Glossary

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A
Aldosterone
A hormone produced by the cortex of the adrenal gland, which is instrumental in the regulation of sodium and potassium reabsorption by the cells of the tubular portion of the kidney.

Anaphylactoid reaction
A fast, systemic reaction that mimics anaphylaxis but which is not an IgE-mediated response. One difference is that a person can have an anaphylactoid reaction to something on the very first exposure -- sensitization is not required. In an anaphylactoid reaction, the person must usually be systemically exposed to a larger amount of a substance than would a person experiencing anaphylaxis. Allergy skin tests are not useful in predicting anaphylactoid reactions. Possible causes include medications, insect bites, exercise, blood products, and diagnostic testing materials. For more information.

Anaphylaxis
A life-threatening, usually rapid, immune-mediated systemic reaction. Informally called "shocking." Anaphylaxis can include any and all of the following symptoms:

Angioedema
Deep tissue swelling, most often of face, mouth, throat, neck, hands, or abdomen. Also referred to as Quinke's disease. See also hereditary angioedema.

Angiotensin
A family of peptides that act as vasoconstrictors to narrow blood vessels. There is an inactive form (angiotensin I) and two varieties (angiotensin II and angiotensin III) that elevate blood pressure and stimulate the adrenal cortex to secrete aldosterone.

Antiemetic
Medication that is used to suppress nausea or vomiting.

Antihistamine
Medications that relieve or prevent the symptoms caused by histamine that is released from mast cells and basophils. There are several types of histamine receptors; the ones of interest in mast cell disorder symptoms are H1 histamine receptors and H2 histamine receptors. Antihistamines that block the action of histamine at H1 histamine receptors are the ones that are used for allergic-type symptoms. These include Benadryl®, Atarax, Allegra®, and chlorpheniramine maleate. These antihistamines are divided into two categories: sedating, which can cause drowsiness in many people, and non-sedating, which do not cause drowsiness in most people. Antihistamines that block the action of histamine at H2 histamine receptors reduce the amount of acid released into the stomach and help to relieve itching. These include Zantac® (ranitidine), Tagamet® (cimetidine), and Pepcid® (famotidine).

Antihistamines, Classes of
There are six classes of antihistamines:
  1. Ethylenediamines: For example, pyrilamine (mepyramine), antazoline, methapyrilene, and tripelennamine
  2. Ethanolamines: For example, diphenhydramine, bromodiphenhydramine, carbinoxamine, clemastine, dimenhydrinate, diphenylpyraline, doxylamine, and phenyltoxamine
  3. Alkylamines: For example, brompheniramine, pyrrobutamin, desbrompheniramine, tripolidine, dexchlorpherniramine, chlorpheniramine, dimethindene, and pheniramine
  4. Phenothiazines: For example, promethazine, methdilazine, and trimeprazine
  5. Piperazines: For example, cyclizine, buclizine, chlorcyclizine, hydroxyzine, meclizine, and thiethylperazine
  6. Piperidines: For example, cyproheptadine and azatadine

The ethylenediamines, for instance, will often cause GI symptoms and some sedation. The ethanolamines have anticholinergic effects; one of them, dimenhydrinate, is used as an antiemetic or to control motion sickness. Diphenhydramine is available as an over-the-counter sleeping preparation. The alkylamines are potent when used in small doses; while well tolerated, they have a more sedative effect. The phenothiazines also have marked anticholinergic effects and a strongly sedative effect as well. The piperazines are used to treat motion sickness; hydroxyzine is often used as a tranquilizer. For more info.

Antinuclear antibodies (ANA)
Unusual protein antibodies, detectable in the blood, that have the capability of binding to certain structures within the nucleus of the cells. ANA are seen in 96% of those with Systemic Lupus Erythematosus (SLE), in 5% of healthy individuals, and in many patients with autoimmune diseases. A titer of 1:80 or above is usually considered positive.

Apoptosis
This refers to the normal death of cells that are no longer needed by the body. In apoptosis, the contents of the cell are not spilled into the surrounding tissue, unlike the other type of cell death, necrosis.

