, a very large number of potent molecular signals generically called mediators, and each mast cell mediator can bring about a wide variety of effects in a very wide variety of tissues, organs, and systems throughout the body, leading to a situation where inappropriate mast cell mediator production/release can result in an array of clinical problems, and yet the problems suffered by one MCAS patient can be extremely different from the problems suffered by another MCAS patient. The problems suffered by an MCAS patient at one point in time can even be different from the problems suffered by the same patient at other points in time. Below are some of the more common symptoms which can be experienced by MCAS patients. It is important to keep in mind that each MCAS patient has a unique experience altogether with the disease.

Common constitutional symptoms of Mast Cell Activation Syndrome (MCAS) include fatigue, malaise, suddenly feeling hot or cold, inappropriate sweats, flushing, unprovoked changes in appetite or weight.

Dermatologic: Common dermatologic symptoms of MCAS include rashes and lesions of many sorts (e.g., migratory and waxing/waning patches of redness, acne-like folliculitis), itching, flushing (sometimes migratory), swelling (often migratory), pregnancy-like purplish lines/bands (“striae”) about the abdomen, flanks, armpits and/or hips, redness in the track of a scratch (“dermatographism”), poor healing, and nail issues (e.g., brittleness, longitudinal ridging, “white spots” (dyshydrotic eczema); ingrown nails, too, are seen sometimes).

Ophthalmologic: Common eye symptoms include irritation and inflammation of the eyes (often described as feeling “sandy,” “gritty,” “dry,” and usually without any clear infection to account for it), usually fairly brief episodes of difficulty focusing vision, eyelid tremors/tics (“blepharospasm”), and unusual sensitivity to either bright lights or lights of certain colors.

Otologic: Common ear symptoms include ringing in the ears and irritation and inflammation in the ears. Less common are a sense of chronic fluid build-up in the ears, hearing loss (one-sided or two-sided), or uncomfortable heightened hearing sensitivity.

Nasal/Oral: Common oral and nasal symptoms include ulcers and pain (sometimes described as “burning”), white patches about the tongue or other surfaces, swelling of the tongue or other surfaces, sensitivity and/or deterioration of the teeth and/or gums despite reasonably good attention to dental and gum hygiene, alterations in the sense of taste, throat irritation/soreness/inflammation and/or hoarseness (without any infection clearly being present to account for it), difficulty swallowing, congestion of the sinuses and nose, sores up inside the nose, and nasal and post-nasal drip.

Lymphatic: Common symptoms of the lymphatic system include a diffusely migratory, waxing/waning enlargement and/or irritation/inflammation of the lymph nodes, typically about the neck and in either armpit and to either side of the groin, but possibly in other areas, too (including in the spleen, the body’s largest lymph node, which often is felt as a left upper quadrant abdominal discomfort).

Respiratory: Common respiratory tract symptoms include painful discomfort at any level of the respiratory tract, bronchitis, cough, shortness of breath (often modest and inconstant; “from time to time, I just suddenly can’t catch a deep breath” is the most common phrasing MCAS patients use to describe their shortness of breath). Frank wheezing is not seen all that often, and when it’s present during the episodes of shortness of breath, it’s usually fairly subtle. Obstructive sleep apnea can happen, too, even in patients who are not morbidly obese.

Cardiovascular: Common cardiovascular symptoms and findings include palpitations, lightheadedness, unexplained/unexpected hypertension and/or hypotension, palpitations, chest discomfort or pain (usually non-anginal in character), vascular malformations such as aneurysms or hemorrhoids or hemangiomas or telangiectasias).

Gastrointestinal: Common gastrointestinal symptoms include pain/inflammation (often migratory) in one or more segments of the GI tract, gastroesophageal reflux, abdominal discomfort/pain, abdominal bloating (usually shortly following meals), unexplained/unexpected fluctuations in appetite and/or weight, queasiness, nausea (vomiting is relatively uncommon), and diarrhea (or “soft stools”) and/or constipation (often alternating). Blood in the stool can happen but is pretty uncommon.

