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Glossary of mast cell related terms: P-Z

Parasympathetic nervous system: Part of the autonomic nervous system.  Regulates digestion and other functions.

Prostaglandin D2 (PGD2): The dominant prostaglandin produced by mast cells.

9a,11b-PGF2: a breakdown product of prostaglandin D2; can be measured to assess level of mast cell activation

Platelet activating factor (PAF): a mast cell mediator that correlates with severity of anaphylaxis; induces degranulation and release of leukotrienes and prostaglandins

Postural orthostatic tachycardia (POTS): increase of 30 bpm or more when standing in the absence of orthostatic hypotension.

Premedication: taking medication in advance of an event in order to suppress an undesirable reaction during the event, such as premedicating before surgery

Pre-stored: as relates to mast cell biology, mediators that are made inside the cell and stored in granules to be released at a later time

Progenitor cell: a cell that develops into another type of cell

Proliferation: growth and expansion of a cell population

Prostaglandin: a type of eicosanoid with wide ranging biological effects; PGD2 is the prostaglandin most abundantly produced by mast cells

Protracted anaphylaxis: a long episode of anaphylaxis symptoms despite treatment

Rare disease: a disease that affects only a small amount of people in a population; in the US, defined as affecting 200,000 people or less in the US

Rebound: a resurgence of symptoms after quelling symptoms earlier

Receptor: a protein on the outside of cells that bind specific molecules, causing a specific action to occur

Secretion: the release of molecules from inside the cell to the outside environment without degranulation

Sensitization: production of IgE specific to an allergen without obvious allergic reaction to the allergen

Serotonin: a neurotransmitter released by a number of cell types, including mast cells

Smouldering systemic mastocytosis (SSM): a form of SM in which organ damage and failure could eventually occur; diagnosed when someone with SM has two or more B findings

Splenomegaly: swelling of the spleen

Stem cell factor (SCF): a mast cell growth factor; SCF binds to CKIT and tells mast cells to stay alive and make more mast cells

Sympathetic nervous system: Part of the autonomic nervous system.  Controls the fight or flight response

Systemic mastocytosis (SM): a proliferative mast cell disease in which too many mast cells are produced

Systemic mastocytosis with associated clonal hematologic non-mast cell lineage disease (SM-AHNMD): co-occurrence of SM with another proliferative blood cell disorder, such as essential thrombocythemia or chronic myelogenous leukemia

Tachycardia: rapid heartbeat

Third spacing: when fluid is forced out of a place the body can use it and becomes trapped, such as ascites or angioedema

TLR: toll like receptor; receptors on the outside of many cells (including mast cells) that activate immune response to infections

Telangiectasia macularis eruptive perstans (TMEP): a less common form of cutaneous mastocytosis.  Found almost exclusively in adults.

Tryptase: a mast cell mediator; when tested outside of a symptomatic episode, it is used to measure the baseline amount of mast cells present ; when tested during a symptomatic episode, it can be used to identify mast cell activation

Urticaria pigmentosa (UP): also called maculopapular cutaneous mastocytosis (MPCM).  The most common form of cutaneous mastocytosis.

Urticaria: hives

Wheal and flare response: a reaction marked by redness and raised, taut skin due to histamine release

Glossary of mast cell related terms: M-O

Mast cell: white blood cells with important roles in allergy, anaphylaxis and immune defense that live in tissues and only briefly circulate in the blood; also called mastocytes

Mast cell activation: a change in mast cell behavior that occurs following exposure to a trigger that may indicate allergy or infection; a state in which mast cells release mediators, both through degranulation and through secretion; in some instances, culminating in anaphylaxis

Mast cell disease: a disease that occurs due to fundamental error in mast cell proliferation or activation physiology

Mast cell disorder: used synonymously with mast cell disease

Mast cell leukemia: a very aggressive mast cell disease marked by massively excessive proliferation of mast cells, culminating in progressive organ failure

Mast cell sarcoma: a very aggressive mast cell disease that presents as a connective tissue tumor and progresses to mast cell leukemia

Mast cell stabilizer: a medication that decreases the likelihood of mast cell degranulation and mediator release

Mastocytic enterocolitis: the phenomenon of having too many mast cells in the GI tract; originally described as more than 20 mast cells/ high power field, but there is no consensus on how many mast cells in a field is too many

Mastocytoma: a benign mast cell tumor. Most frequently occurs on skin, but can occur elsewhere in the body.

