Mast Cell Activation Syndrome (MCAS)

Could I have Mast Cell Activation Syndrome?


Every person has had some of these symptoms (listed below) at different times in their lives. That doesn’t necessarily mean you have Mast Cell Activation Syndrome. However, we recommend further investigation if you or a loved one has experienced or is experiencing:


  • Chronic or recurrent episodes of some of these symptoms in multiple systems

  • Workups by healthcare providers of various specialties that didn’t explain or diagnose your symptoms

  • Having several diagnoses but minimal improvements with recommended treatments

  • Adverse reactions to medications and treatments

  • Symptoms and presentations that providers refer to as unusual, odd, idiopathic, unexplained, bizarre, weird, poorly understood, strange.

  • Being told (or having it implied) that your symptoms are all in your head


Mast Cell Activation is a diverse and complex illness that’s only recently been described in medical literature but is quickly becoming recognized for its high degree of prevalence (estimates are as high as 17% of the general population, or 1 in 6). For anyone with a complex medical history, multiple diagnoses or a chronic illness that’s completely unexplained, this percentage is much higher. Our clinical observations among the population we treat are between 2 - 3 times that.


Due to an extremely high number of biological variables, MCAS can present itself in almost limitless ways. It’s primary consequence is widespread systemic inflammation. Overtime, chronic inflammation can cause symptoms, damage and dysfunction in potentially any system of the body. Other common themes in people with MCAS include immune dysregulation, “allergic-type phenomena” and abnormal tissue growth and development.


One of the physicians who played a primary role in discovering MCAS (and is now heavily involved in MCAS research) is hematologist-oncologist Dr. Lawrence Afrin. He titled his book Never Bet Against Occam, based on the principle of “Occam’s Razor,” which is: pluralitas non est ponenda sine necessitate or “plurality should not be posited without necessity.” Paraphrased, his intention is to raise the following question: Rather than one person being so unfortunate as to have a long list of separate health maladies, could there be an underlying pathology that’s capable of causing (directly or indirectly) all of them? Dr. Afrin’s answer is yes. We agree.


It’s important to understand that someone with MCAS may have only a few relatively mild symptoms, while others are affected in every system of the body, and/or with symptoms severe enough to cause a life of absolute misery. It’s also important to know that a person’s symptoms can vary dramatically over time due to an assortment of influences including chronic stress, trauma, mold, toxins, infections (bacterial, viral, fungal), etc.


But, no matter where you or your loved one might be on this spectrum, there's great hope.


Due to lack of awareness and understanding (again, MCAS as a separate and distinct pathology from other mast cell diseases has only recently been identified), the current average length of time between first symptom onset and diagnosis is between 20 - 30 years. We intend to do our part to change that.


With our commitment to education (including patients, the general public, and other providers of various specialties), we hope that fewer and fewer people will have to suffer this way. Given that MCAS can manifest in literally every system, we see a future where providers in every field are educated in recognizing early symptomatology so that interventions can be made far sooner.


We invite you to take a look at this list of possible MCAS symptoms (organized by system) to see if you think MCAS might be a possibility for you or someone you know:

List of Possible MCAS Symptoms


The following list is adapted from: Afrin LB, Molderings GJ. A concise, practical guide to diagnostic assessment for mast cell activation disease. World J Hematol 2014; 3(1): 1-17 [DOI: 10.5315/wjh.v3.i1.1]


Potential manifestations of Mast Cell Activation Disease (most are chronic, low-grade; some are persistent, but many are either episodic or fluctuant).


  • Constitutional: Fatigue, malaise, feeling of weakness, “chronic fatigue syndrome”, subjective and/or objective hyperthermia and/or hypothermia, “sense of feeling cold much of the time”, sweats/diaphoresis (not always nocturnal), flushing, plethora (reddish complexion) or pallor, increased or decreased appetite, early satiety (feeling full when eating), weight gain or loss, itching (without rash), chemical and/or physical environmental sensitivities (often odd) [This can be Multiple Chemical Sensitivity, reactions to fumes, odors, foods, chemicals such as additives to food or fertilizers, etc, reactions to heat, cold, pressure or vibration.]


  • Skin: Rashes and lesions of many sorts (classic urticaria pigmentosa, “freckles”, telangiectatic/angiomatous lesions, xerosis, warts, tags, folliculitis, ulcers, dyshidrotic eczema, diffusely migratory but sometimes focally persistent patchy macular erythema), pruritus/itching (often diffusely migratory, sometimes aquagenic), flushing, angioedema, striae, dermatographism, hair thinning and alopecia, onychodystrophy (brittle nails, longitudinal ridges), poor healing of wounds-surgical and injury


  • Eyes: Irritated eyes, increased or decreased tearing, suffusion (looks like conjunctivitis, but doesn’t have inflammatory fluids), conjunctivitis, episodic difficulty focusing, lid tremor/tic (blepharospasm), solar sensitivity, infectious or sterile inflammation


  • Ears/Nose: Infectious or sterile otitis externa and/or media, hearing loss or hyperacusis, tinnitus, otosclerosis (abnormal bone growth inside the ear), dysosmia (disordered smell perception), coryza (runny nose), nasal or sinus or ear congestion


  • Mouth/Throat: Pain or irritation (sometimes “burning”), leukoplakia (white patches on mucous membranes of tongue/cheeks/etc), fibrosis (restricted mouth opening), lichen planus, ulcers, sores, angioedema, dental decay, dysgeusia (disordered taste perception), throat tickle/discomfort/irritation/pain, post-nasal drip


