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Glossary of psoriasis related terms

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acitretin: A synthetic derivative of vitamin A that is taken orally. It is indicated for severe psoriasis.

angiogenesis: The process of the growth and development of new blood vessels in the body. Alterations in the blood vessel formation of the skin are a prominent feature of psoriasis.

antibody: A protein made by white blood cells in the immune system. These proteins move through the blood stream looking for and attaching to foreign materials - such as viruses and bacteria - in order to neutralise them.

antigen: A substance that, when introduced into the body, signals the immune system to produce antibodies. Viruses, bacteria, and toxins may all act as antigens.

apoptosis: Programmed cell death; a mechanism where the destruction of cells is used to regulate the cellular populations.

arachidonic acid: A fatty acid found in high concentrations in the skin of people with psoriasis, suggesting that it could be one of the factors that contributes to inflammation and cell proliferation.

autoimmune disease: A disease in which autoantibodies or lymphocytes attack other molecules, cells, or tissues within the body; the body launches an immune response against its own tissue. Psoriasis is widely believed to be an autoimmune disease, as is psoriatic arthritis.


B cell: A type of white blood cell involved in the production of antibodies. These cells are produced in bone marrow.

beta-blockers: Medications that are commonly prescribed for lowering blood pressure, relieving angina, or treating congestive heart failure. These drugs are thought to trigger or aggravate psoriasis in some people.

biologicals: Medications that are made using living organisms or their products. For the treatment of psoriasis, biologics are available that specifically target the immune system and help lessen the symptoms of the disease.

broadband light therapy: A type of light therapy that may be used for the treatment of psoriasis. The treatment offers a broad range of UVB light (280nm to 315nm).


calcipotriene (or calcipotriol): A synthetic form of vitamin D3, used topically to treat plaque psoriasis.

cataract: Clouding of the lens of the eye, which leads to vision loss. Patients receiving PUVA treatment must be especially careful to protect their eyes during and immediately after treatments.

cell: The smallest unit of an organism that is capable of sustaining life. Cells are the building blocks of all living things.

chimera: A protein or an organism that consists of genetic material from two or more different species.

chimeric monoclonal antibody: A monoclonal antibody composed of the variable region of a murine antibody and the constant region of human antibody.

chromosomes: Structures found in the nucleus of a cell that are made up of double-stranded DNA and proteins. Chromosomes carry genes that determine specific traits and can pass the traits from one generation to the next. Several studies suggest some susceptibility to psoriasis may be inherited.

chronic: A condition that is marked by long duration or frequent recurrence.

coal tar: Tar distilled from bituminous coal applied to the skin to treat psoriasis. Often used with UV light therapy.

collagen: The fibrous protein that makes up skin, cartilage, bone, and other connective tissue in the human body.

corticosteroid: A synthetic hormone similar to that produced naturally by the adrenal glands which is available in pill, topical, and injectable forms.

CDR: The complementarity determining region (CDR) of an antibody or a T lymphocyte receptor determines its specificity and is the point of contact with a specific ligand.

cirrhosis: A disease characterised by the buildup of scar tissue and nodules in the liver that interfere with its function.

clone: A genetically identical progeny produced by the natural or artificial reproduction of an organism, cell or gene.

cyclosporine: A medication originally developed to prevent the immune system from rejecting transplanted organs, which has also proved helpful in treating psoriasis.

cytokines: Proteins secreted by various types of cells and involved in cell-to-cell communication during immune responses.

cytotoxicity: The quality of being toxic to cells. Certain drugs may be produce cytotoxic effects.


dendritic cells: These cells function to obtain antigen in tissues, they then migrate to lymphoid organs and activate T cells. They are required for a specific immune response.

dermatitis: Inflammation of the skin that may result in redness or itching.

dermis: The layer of skin that is just below the epidermis.

dithranol: A topical treatment which may be prescribed for uncomplicated mild to moderate psoriasis.

DLQI: The Dermatology Life Quality Index (DLQI) is a simple 10-question validated Quality of Life questionnaire used widely internationally.