Arrhythmia
Irregularity in the rhythm of the heartbeat.

Assay, Complement
See complement.

Aseptic necrosis
See avascular necrosis.

Asthma
A disorder of respiration, characterized by bronchospasm, wheezing, and difficulty in expiration (breathing out), often accompanied by coughing and a feeling of constriction in the chest. Asthma usually has a sudden onset, and it can be caused by allergenic reactions. Also called bronchial asthma. For more information.

Autoimmune
Relating to the immune response of an organism against any of its own tissues, cells, or cell components.

Avascular necrosis
A disease that results from temporary or permanent loss of blood supply to the bones. Without blood, the bone tissue dies and can cause the bone to collapse. If bones near a joint are involved, it often leads to collapse of the joint surface. This disease also is known as osteonecrosis, aseptic necrosis, or ischemic bone necrosis. For more information, see the National Institute of Arthritis and Musculoskeletal and Skin Diseases web page, "Questions and Answers about Avascular Necrosis."

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B
Basophil
A type of white blood cell; basophils release histamine and leukotrienes as well as other active chemicals and messenger molecules, and may be involved in allergic reactions.

Bi-phasic reaction
The return of symptoms several hours after an attack has ended. This can happen with anaphylaxis, and the second attack often takes the person by surprise.

Bone marrow biopsy (BMB)
Bone marrow is soft tissue found inside some of the larger bones in the body. A bone marrow biopsy is the removal of a sample of this tissue with a needle for examination under a microscope. For more information.

Bronchodilation
The relaxation of the muscular lining of the bronchi, causing an increase in the flow of air when breathing.

Bronchospasm
The spasmodic contraction of the muscular lining of the bronchi, causing difficulty in breathing.

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C
Catarrh
More commonly known as a "runny nose," catarrh is inflammation of mucous membranes in the respiratory tract, which in turn produce excessive secretions.

C1 esterase inhibitor
See C1 inhibiting factor.

C1 inhibiting factor
A test that measures the concentration of an inhibitor of complement in the blood. Also called C1 esterase inhibitor.

Carcinoid
A small, yellowish amino acid- and peptide-secreting tumor usually found in the gastrointestinal tract and lung.

Carcinoidosis
See carcinoid syndrome.

Carcinoid syndrome
The systemic effects — which include flushing, palpitations, diarrhea, and cramps — resulting from increased blood levels of serotonin secreted by a carcinoid. Also called carcinoidosis. For more information.

C-kit mutation
Refers to the detection of a specific mutation in the gene for the mast cell c-kit receptor. This is one of the minor criteria used for a diagnosis of mastocytosis.

C-kit receptor
A protein on the surface of some cells that binds to stem cell factor, which is a substance that causes certain types of cells to grow.

Colitis
Inflammation of the colon.

Complement
Complement activity (CH50, CH100, terminal complement component, or individual complement proteins) is measured to determine if complement is involved in the development of a number of diseases. Complement activity is also measured to monitor how severe a disease is or to determine if treatment is working. Also called complement assay or complement proteins.

Corticosteroids
Anti-inflammatory medications, also known as glucocorticoids or "steroids," that reduce the production of inflammation-causing signals from immune system cells. These medications can have negative health consequences with long-term use (avascular necrosis, osteoporosis, diabetes, Cushing's Syndrome, etc.). These medications are not the same as the anabolic steroids that are misused by some athletes to increase their performance.

COX
Designates cyclo-oxygenase enzymes, which are needed for various bodily functions, such as converting arachidonic acid into prostaglandins. COX-1 has been described as a "maintenance" or "housekeeping" enzyme, in contrast to COX-2, which has been described as "inflammatory."

Cushing's syndrome
A condition characterized by abnormal accumulations of facial and trunk fat, fatigue, hypertension, and osteoporosis, which is caused by hyperfunction of the adrenal cortex or by long-term administration of corticosteroids. Also called Cushing's disease. For more information.

Cutaneous
Pertaining to or affecting the skin.