Urinary: Common urinary symptoms include unusual frequency of urination, difficulty initiating urination, inability to fully empty the bladder, and painful urination (as if a urinary tract infection is present, except that testing can’t find clear evidence of infection). Flank or abdominal pain from kidney stones can happen but is not all that common. Blood in the urine can happen but is pretty uncommon.

Genital Tract: Other than decreased libido and erectile dysfunction and possible fertility issues, genital tract symptoms are uncommon in men but may include inflammation of the prostate or other parts of the genital tract. In women with MCAS, genital tract symptoms are common and include an inflamed and/or itchy vulva and/or vagina (often mistakenly attributed to, and treated as, bacterial or yeast infections even though no evidence of infection can be found), inappropriate/dysfunctional uterine/menstrual bleeding, and painful intercourse. Endometriosis seems somewhat common, too.

Pregnancy: Women who have MCAS also can have decreased libido and fertility challenges. Women with MCAS who become pregnant sometimes experience early miscarriages, excessively severe or prolonged vomiting (“hyperemesis gravidarum”), the assortment of high blood pressure and other problems collectively called pre-eclampsia, and pre-term labor. In delivery, women with MCAS sometimes find difficulties tolerating, or getting relief from, anesthetics.

Muscular: Common muscular symptoms include migratory pain and weakness.

Skeletal: Common skeletal symptoms include migratory pain. Fractures are uncommon but can happen from loss of skeletal strength, and these include vertebral fractures which can lead to loss of height.

Joint: Common joint symptoms include migratory pain; migratory swelling and even redness, too, can happen, but usually are not as prominent as pain.

Neurologic: Common neurologic symptoms include headache (including migraines), episodic lightheadedness/dizziness/vertigo (which can happen either when getting up or even when lying down or sitting or after already been up for a while) (total loss of consciousness can happen but is much less common than lightheadedness), tingling/numbness (most commonly in the hands and feet but potentially anywhere), weakness, tics/tremors, and a wide variety of sleep disruptions (most commonly insomnia and frequent waking and non-restorative sleep but also excessive sleep, sleepwalking or sleep talking, sleep paralysis, or night terrors).

Psychiatric: Common psychiatric symptoms include anxiety (sometimes even to the point of panic), depression, mood lability, anger, attention deficit, and a wide variety of aspects of cognitive dysfunction, most commonly issues with memory, word-finding and concentration. “Disassociation” or “depersonalization” is occasionally seen. Frankly psychotic behaviors (e.g., auditory or visual hallucinations) are fairly uncommon.

Endocrinology: Common endocrinologic/metabolic issues include delayed or premature puberty, excessively painful and/or irregular periods, excessive menstrual bleeding, weak bones, thyroid abnormalities, high cholesterol or triglycerides, high glucose levels (usually diagnosed as diabetes mellitus) or low glucose levels (sometimes rapid alternation among normal and low and/or high levels), and selective abnormalities in absorbing or transporting or using certain important minerals and vitamins (e.g., iron).

Hematologic: Common hematologic and clotting system issues include modest abnormalities in blood counts, easy bruising, and easy bleeding (for example, excessive menstrual bleeding or easy nosebleeds). Excessive blood clotting is a good bit less common than easy bruising/bleeding.

Immunologic: Common immunologic issues include prolific and/or unusual sensitivities/reactivities/allergies, impaired healing, an unusual extent of autoimmune diseases, increased susceptibility to infection, and difficulty recovering from infection.

Mast Cell Activation Syndrome causes chronic multisystem inflammation ± allergic-type phenomena ± abnormalities in growth/development in potentially any tissue(s), so any patient who “fits the profile” and hasn’t been identified, with appropriate work-up of the various individual problems, to have any other disease which better accounts for the patient’s full range of problems is a reasonable candidate to be evaluated for MCAS.

Additional MCAS article links:

Often seen, rarely recognized: mast cell activation disease – a guide to diagnosis and therapeutic options

Characterization of Mast Cell Activation Syndrome