DNA: The abbreviation for deoxyribonucleic acid, which carries genetic information in cells.


eczema: An inflammatory disease of the skin, characterised by oozing, crusting, and/or scaling. There is also an eczema-type psoriasis, which is most common on the hands and feet and is characterised by itchiness, inflammation, and painful cracks in the skin.

emollient: An agent that holds moisture in the skin, and by doing so softens or soothes it. In psoriasis, these agents can be used to ease itching, reduce scaling, soften cracked areas and help the penetration of other topical treatments.

endotoxin: A substance found in the cell walls of certain bacteria that can be extremely toxic to people, producing fever, shock, and even death.

epidermis: The outer layers of the skin consisting of an outer, dead layer and a deeper, living, cellular zone. Unlike the dermis, the epidermis does not contain nerve endings or blood vessels.

eruptions: Lesions on the skin that are usually red, raised, and easily visible.

erythema: Redness of the skin, which is often a sign of infection or inflammation and may be caused by sunburn.

erythrodermic psoriasis: This is also sometimes called exfoliative psoriasis. It is the least common type of psoriasis, in which a large area of the skin is bright red and inflamed. This may cause difficulty regulating the body's temperature and heart rate.

exfoliative psoriasis: See erythrodermic psoriasis.


flexural psoriasis: (Also known as inverse psoriasis). Psoriasis characterised by bright red, smooth patches found in the folds of the skin. This type of psoriasis is found primarily in areas such as the armpits, under the breasts, and in other skin-folds around the genitals and buttocks.


gene: A specific sequence of DNA that determines a particular characteristic (such as eye color) and is found at a given location on a chromosome.

Goeckerman regimen: A treatment for mild psoriasis consisting of crude coal tar together with UVB phototherapy, usually administered in a hospital or a psoriasis clinic.

gold: This precious metal can be used in drug form: either oral or injectable. It is sometimes used in the treatment of psoriatic arthritis. Careful monitoring is required.

guttate psoriasis: The second most common form of psoriasis, characterised by small, pink or red drops on the skin. This type of psoriasis may cover a large portion of the body and is usually found on the chest, back, arms, or legs. Symptoms may be triggered by viral respiratory infections or certain bacterial (streptococcal) infections. Some cases go away without treatment in a few weeks, while many cases are more persistent and require treatment.


hand/foot therapy: A treatment for psoriasis that uses specialised ultraviolet light units on the palms of the hands and soles of the feet.

hepatic fibrosis: the formation of hard, fibrotic tissue in the liver leading to loss of function and liver failure. Long term treatment of psorisis with methotrexate can raise the risk of hepatic fibrosis.

human monoclonal antibody: A monoclonal antibody composed entirely of human derived amino acids.

humanised monoclonal antibody: A monoclonal antibody comprising the CDR of a murine antibody and the variable and constant regions of a human antibody.

hydroxyurea: One of the older anti-cancer drugs that is sometimes used in the treatment of psoriasis. When combined with acitretin, it can become more effective. Either in combination or alone, its use requires careful blood monitoring.

hypercalcaemia: An abnormal rise in the amount of calcium in the blood. This can occur as a side effect of overuse of calcipotriene.

hybridoma: a hybrid cell made in the laboratory by fusing a B lymphocyte that produces an antibody with a cancer cell, in order to allow the continued production of a specific antibody. Biological drugs for psoriasis that contain antibodies may be manufactured in this way.


IL-2 fusion toxins: Toxins that selectively bind to activated T cells and destroy them.

immune-mediated disorder: A disorder in which the normal function of the immune system is damaged, so that the body launches an immune response against its own tissue.

immunomodulator: A substance that alters the body's immune response.

immune response: The reactions of the immune system to foreign substances.

immune system: The body's mechanism for protecting against infections and diseases. It includes the cells that recognise and neutralise foreign substances.

inverse psoriasis: This is also known as flexural psoriasis. It is psoriasis that occurs in the skin folds, such as the underarm or groin area and can cause significant discomfort when one part of the skin rubs against another.

inflammation: Localised redness, swelling, and pain in response to infection or injury.

interferons: Proteins formed when cells are exposed to a virus or another particle of nucleic acid. Interferons can be used therapeutically for certain diseases such as psoriasis.

intergluteal: Between the buttocks.

intertriginous areas: These are areas where skin comes into contact with itself, such as the armpits, in the groin and beneath breasts. These areas can be more prone to types of infection, because they are hot and often sweaty. Side effects of steroids can be made worse in these areas due to the steroids being held in contact with the skin for longer periods of time.

interleukins: A group of cytokines produced mainly by T cells that direct other cells to divide and proliferate.


keratin: Any of a family of proteins that form the primary chemical components of the skin, hair, and nails.

keratinocytes: The cells in the epidermis that manufacture the fibrous protein keratin.

keratolysis: A disease in which the outer layer of skin is shed on a regular basis.

keratolytic: A substance that promotes the softening and peeling of the epidermis.