Cutaneous mastocytosis (CM)
Mastocytosis that occurs more locally, in the skin, appearing as a spotted rash (urticaria pigmentosa).

Cytometry
See flow cytometry.

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D
Darier's sign
A clinical sign in which stroking of the skin results in redness and swelling in people who have urticaria pigmentosa.

Degranulation
The process of a cell losing its granules, which are the stored products of the cell's metabolic activity. This occurs in mast cells, basophils, neutrophils, eosinophils, and platelets when secretory products are released from the granules.

Diabetes
A disorder of carbohydrate metabolism, characterized by inadequate production or utilization of insulin and resulting in excessive amounts of glucose in the blood and urine, excessive thirst, weight loss, and in some cases progressive destruction of small blood vessels leading to such complications as infections and gangrene of the limbs or blindness. Also called diabetes mellitus. For more information see the National Diabetes Association web site.

Diastolic blood pressure
The arterial blood pressure between heartbeats. This is the lower number in someone's blood pressure.

Disease, Cushing's
See Cushing's syndrome.

Duodenitis
Inflammation of the duodenum, which is the part of the small intestines just below the stomach.

Dysphonia
Disturbance of normal vocal cord function — difficulty in speaking.

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E
Edema
Swelling as a result of the escape of fluids from their natural vessels into the spaces between cells and tissues or into bodily cavities. Also spelled oedema.

Eosinophil
A white blood cell that contains granules filled with chemicals that are damaging to parasites and enzymes that damp down inflammatory reactions.

Eosinophilic enteropathy
A disorder of the digestive system in which too many eosinophils — a type of white blood cell — are found in one or more specific places in the digestive system. For more information, see the American Partnership for Eosinophilic Disorders (APFED) site.

EpiPen®
Brand name for an epinephrine auto-injector, which is available by prescription and is used to treat anaphylaxis or severe mast cell attacks. For more info, see EpiPen.com.

Erythema
Redness, flushing.

Esophagitis
Inflammation of the esophagus, the tube connecting a person's mouth to his or her stomach.

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F
Flow cytometry
A process in which cells with some specific characteristics are detected and counted by an automated device through which the cells pass in single file, as a fluid stream.

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G
Gastroenteritis
Inflammation or irritation of the stomach or intestine.

Gastroesophageal Reflux Disease (GERD)
Gastroesophageal reflux is the term used to describe a backflow of acid from the stomach into the esophagus. The usual symptom is heartburn, an uncomfortable burning sensation behind the breastbone, often after a meal. Also called reflux, reflux esophagitis, or (inaccurately) hiatus hernia. For more information.

Gold standard
Ideal instance. For example, it has been said that the bone-marrow biopsy is the gold standard for mastocytosis diagnosis.

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H
H1
See histamine H1 receptors.

H2
See histamine H2 receptors.

H3
See histamine H3 receptors.

Heparin
A natural substance, occurring in various bodily tissues, especially the liver, which inhibits blood clotting.

Hereditary angioedema (HAE)
A genetic form of angioedema in which people are born lacking C1 esterase inhibitor, an inhibitor protein, that normally prevents activation of a cascade of proteins leading to the swelling seen in angioedema. People with HAE can develop recurrent attacks of swollen tissues, pain in the abdomen, and swelling of the voice box, which can compromise breathing. The diagnosis is suspected with a history of recurrent angioedema. It is confirmed by finding abnormally low levels of C1 esterase inhibitor in the blood. Treatment options include antihistamines and male steroids (androgens) that can also prevent the recurrent attacks. It is also called hereditary angioneurotic edema. US Hereditary Angioedema Association.

Histamine
Histamine is a chemical that is released by cells during an allergic reaction. Histamine is one of the substances responsible for the symptoms on inflammation and is the major reason for running of the nose, sneezing, and itching in allergic rhinitis. It also stimulates production of acid by the stomach and narrows the bronchi or airways in the lungs.