Mast cell activation disease (MCAD): usually a catchall term for mast cell diseases, although some people exclude cutaneous mastocytosis from this category

Mast cell activation disorder (MCAD): an alternate term for mast cell activation syndrome (MCAS); a non-proliferative mast cell disease that is usually diagnosed by detecting an elevation in mast cell mediators

Mast cell activation syndrome (MCAS): a non-proliferative mast cell disease that is usually diagnosed by detecting an elevation in mast cell mediators; occurs secondary to a known condition or idiopathically, in which no primary condition is identified; “primary” mast cell activation syndrome has its own name, MMAS

Mediator: a molecule released from a cell that has effects on the environment outside the cell; mast cells release dozens of mediators

Monoclonal mast cell activation syndrome (MMAS) : a mast cell disease diagnosed when a patient meets some criteria for SM but not enough for an SM diagnosed

Monophasic anaphylaxis: an anaphylactic event in which symptoms resolve following administration of medication and do not recur at a later time

Mutation: a change in the genetic sequence that can affect the way a gene is expressed, or in the way its gene product is made or functions

Myeloid: concerning cells that develop into granulocytes, monocytes, platelets or erythrocytes

Myeloproliferative neoplasm: a disorder caused by aberrant proliferation of a myeloid cell line, such as SM, myelofibrosis, essential thrombocythemia or polycythemia vera, among others

Neoplasm: an abnormal cell

N-methylhistamine: a breakdown product of histamine; can be tested for to assess mast cell activation

Oral allergy syndrome: An IgE reaction to raw fruits and vegetables that causes itching and swelling in the mouth and throat.

Orthostatic hypotension (OH): reduction of systolic blood pressure of more than 20 mm Hg or diastolic blood pressure of more than 10 mm Hg within three minutes of standing.

Orthostatic intolerance (OI): symptoms that occur when transitioning to a standing position

Glossary of mast cell related terms: F-L

FceRI: the high affinity IgE receptor; where IgE molecules bind to the outside of cells, like mast cells; binding the FceRI receptor triggers mast cell activation

Food associated, exercise induced anaphylaxis: An IgE mediated reaction that is triggered by ingesting certain foods in close time proximity to exercise

Food protein induced enterocolitis syndrome (FPIES): An allergic reaction to food proteins that is not mediated by IgE, usually found in infants; the most severe non-IgE mediated food hypersensitivity

Gastroparesis: a condition in which stomach contents are not emptied into the small intestine within an appropriate time period without an obvious anatomical explanation

Granule: a pocket inside a cell that holds molecules to be released outside of the cell

Granulocyte: white blood cells that have granules inside the cells that hold molecules to be released outside of the cell; mast cells, eosinophils, basophils and neutrophils are granulocytes

H1: histamine 1 receptor

H1 inverse agonist: a class of drugs that interferes with the effect of histamine at the H1 receptor

H2: histamine 2 receptor

H2 blocker: a class of drugs that interferes with the effect of histamine at the H2 receptor

Heparin: a mast cell mediator; a blood thinner

Hepatomegaly: swelling of the liver

Hepatosplenomegaly: swelling of the liver and spleen

Hereditary angioedema (HAE): a heritable blood disorder that causes episodes of protracted swelling that can be life threatening.

Histamine: a neurotransmitter; responsible for a large portion of symptoms seen in mast cell disease and anaphylaxis

HPA axis: the signals and feedback loops that regulate the activities of the hypothalamus, pituitary gland and adrenal glands to coordinate the body’s stress response; also helps regulate digestion, immune activation, sexuality and energy metabolism

Hypersensitivity: allergic reaction

Hypersplenism: overactivity of the spleen

IgE: an antibody that triggers allergic responses

Kounis Syndrome: an event in which a patient experiences severe chest pain or heart attack as the result of an allergic reaction; also called allergic angina or allergic myocardial infarction

Late onset anaphylaxis: Anaphylaxis that begins several hours after exposure to trigger

Leukotrienes: Structural class related to prostaglandins produced by the enzyme 5-lipoxygenase (5-LO); mediators released by mast cells.

Leukotriene receptor antagonist: A class of drugs that interferes with the function of leukotrienes; examples include montelukast and zafirlukast.

Ligand: a molecule that binds to another molecule, triggering a specific effect; with regards to mast cell disease, ligands bind to receptors, such as IgE (ligand) binding to FceRI (receptor)

LO: lipoxygenase; the enzyme that produces leukotrienes

Low histamine diet: a diet which minimizes dietary sources of histamine, which can help reduce symptoms for some mast cell patients; there is no authoritative list of low histamine foods and some trial and error is required


Glossary of mast cell related terms: A-E

Allergic march: the progressive accumulation of atopic conditions beginning in the first year of life; usually atopic dermatitis, allergic rhinitis, asthma, food allergy

Anaphylaxis: a rapidly progressing allergic reaction that involves multiple organ systems; can be fatal

Angioedema: Swelling caused when fluid leaves the bloodstream and becomes trapped between the deep dermis and subcutaneous tissue.