Koebner's phenomenon: Psoriasis that develops at an injury site.


Langerhans cells: These are dendritic cells which are specific to the skin.

lesion: An abnormal change, usually well defined, in the structure of an organ or part of the body; caused by injury or disease.

leukocytes: Any of the various white blood cells, which together make up the immune system. Neutrophils, lymphocytes and monocytes are all leukocytes.

lymphocytes: A type of leukocyte found in the blood, lymph nodes and certain organs. Lymphocytes are continuously made in the bone marrow (see also B lymphocytes and T lymphocytes).


maintenance program: A treatment program that is initiated to keep a disease in remission after an intensive course of therapy.

malignant melanoma: A potentially fatal form of skin cancer. Psoriasis patients receiving PUVA should be carefully screened for this, even after they have finished their therapy; usually treatable when detected early.

mild psoriasis: A condition in which only a few areas of the body have lesions from psoriasis.

memory cell: A cell in the immune system that, when exposed to an invading pathogen, replicates itself and remains in the lymph nodes searching for the same antigen, resulting in a more efficient and rapid response to any subsequent attack.

methotrexate: A medication that slows the production of skin cells by suppressing the immune system. Doctors may prescribe it for severe psoriasis, especially serious cases of pustular or erythrodermic psoriasis, and for psoriatic arthritis.

moderate psoriasis: Psoriasis that covers 3% to 10% of the body.

monoclonal antibody: An antibody that is made in large amounts in a laboratory and may be used to treat certain diseases.

murine monoclonal antibody: A monoclonal antibody composed entirely of murine derived amino acids.

multifactorial: Resulting from multiple factors interacting together.


nail psoriasis: Psoriasis that affects the fingernails and toenails and involves any of a number of changes to the nail area, including discolouration and the formation of small pits in the nails.

narrow-band UVB light therapy: Ultraviolet light in a narrow band of 311 nm to 313 nm, thought to be faster acting, and possibly safer than other UV light treatments.


oedema: A buildup of fluid in cells or tissues that produces swelling, often in the lower legs and feet.

Oral medication: Medication taken by mouth.

Over-the-counter (OTC): Nonprescription medication.


palmar plantar psoriasis: A form of psoriasis that is characterised by pustules on the palms and soles of the feet.

PASI score: Psoriasis Area Severity Index score, a number representing the size, redness, thickness, and scaliness of a person's psoriasis.

photochemotherapy: The addition of drugs to light therapy in order to intensify its effects.

photosensitivity: Increased sensitivity to the sun's light or other UV sources.

phototherapy: A common treatment for psoriasis using ultraviolet light.

plaque psoriasis: The most common form of psoriasis, also known as psoriasis vulgaris, recognised by red, raised lesions covered by silvery scales. About 80% of psoriasis patients have this type.

plaques: Patches of thickened and reddened skin covered by silvery scales.

plasminogen activator: A substance that plays a role in the accumulation of white blood cells that is found at high concentrations in psoriatic skin.

PSA: The Psoriasis Symptom Assessment (PSA) is a measure of the patient's frequency and severity of symptoms.

psoralen: A photosensitising drug used in combination with UVA to treat psoriasis (also known as PUVA therapy).

psoriasis: A chronic, non-contagious disease that occurs when the growth of new skin cells rapidly accelerates, resulting in thick, red, scaly, inflamed patches on the skin surface. There is currently no cure for psoriasis, but many treatment options are available.

psoriatic arthritis: A type of arthritis that is often characterised by pain, stiffness, and swelling around the joints; a decreased range of motion in the affected joints; nail changes such as pitting; and skin psoriasis. It develops in 10% to 30% of people with psoriasis, but it may also occur on its own.

psychological: Relating to the mind. Like many diseases, psoriasis may have psychological effects on a person's self-esteem and emotions in addition to physical effects.

psychosocial: Involving both the social and psychological aspects of a person's life. For example, psoriasis patients often report that the disease affects their self-confidence at work, at parties, or on dates.

pus: Thick, opaque, usually yellowish-white fluid made up of dead tissue, dead bacteria, and white blood cells.

pustular psoriasis: A type of psoriasis characterised by blisters of pus on the skin, usually on the palms or soles of the feet. The pustules are not infectious.

pustule: A small, circumscribed elevation of the skin containing pus.