Histamine receptors
Cell-surface proteins that bind histamine and trigger intracellular changes influencing the behavior of cells. Histamine receptors are widespread in the central nervous system and in peripheral tissues. Three types have been recognized and designated H1, H2, and H3. They differ in pharmacology, distribution, and mode of action.

Histamine H1 receptors
A class of histamine receptors that mediate smooth muscle contraction, increased vascular permeability, hormone release, and cerebral glyconeogenesis.

Histamine H2 receptors
A class of histamine receptors that mediate gastric acid secretion, smooth muscle relaxation, inotropic and chronotropic effects on heart muscle, and inhibition of lymphocyte function.

Histamine H3 receptors
A class of histamine receptors that were first recognized as inhibitory autoreceptors on histamine-containing nerve terminals and have since been shown to regulate the release of several neurotransmitters in the central and peripheral nervous systems.

Hypotension
A decrease in blood pressure.

Hypertension
An increase in blood pressure.

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I
Idiopathic
A term that used to describe a disease or condition of unknown cause or origin.

Idiopathic anaphylaxis (IA)
A form of anaphylaxis with no identifiable external allergen or stimulus. (Note: Some people with known allergens or triggers are also classified as having IA if it is believed that these are insufficient to explain the frequency or intensity of reactions to them.)

Immunoglobulin
Any of several classes of structurally related proteins (IgA, IgD, IgE, IgG, or IgM) that function as antibodies and are found in plasma and other body fluids as well as in the membrane of certain cells.

IgA (immunoglobulin A)
A class of antibodies found in respiratory and alimentary tract secretions and in saliva and tears, functioning as the body's first line of defense against invading foreign substances by neutralizing viral antigens and by preventing the adherence of bacteria to mucous membrane surfaces.

IgD (immunoglobulin D)
A class of antibodies present as antigen receptors on most cell surfaces and predominant on human type B cells.

IgE (immunoglobulin E)
IgE, which is present primarily in the skin and mucous membranes, is one of the five major classes of immunoglobulins. IgE is a trace serum protein (antibody) associated with allergic reactions.

IgG (immunoglobulin G)
A class of circulating antibodies predominant in serum, which are produced by plasma and memory cells in response to pathogens and other foreign substances. They are able to pass through the placental wall into the fetal circulation to impart immune defense for the developing child.

IgM (immunoglobulin M)
A class of short-term circulating and secretory antibodies that exist as an aggregate of five antibody molecules, which have a high affinity for viruses.

Interstitial cystitis (IC)
A chronic inflammation of the bladder wall leading to frequent, painful urination. IC can lead to scarring and stiffening of the bladder, decreased bladder capacity, and in rare cases, ulcers in the bladder lining. Symptoms of IC include urinary urgency and frequency, difficulty in urinating, small urine output, pain in the bladder and/or urethra that is temporarily relieved by voiding. In some patients, pain may radiate to the genitals, rectal area, and thighs. Urine cultures are negative. Cystoscopic examination of the bladder and hydrodistention under general anesthesia reveal petechial hemorrhages or glomerulations on the bladder wall in 90% of people with IC, while 10% exhibit Hunner's patches or ulcers. IC is also known as "painful bladder syndrome." For more information, see the Interstitial Cystitis Association's web page, "What Is IC?"

Ischemic bone necrosis
See avascular necrosis.

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J
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K
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L
Laryngeal edema
Swelling in and around the vocal cords.

Larynx
Vocal cords, also known as the "voice box." Laryngeal is the descriptive form of this term.

Leaker
This is a slang term used by some who have a mast cell disease to refer to someone who experiences the symptoms of systemic release of mast cell mediators, but not anaphylaxis, as in "I'm a leaker -- not a shocker."

Leukotrienes
Potent chemicals released by mast cells, basophils, eosinophils, and other types of cells. Leukotrienes are involved in causing inflammation, contraction of smooth muscles such as in the airway, and leakage of fluids from blood vessels into the surrounding tissues. Leukotrienes are produced in mast cells from a chemical called arachidonic acid, which is stored in mast cells and can be recognized by the presence of clear "bubbles" within the cell. They are involved in asthma, urticaria, and bowel inflammation as well as other inflammatory processes.