  • Lymph System: Enlarged lymph nodes, usually sub-pathologic and often waxing/waning in size, sometimes asymptomatic but not uncommonly tender, sometimes focal, sometimes migratory, pathology usually shows reactive lymphocytosis or sometimes an atypical non-specific lymphoproliferative disorder; left upper quadrant discomfort (likely from release of mediators from splenic mast cells with or without detectable splenomegaly)


  • Lungs and Upper Respiratory Tract: Rhinitis (runny nose and congestion), sinusitis, pharyngitis, laryngitis, bronchitis, pneumonitis (often confused with infectious pneumonia), cough, dyspnea (often low-grade, inconstant, “I just can’t catch a deep breath” despite normal pulmonary function tests), wheezing, obstructive sleep apnea, pulmonary hypertension


  • Heart and Vessels: Presyncope (lightheadedness, weakness, dizziness, vertigo) and/or syncope (patients may have been diagnosed with postural orthostatic tachycardia syndrome or neurocardiogenic syncope), hypertension and/or hypotension, palpitations, dysrhythmias, chest discomfort or pain (usually non-anginal in character), coronary and peripheral arterial atherosclerosis/spasm/infarction, idiopathic acute or chronic heart failure (e.g., takotsubo), aneurysms, hemorrhoids, varicosities (bulging areas of vessels), abnormal vessel development (hemangiomas, arteriovenous malformations, telangiectasias), migratory edema (often non-dependent and with normal cardiac and renal function)


  • Gastrointestinal: Aerophagia (swallowing excessive air), angioedema in any segment of the luminal tract, dysphagia-trouble swallowing (often proximal, possibly due to pharyngeal angioedema), bloating/gas, pain/inflammation (often migratory) in one or more segments of the luminal tract (from esophagitis (including eosinophilic), gastritis, ileitis, colitis, proctitis) and/or one or more solid organs (e.g., hepatitis, pancreatitis, cholecystitis), queasiness, nausea, vomiting (sometimes “cyclical”), diarrhea and/or constipation (often alternating), malabsorption (more often selective micronutrient malabsorption than general protein-calorie malabsorption), ascites either from portal hypertension and/or peritoneal serositis; gastroesophageal reflux disease (often “treatment-refractory”) and inflammatory/irritable bowel syndrome are common pre-existing diagnoses


  • Genitourinary: Inflammation (often migratory) in one or more segments of the luminal tracts (ureteritis, cystitis, urethritis, vaginitis, vestibulitis) and/or one or more solid organs (e.g., nephritis, prostatitis), interstitial cystitis, chronic kidney disease, endometriosis, chronic low back pain or flank pain or abdominal pain, hydronephrosis (likely from ureteral angioedema), infertility; in the appropriate setting of multisystem morbidity, miscarriages should prompt consideration of antiphospholipid antibody syndrome potentially due to Mast Cell Activation Disorders


  • Musculoskeletal: Clinical myositis (inflammation of muscles), often diffusely migratory (fibromyalgia is a common pre-existing diagnosis), subclinical myositis (i.e., asymptomatic elevated creatine kinase not otherwise explained), arthritis (typically migratory), joint laxity/hypermobility (patients may have been diagnosed with Ehlers-Danlos Syndrome Type III), osteoporosis/osteopenia, osteosclerosis, sometimes mixed osteoporosis/osteopenia/osteosclerosis; MCAD-driven musculoskeletal pain is not uncommonly poorly responsive to non-steroidal anti-inflammatory drugs and narcotics

  • Neurologic: Headache (especially migraine), presyncope and/or syncope, peripheral (usually distal) sensory and/or motor neuropathies including paresthesias, tics, tremors (typically resting), restless legs, chronic inflammatory demyelinating polyneuropathy, seizure disorders (can be “treatment-refractory”), pseudoseizures, dysautonomia


  • Psychiatric: Mood disturbances (e.g., anger, depression), bipolar affective disorder, attention deficit-hyperactivity disorder, post-traumatic stress disorder, anxiety and panic, psychoses, memory difficulties, word-finding difficulties, other cognitive dysfunction (brain fog), wide variety of sleep disruptions


  • Endocrinologic and Metabolic: Abnormal electrolytes (including magnesium) and liver function tests, delayed puberty, dysmenorrhea (painful periods), endometriosis, osteosclerosis and/or osteoporosis, hypothyroidism, hyperthyroidism, dyslipidemias (abnormal cholesterol levels), high ferritin level, selective vitamin and/or other micronutrient deficiencies, weight change, possibly diabetes mellitus


  • Hematologic/Clotting/Bleeding: Polycythemia (high RBC count) or anemia (may be macrocytic, normocytic, or microcytic), leukocytosis or leukopenia, chronic (usually mild) monocytosis or eosinophilia or basophilia, thrombocytosis or thrombocytopenia, arterial and/or venous thromboembolic disease, “easy” bruising/bleeding; in mast cell activation syndrome the marrow usually does not show increased (or even flow-cytometrically aberrant) mast cells; marrow histology often read as normal or as unspecified myelodysplastic/myeloproliferative syndrome; standard cytogenetic studies are almost always normal or show culture failure. In Sickle Cell Anemia patients, approximately 15-20% have severe, recurrent pain crises, and often get some relief with stabilization of mast cells.


  • Immunologic: Type I, II, III and IV hypersensitivity reactions (allergies), increased risk for malignancy, autoimmunity, impaired healing, increased susceptibility to infection, inability to clear infection in a typical timeframe, chronic or recurrent infections, elevated or decreased levels of one or more isotypes of immunoglobulin; modest monoclonal gammopathy of undetermined significance (MGUS) not uncommon; Common Variable Immunodeficiency (CVID).

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