PUVA: psoralen plus ultraviolet A is a treatment that combines exposure to ultraviolet A (UVA) light with a medicine called psoralen. Psoralen is believed to heighten photosensitivity and increase the skin's response to UVA for people with moderate to severe psoriasis.


rebound: A severe and sudden change that occurs in psoriasis when systemic therapy is suddenly halted. This change leaves the patient's psoriasis in a significantly worse condition than before the treatment was started. Rebound may also include a change in the nature of the psoriasis, for example, from plaque to pustular form. In some cases, rebound may be recognized early as new onset, severe and extensive erythema.

receptor: A structure on the surface of a cell that specifically recognises and binds to a particular substance. The binding of a substance to its receptor often signals a change in the activity of the cell. Many medications are effective because they are recognised by specific receptors in the body.

remission: The lessening of the symptoms of a disease, or a period of time during which the symptoms of a disease are decreased. Remission does not indicate that a disease is cured.

retinoids: Vitamin A derivatives often used in topical or oral psoriasis therapy.

rheumatoid arthritis: A chronic autoimmune disease characterised by pain, stiffness, inflammation, swelling, and, sometimes, destruction of joints.

rheumatologist: A specialist in the treatment of arthritis and related diseases.

rotational therapy: A strategy in which a doctor rotates a patient's treatments periodically, from one to another, to reduce toxicity and to allow for longer periods of benefit from each agent.


salicylic acid: A chemical that helps remove scales, which allows topical medications to penetrate the skin more successfully.

scale: A silvery-white buildup of dead skin cells that covers plaques in the most common form of psoriasis. These scales come loose from the plaque and are shed.

scalp psoriasis: Plaque psoriasis that appears on the scalp. It is often itchy and most visible around the ears and hairline. The constant flaking and shedding of dead skin cells give the appearance of severe dandruff.

severe psoriasis: Psoriasis that covers more than 10% of the skin's surface. The severity of psoriasis is also measured by the impact of the disease on a person's quality of life.

skin biopsy: Taking a small piece of skin to be examined under a microscope. This procedure is usually performed with the aid of a local anesthetic, and helps a dermatologist diagnose the type of skin disorder a patient has.

skin thinning: A condition in which the skin atrophies due to any variety of causes, including overuse of topical steroids.

squamous cell carcinoma: A form of skin cancer that is more aggressive than basal cell carcinoma. People who have received PUVA may be at risk of this type of skin cancer.

steroids: A synthetic hormone similar to that produced naturally by the adrenal glands that is available in pill, topical cream, and injectable forms.

Streptococcal sore throat: A type of bacterial infection of the throat that, in susceptible individuals, may trigger the onset of psoriasis, usually in a form called guttate psoriasis.

systemic: Affecting the entire body internally.

systemic treatment: A treatment, such as a pill or an injection.


T lymphocyte: A specific type of white blood cell that starts an immune response or actively works to attack and destroy foreign substances (antigens). Psoriasis is often considered a "T-cell-mediated" disease because T cells appear to be over-activated.

tacrolimus: An immune suppressant similar to cyclosporine.

tars: Natural, sticky substances used to treat psoriasis as in coal tar shampoos, topical creams, and ointments.

tazarotene: Vitamin A topical medication for the treatment of psoriasis.

topical: Describes medications that are applied directly to the surface of the skin. Topical treatments for psoriasis - including corticosteroids, salicylic acid, and coal tar - are most often used to treat mild forms of the disease.

tumour necrosis factor (TNF): One of the cytokines, or messengers, known to be fundamental to the disease process that underlies psoriasis. It often plays a key role in the onset and the continuation of skin inflammation.


Ultraviolet (UV) light: The type of light that emanates directly from the sun. It is classified into three categories according to wavelength: UVC, UVB, and UVA. Ultraviolet light can also be simulated using light panels and light boxes. This is a popular treatment for psoriasis.

UVB phototherapy: Treatment involving measured doses of UV light in the UVB wavelength. Two types are broadband UVB, and the less common narrow-band UVB. Indicated for moderate to severe psoriasis, UVB treatment can reduce the abnormal growth of skin cells and can lessen inflammation.


vitamin A: Derivatives of this vitamin, called retinoids, are used in its oral and topical forms to treat psoriasis.

vitamin D3: A topical vitamin used to treat psoriasis.

Copyright IFPA, International Federation of Psoriasis Associations