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M
Mast cell
A large connective tissue cell that contains inflammatory biochemicals such as histamines (H1 and H2), leukotrienes, prostaglandins, heparin, and serotonin, which are released in allergic reactions or in response to injury or inflammation. Mast cells are meant to help defend against parasites (as opposed to bacteria or viruses). They are bound within tissues that interface with the external world such as the skin, respiratory or intestinal tract and do not circulate through the body. The mast cell has binding sites on its surface for a special type of antibody called IgE.

Mast cell activation disorder/syndrome (MCAD/MCAS)
A disorder or syndrome in which there is evidence of the systemic, inappropriate release of mast cell mediators. While people with MCAD/MCAS have a normal or near-normal tryptase level and a bone marrow biopsy that contains a normal number of mast cells, they experience most of the same symptoms as does someone with mastocytosis. Idiopathic anaphylaxis is a subcategory of MCAS/MCAD.

Mast cell degranulation
See degranulation

Mast cell stabilizers
Non-steroidal medications that reduce the release of chemicals from mast cells. They include sodium cromoglycate (cromolyn), nedocromil, and ketotifen.

Mastocytoma
A nodule of mast cells, mastocytomas can involve the skin, subcutaneous tissue, and sometimes muscle. Mastocytomas are rare and are mostly seen in pediatric patients within the first 3 months of life. A solitary mastocytoma is a single lesion. Also called a mast cell tumor.

Mastocytosis
A rare disease characterized by the presence of too many mast cells in various organs and tissues. The condition can be a chronic, long-term illness or it can develop suddenly. Mastocytosis may be systemic, involving a variety of organs, or cutaneous, also referred to as urticaria pigmentosa.

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N
Necrosis
Death of animal or plant tissue. See also avascular necrosis.

Neoplasm
New growth of abnormal cells; a tumor. Neoplastic cells represent a clone, meaning that all the involved cells are derived from a single, abnormal cell that may reproduce in an uncontrolled fashion, sometimes rapidly. A neoplasm may be benign or malignant.

NSAIDs
Abbreviation for Non-Steroidal Anti-Inflammatory Drugs, which are used to treat muscle and joint inflammation and pain. Traditional NSAIDs, like ibuprofen (Motrin, Advil) and naproxen (Naprosyn, Alleve), inhibit both COX-1 and COX-2 prostaglandins. Many of the undesirable side effects of using these non-selective NSAIDs result from inhibiting the COX-1 "maintenance" prostaglandins. The beneficial effects of the newer NSAIDs, like Celebrex and Vioxx, result from inhibiting, or limiting, only the COX-2 "inflammatory " prostaglandins. These specific NSAIDs are effective for treatment of musculoskeletal pain and are without many of the side effects associated with the traditional agents. Many people who have mast cell-related diseases cannot take NSAIDs or are allergic to them. For more info.

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O
Oedema
See edema.

Osteonecrosis
See avascular necrosis.

Osteoporosis
A disorder in which the bones become increasingly porous, brittle, and subject to fracture, due to loss of calcium and other mineral components. Osteoporosis sometimes results in pain, decreased height, and skeletal deformities. It is common in older persons, primarily postmenopausal women, but it also associated with long-term steroid therapy, certain endocrine disorders, and mastocytosis.

OTC
Abbreviation for over the counter, a term used to describe medications that are available without a prescription.

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P
Pallor
Becoming very pale.

Palpitation
An abnormally rapid or violent beating of the heart.

Paucicellular mastocytosis
See Telangiectasia macularis eruptiva perstans (TMEP).

Prostaglandins
Types of lipid fatty acids produced by the body, some of which cause inflammation and contribute to the brain’s perception of pain. They are called local hormones because they act where they are produced. There are two kinds of prostaglandins, and the body has problems when both types are inhibited. "Maintenance" prostaglandins are made regularly by the body by an enzyme called cox-1, and they play a role in maintaining normal function in some systems within the body. Examples include the protective lining of the stomach, normal platelet function, and blood flow to the kidneys. "Inflammatory" prostaglandins are produced by an enzyme called cox-2 in response to an inflammatory stimulus, and they play a role in causing inflammation and pain.

