Terminology & Definitions

 504 Programs

Section 504 of the Rehabilitation Act of 1973 provides children with disabilities opportunities for success in school when given appropriate accommodations.


A state of shock, as in an extreme allergic reaction. Systemic anaphylaxis, which produces peripheral vasodilation, bronchospasm, and laryngeal swelling, can be life threatening. In mastocytosis, anaphylaxis can be caused by allergic reactions or by direct triggers of mast cell mediator release.


Pain originating in the chest that is caused by a reduction of blood flow to the heart muscle.


That which counteracts the action of something else.

Antagonist drug

A drug that prevents receptor stimulation. An antagonist drug has an affinity for a cell receptor, and by binding to it, prevents the cell from responding to an agonist. Example: Antihistamines are antagonist drugs that prevent cells in the body from responding to the histamine released by mast cells.


A drug that opposes the action of histamine. The drug does not prevent the mast cells from releasing histamine, but the drug competes for the same receptor sites as histamine on receptor cells, blocking histamine’s ability to bind to those sites, preventing or reducing the symptoms.


An H1 antihistamine, often prescribed to relieve symptoms of mastocytosis. Generic name: Hydroxyzine hydrochloride.


A kind of white blood cell that is essential to the nonspecific immune response to inflammation because of its role in releasing histamine and other chemicals that dilate blood vessels.


Not progressive, nonmalignant, not cancerous.

Biopsy, Bone marrow

The removal of a thin strip of tissue from the interior of one of the flat bones, usually from the hip bone near the spine. Blood cells and mast cells are produced in the bone marrow. The removed tissue is examined microscopically to determine the state of blood cell and mast cell formation.

Biopsy, Skin

The removal of a piece of skin in order to microscopically study its structure. In mastocytosis of the skin, diagnostic infiltrations of mast cells are present.


A large blister or skin vesicle filled with fluid.


Like a blister or vesicle.


A hormone produced by the adrenal gland that regulates the metabolism of fats, carbohydrates, sodium, potassium, and proteins, and is also used as an anti-inflammatory agent.

Cromolyn sodium

A mast cell stabilizer often prescribed to relieve symptoms of mastocytosis. Brand names: Gastrocrom®, Nalcrom®, Intal®, Nasalcrom®.


Relating to the skin.

Darier's sign

[Ferdinand Jean Darier, French dermatologist, 1833–1916.] The skin change produced when the skin lesion in urticaria pigmentosa is briskly rubbed. The area usually begins to itch, becomes raised and surrounded by erythema.


Discharge of the contents of granules inside a cell, releasing chemical mediators into the tissue.


A form of hive in which redness and a wheal appear on the skin along the path of gentle stroking or scratching.


Condition in which the skin becomes red and raised when the skin is scratched lightly or irritated.

Diffuse cutaneous mastocytosis

A form of mastocytosis of the skin in which all the skin is involved in excessive mast cell infiltration.


Difficulty in breathing.


Swelling, body tissues containing an excessive amount of tissue fluid.


A proprietary form of epinephrine supplied in a ready-to-inject form.


Reddening of the skin caused by dilation of superficial blood vesels in the skin.


To blush; to become red.

H1 antihistamine

Agents that block the action of histamine on H1 receptors, helps relieve itching and flushing, examples are hydroxyzine hydrochloride (brand name: Atarax), diphenhydramine (Benadryl®).

H2 antihistamine

Agents that block the action of histamine on H2 receptors. When added to an H1 antihistamine, it may help control itching and whealing in addition to gastrointestinal symptoms, examples are ranitidine (brand name Zantac®) and cimetidine (Tagamet®).


Pertaining to the production or development of blood cells.


A mediator released by mast cells and basophils that causes dilation of blood vessels, increased secretion of acid by the stomach, smooth muscle constriction, and mucus production, tissue swelling, and itching.

Hydroxyzine hydrochloride

An H1 antihistamine frequently prescribed to treat symptoms of mastocytosis. Brand name: Atarax.


