Alefacept: A biologic drug that is given by injection and is FDA approved for treating adults who have moderate to severe chronic plaque psoriasis.

Anthralin: A topical agent prescribed for the treatment of psoriasis.

Antibody: A Y-shaped protein that is secreted into the blood or lymph to fight against bacteria, viruses and other foreign particles.

Chronic: Long-lasting, ongoing.

Clinical trial: investigational studies of new treatments, new uses of existing treatment, or new screening methods to detect disease.

Coal tar bath: Topical coal tar preparations are used to treat the scaling, inflammation and itching of psoriasis and other skin disorders. The coal tar solution is added to bath water for greater coverage and penetration.  

Costimulatory signal: In interactions between cells of the immune system, a costimulatory "second messenger" molecule is sometimes needed to complete the cell-to-cell transmission of a signal that initiates an immune response to infection or injury.

Cyclosporine: A prescription drug that decreases the body's abnormal immune response.

Cytokine: Cytokines are a large group of molecules that regulate interactions in the immune system. Cytokines are messengers that carry biochemical signals to regulate local and systemic immune responses, inflammatory reactions, wound healing, formation of blood cells, and many other biologic processes. More than 100 cytokines have been identified.

Erythrodermic psoriasis: Psoriasis characterized by severe redness and shedding of the body surface.

Exfoliation: Peeling and sloughing off of the skin's tissue cells.

Gene: The material that forms the biologic code for who we are. This code is passed on to our children.

Guttate psoriasis: Psoriasis characterized by red, drop-like dots on the skin.

Human leucocyte antigen (HLA): Immune system markers strongly associated with the causes(s) of psoriasis.

Immune system: The biochemical complex that protects the body against organisms (infections) and other foreign bodies that lead to illness.

Infection: The invasion of the body by microorganisms that reproduce and multiply, causing disease.

Informed consent: the process by which a volunteer for a clinical trial agrees to participate after being fully informed regarding purposes of the trial, risks and benefits associated with participation in the trial, and whether volunteers will be randomized to receive treatment or placebo.

Inverse psoriasis: Psoriasis characterized by smooth, inflamed lesions in body folds.

Koebner’s phenomenon: Psoriatic lesions appear at the site of injury, infection or other skin problem. The lesion may mark the initial onset of psoriasis, or may be a new lesion in an existing case of psoriasis. See trigger.

Lesions: A wound or injury to the skin.

Medical history: A collection of information obtained from the patient and from other sources concerning the patient's past and current health.

Methotrexate: An agent prescribed for the treatment of moderate to severe psoriasis.

Noncontagious: Incapable of being transmitted from person to person.

Oral: By the mouth.

Palmar-plantar psoriasis: Psoriasis characterized by pus-like blisters on the skin (usually hands or feet).  Also known as pustular psoriasis.

Pastes: Ointments in which powder is suspended.  Pastes are drying and less greasy than ointments.

Phototherapy: Treatment with artificial ultraviolet light.

Placebo: a pharmacologically inactive substance with no medicinal value, used as method for "control" in clinical trials.

Plaque: A flattish, raised patch on the skin.

Plaque psoriasis: Psoriasis characterized by red, silvery-white, scaly skin lesions (most common variety of psoriasis).

Predisposed: Susceptible, likely to get.

Psoriatic arthritis: A genetically driven autoimmune disease that occurs in less than 10% of persons with psoriasis. Large and small joints are affected. Psoriatic arthritis is often associated with psoriasis in fingernails and toenails.

Pustular psoriasis: Psoriasis characterized by pus-like blisters on the skin (usually hands or feet). Also known as palmo-plantar pustular psoriasis.

PUVA: The acronym for Psoralen + ultraviolet light A. PUVA is a type of phototherapy used in treatment of psoriasis. Treatment requires the patient to ingest, topically apply, or bathe in a medication called psoralen before being exposed to UVA rays.

Retinoids: Vitamin A derivatives used in the prevention and treatment of various skin problems.

Scales: Thin flakes on the skin surface.

Shake lotions: A combination of a powder and liquid that must be shaken before application.

Skin biopsy:  A portion of skin is removed for microscopic examination.

Steroid: An abbreviated word for corticosteroids, which are powerful drugs used to control inflammation and itching of the skin.

Systemic: Pertaining to the body as a whole. 

Topical: On the skin.

Trigger: A nongentic, environmental factor that acts together with genetic predisposition to cause onset or worsening of psoriasis. Injuries and infections are common triggers. See Koebner’s phenomenon.

Ultraviolet light: The part of sunlight that has a short wavelength and encompasses the wavelengths that treat psoriasis. This type of light can also cause sunburn.