Anticholinergic: blocking the molecule acetylcholine from sending signals in the nervous system.  Many medications are anticholinergic, which can cause many side effects.

Ascites: free fluid in the abdomen; a form of third spacing

Aggressive systemic mastocytosis (ASM): a form of systemic mastocytosis in which mast cells invade organs, causing damage and dysfunction; diagnosed when a person meeting the criteria for SM has one or more C finding, criteria that indicate organ damage caused by mast cells

Asthma: inflammation of the airways causing swelling, narrowing and extra mucus production; can be allergic in nature

Atopy: tendency of a person to develop allergic diseases like asthma

Autoimmune disease: a disease caused when the immune system attacks healthy cells; mast cell diseases are not autoimmune diseases

Autonomic nervous system: a part of the nervous system that controls many involuntary functions of the body, including digestion.  It is composed of both the parasympathetic nervous system and the sympathetic nervous system.

B finding: criteria that indicate SM is progressing towards mast cells invading organs and damaging them; if 2 or more are present, smouldering systemic mastocytosis (SSM) is diagnosed

Biphasic anaphylaxis: Second episode of anaphylaxis symptoms after resolution

Bradykinin: a mediator released by mast cells that causes inflammation, pain and swelling

CD117: another name for CKIT receptor, found normally on the outside of mast cells

CD2: a marker not usually found on the outside of mast cells; an indicator of systemic mastocytosis; a cell adhesion molecule

CD25: a marker not usually found on the outside of mast cells; an indicator of systemic mastocytosis; part of a receptor for IL-2

CD34: a marker normally found on the outside of cells that become mast cells, and on new mast cells

Chronic urticaria: hives lasting longer than six weeks; can include angioedema

Circadian rhythm: the body’s internal clock

CKIT: a receptor on the outside of mast cells that binds stem cell factor, telling mast cells to stay alive and make more cells; is often mutated in systemic mastocytosis

Complement : a system of many small proteins circulating in the blood that can attack infectious agent ; can also cause angioedema

Cortisol : a steroid hormone produced by the adrenal glands ; critical in regulating stress response

COX : cyclooxygenase; enzymes that produce prostaglandins

Cutaneous mastocytosis (CM): infiltration of the skin by excessive mast cells.  The most common type of mastocytosis.

D816V/CKIT+: a specific mutation at codon 816 of the CKIT gene that causes the CKIT receptor to be misshapen so that mast cells get inappropriate signals to stay alive and keep making more cells

Darier’s sign: a wheal and flare response elicited by touching mast cell lesions; caused by histamine release

Desensitization: the elimination of the body’s allergic response to something

Diffuse cutaneous mastocytosis (DCM): The most severe presentation of cutaneous mastocytosis.  Lesions cover much of the body and may blister or bleed.

Deconditioning: when the body becomes acclimated to less physical stress and becomes less able to function properly under normal conditions.

Degranulation: the release of mediators stored in granules inside a cell; mast cell degranulation contributes to immune response as well as symptom profile in mast cell disease and anaphylaxis

Delayed food-induced anaphylaxis to meat: An IgE mediated reaction to beef, pork or lamb that occurs several hours after eating; caused by a tick bite inducing production of antibodies to carbohydrate a-gal.

Dysautonomia: fundamental dysfunction of the autonomic nervous system; there are many types, including POTS

Ehlers-Danlos Syndrome (EDS): a group of conditions caused by hypermobility and/or known genetic mutation affecting production of connective tissue components; Hypermobility EDS is seen disproportionately in the mast cell community

Edema: swelling; excess fluid trapped in tissues

Eicosanoid: the molecular class that includes prostaglandins and leukotrienes

Eosinophilia: elevation of eosinophils in the blood

Eosinophilic esophagitis: infiltration of the esophagus by eosinophils

Eosinophilic GI disease: IgE and delayed cell mediated reactions to foods caused by overactive eosinophils, affecting the GI tract.

Eosinophils: a granulocyte functioning similar to mast cells; mast cells and eosinophils can activate each other

Epinephrine: a hormone used to treat anaphylaxis

Exercise intolerance: diminished ability or inability to perform physical exercise; can be caused by a number of medical conditions