Increased pigmentation.


Excessive proliferation of normal cells in the normal tissue arrangement of an organ, with consequent enlargement of the affected part. Adjective: hyperplastic.


A decrease in blood pressure to below normal.


Inactive, not aggressive.


An area of hardened tissue.


A change in tissue structure caused by injury or disease.


A flat spot on the skin whose color may be lighter or darker than the surrounding skin.

Magic Masto Lotion

An unofficial topical preparation containing 1% cromolyn; used to reduce itching and inflammation on the skin.


Not getting enough nutrient from the gastrointestinal tract.


A sense of discomfort, weakness, or fatigue; feeling run down.


Growing worse; resisting treatment; tending or threatening to produce death.

Mast cell leukemia

A rare and aggressive form of adult mastocytosis in which death occurs within a short time.

Mast cell stabilizer

A drug that helps reduce the sensitivity of mast cells, to slow down their release of mediators, reduce diarrhea, flushing, head aches, vomiting, urticaria, abdominal pain, nausea, and itching, examples are cromolyn sodium (Gastrocrom®, Nalcrom®) and ketotifen.


A localized overgrowth of mast cells in an area of skin. It is raised, pink, and may have a blistered surface, especially if rubbed.

The Mastocytosis Society

A not-for-profit organization in the United States that is dedicated to education about and finding a cure for mastocytosis.


Any substance or structure that transmits information between two reagents, cells, tissues or organs. Histamine is a mediator. It is released from mast cells and causes a reaction in surrounding cells that results in allergic type symptoms.

Medic Alert®

A non-profit organization that provides a bracelet or pendant with an emblem on which is contained crucial information about a patient’s medical history and a warning in case of emergency. The company also keeps a file of the medical information and provides an emergency phone number that medical personnel may call free of charge.


A melanin-forming cell. Melanin is the pigment that gives color to hair and skin.


An abnormal new growth of tissue; tumor.


Pertaining to or being a neoplasm.


A small bump or pimple that rises above the surface of the neighboring skin.


A raised patch on the skin or on a mucous membrane surface.

Plasma cell

A type of white blood cell formed from the bone marrow, that has been sensitized to a specific foreign antigen and produces antibodies to that particular antigen.


Round or oval discs found in the blood that are fragments of large cells (megakaryocytes) found in the bone marrow. They play an important role in blood clotting, and control of bleeding.


A glucocotricosteroid with the same effects as cortisone; regulates the metabolism of fats, carbohydrates, sodium, potassium, and proteins, and is also used as an anti-inflammatory agent.


Any of a large group of local short-range hormones that are formed quickly, act in the immediate area, and then decay or are destroyed by enzymes. They are important mediators of inflammation. Nonsteroidal anti-inflammatory drugs block the production of prostaglandins.


Itching, tingling or faintly burning skin sensation that prompts a person to scratch.


Psoralin with Ultra-Violet-A — A skin treatment that combines an oral medication (psoralens) with exposure of the skin to light in the ultra-violet part of the spectrum. It is sometimes used to temporarily reduce urticaria pigmentosa rash.


A discharge from the nose.


Fainting; transient (and usually sudden) loss of consciousness.


Affecting the entire body.

Systemic mast cell disease

Sometimes used as a synonym for systemic mastocytosis; a form of mastocytosis in which one or more internal organ systems is infiltrated by a pathologic increase in mast cell numbers.


Abnormally rapid heart rate.


The Mastocytosis Society


Something that prompts or causes a reaction or allergic response.


A type of mediator released from the mast cell.


Multiple swollen raised areas on the skin that are intensely itchy; not to be confused with urticaria pigmentosa, which is one of the forms of mastocytosis.

Urticaria Pigmentosa

A skin form of mastocytosis characterized by the presence of brown macules or papules that often form a hive and become red when stroked or scratched. (Also called Cutaneous Mastocytosis)


A burning or itching sensation.


A second-generation H1 antihistamine, derived from hydroxyzine hydrochloride.