Prostaglandins D2 (PGD2)
A major product of mast cells that is released in large quantities during allergic and asthmatic anaphylaxis. People who have mastocytosis produce excessive amounts of PGD2, which causes vasodilation, flushing, hypotension, and syncopal episodes.

Prostaglandins E2 (PGE2)
Actions include: Bronchodilation, vasodilatation, stimulation of intestinal fluid secretion, and relaxation of gastrointestinal smooth muscles.

Proteins, Complement
See complement.

Pruritus
Itching.

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Q
Quinke's disease
See angioedema.

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R
RAST
A radioallergosorbent test (RAST) is an allergy test performed on a sample of blood. A RAST can be performed when a more common allergy skin test cannot be done -- for example, when a person has a skin condition or cannot stop taking antihistamines long enough to have allergy skin tests done. A skin test is more sensitive, less expensive and produces immediate results. For more information on RAST.

Receptors, Histamine
See histamine receptors.

Rhinitis
Inflammation of the nose or its membranes, resulting in "a runny nose."

Rhinorrhea
Excessive mucus discharge from the nose.

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S
Sedimentation rate (SED rate)
A test that measures the precipitation of red cells in a column of blood. High rates of precipitation (a "high SED rate") usually indicate increased disease activity.

Serotonin
A neurotransmitter that is involved in sleep, depression, and memory, among other neurological processes.

Shock
Bodily collapse or near-collapse due to inadequate oxygen delivery to cells. Shock is characterized by pallor, tachycardia, reduced cardiac output, and circulatory insufficiency.

Shocker
This is a slang term used by some who have a mast cell disease to refer to someone who experiences anaphylaxis, as in "I'm a shocker." Compare to leaker.

Solitary mastocytoma
A single nodule or tumor of mast cells.

Stabilizer, Mast cell
See mast cell stabilizer.

Syncope
Fainting or faintness.

Systemic
Affecting the body as a whole.

Systemic mastocytosis
Mastocytosis involving a variety of organs.

Systolic blood pressure
The maximum arterial pressure due to the contraction of the heart. This is the higher number in someone's blood pressure.

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T
Tachycardia
An abnormally rapid the heart rate.

Telangiectasia macularis eruptiva perstans (TMEP)
A rare form of urticaria pigmentosa (UP) that occurs mostly in adults. TMEP lesions are diffuse red patches approximately 2 to 6 mm in diameter and without sharply demarcated borders. The lesions, which are not itchy, are associated with overlying telangiectasis (dilated capillaries).

Tryptase, Serum
Serum tryptase level is used as a diagnostic marker in mastocytosis and is considered to reflect the burden (number) of (neoplastic) mast cells.

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U
Urticaria
An allergic reaction in the skin that is characterized by pale or red irregular, elevated patches and that is usually accompanied by severe itching — hives.

Urticaria pigmentosa (UP)
Condition characterized by many small, reddish-brown, bumpy areas on the skin, ranging from just a few to thousands.

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V
Vasoconstriction
The compression or shrinking of blood vessels, as by the action of a nerve or a drug.

Vasoconstrictor
A nerve or drug that causes vasoconstriction.

Vasodilation
The expansion or opening up of blood vessels, as by the action of a nerve or a drug.

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W
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X
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Y
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Z
Zollinger-Ellison syndrome
A rare disorder that causes tumors in the pancreas and duodenum and ulcers in the stomach and duodenum. For more information.

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Are there medical or scientific terms related to mast cell diseases that you do not understand? We're always looking for new terms to add to our glossary. Please send your suggestions to: Candace Van Auken.

Our thanks go to Gay Buchanon for providing a list of terms to add to the glossary, and to Nancy Gould for reviewing and editing the entries.

This page was last updated on June 8, 2004.