Psoriasis: A common genetically determined, chronic, inflammatory skin disease characterized by rounded erythematous, dry, scaling patches. The lesions have a predilection for nails, scalp, genitalia, extensor surfaces, and the lumbosacral region. Accelerated epidermopoiesis is considered to be the fundamental pathologic feature in psoriasis.Dermatologic Agents: Drugs used to treat or prevent skin disorders or for the routine care of skin.Arthritis, Psoriatic: A type of inflammatory arthritis associated with PSORIASIS, often involving the axial joints and the peripheral terminal interphalangeal joints. It is characterized by the presence of HLA-B27-associated SPONDYLARTHROPATHY, and the absence of rheumatoid factor.PUVA Therapy: Photochemotherapy using PSORALENS as the photosensitizing agent and ultraviolet light type A (UVA).Ultraviolet Therapy: The use of ultraviolet electromagnetic radiation in the treatment of disease, usually of the skin. This is the part of the sun's spectrum that causes sunburn and tanning. Ultraviolet A, used in PUVA, is closer to visible light and less damaging than Ultraviolet B, which is ionizing.Coal Tar: A by-product of the destructive distillation of coal used as a topical antieczematic. It is an antipruritic and keratoplastic agent used also in the treatment of psoriasis and other skin conditions. Occupational exposure to soots, tars, and certain mineral oils is known to be carcinogenic according to the Fourth Annual Report on Carcinogens (NTP 85-002, 1985) (Merck Index, 11th ed).HLA-C Antigens: Class I human histocompatibility (HLA) antigens encoded by a small cluster of structural genes at the C locus on chromosome 6. They have significantly lower immunogenicity than the HLA-A and -B determinants and are therefore of minor importance in donor/recipient crossmatching. Their primary role is their high-risk association with certain disease manifestations (e.g., spondylarthritis, psoriasis, multiple myeloma).Acitretin: An oral retinoid effective in the treatment of psoriasis. It is the major metabolite of ETRETINATE with the advantage of a much shorter half-life when compared with etretinate.Skin: The outer covering of the body that protects it from the environment. It is composed of the DERMIS and the EPIDERMIS.Anthralin: An anthracene derivative that disrupts MITOCHONDRIA function and structure and is used for the treatment of DERMATOSES, especially PSORIASIS. It may cause FOLLICULITIS.Keratolytic Agents: Agents that soften, separate, and cause desquamation of the cornified epithelium or horny layer of skin. They are used to expose mycelia of infecting fungi or to treat corns, warts, and certain other skin diseases.Keratinocytes: Epidermal cells which synthesize keratin and undergo characteristic changes as they move upward from the basal layers of the epidermis to the cornified (horny) layer of the skin. Successive stages of differentiation of the keratinocytes forming the epidermal layers are basal cell, spinous or prickle cell, and the granular cell.Nail Diseases: Diseases of the nail plate and tissues surrounding it. The concept is limited to primates.Clobetasol: A derivative of PREDNISOLONE with high glucocorticoid activity and low mineralocorticoid activity. Absorbed through the skin faster than FLUOCINONIDE, it is used topically in treatment of PSORIASIS but may cause marked adrenocortical suppression.Dermatology: A medical specialty concerned with the skin, its structure, functions, diseases, and treatment.Epidermis: The external, nonvascular layer of the skin. It is made up, from within outward, of five layers of EPITHELIUM: (1) basal layer (stratum basale epidermidis); (2) spinous layer (stratum spinosum epidermidis); (3) granular layer (stratum granulosum epidermidis); (4) clear layer (stratum lucidum epidermidis); and (5) horny layer (stratum corneum epidermidis).Phototherapy: Treatment of disease by exposure to light, especially by variously concentrated light rays or specific wavelengths.Severity of Illness Index: Levels within a diagnostic group which are established by various measurement criteria applied to the seriousness of a patient's disorder.Scalp DermatosesInterleukin-23: A heterodimeric cytokine that plays a role in innate and adaptive immune responses. Interleukin-23 is comprised of a unique 19 kDa subunit and 40 kDa subunit that is shared with INTERLEUKIN-12. It is produced by DENDRITIC CELLS; MACROPHAGES and a variety of other immune cellsDermatitis, Atopic: A chronic inflammatory genetically determined disease of the skin marked by increased ability to form reagin (IgE), with increased susceptibility to allergic rhinitis and asthma, and hereditary disposition to a lowered threshold for pruritus. It is manifested by lichenification, excoriation, and crusting, mainly on the flexural surfaces of the elbow and knee. In infants it is known as infantile eczema.Skin DiseasesAdministration, Topical: The application of drug preparations to the surfaces of the body, especially the skin (ADMINISTRATION, CUTANEOUS) or mucous membranes. This method of treatment is used to avoid systemic side effects when high doses are required at a localized area or as an alternative systemic administration route, to avoid hepatic processing for example.Skin Diseases, Vesiculobullous: Skin diseases characterized by local or general distributions of blisters. They are classified according to the site and mode of blister formation. Lesions can appear spontaneously or be precipitated by infection, trauma, or sunlight. Etiologies include immunologic and genetic factors. (From Scientific American Medicine, 1990)Rare Diseases: A large group of diseases which are characterized by a low prevalence in the population. They frequently are associated with problems in diagnosis and treatment.Cytophotometry: A method for the study of certain organic compounds within cells, in situ, by measuring the light intensities of the selectively stained areas of cytoplasm. The compounds studied and their locations in the cells are made to fluoresce and are observed under a microscope.Calcium: A basic element found in nearly all organized tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.Inflammation: A pathological process characterized by injury or destruction of tissues caused by a variety of cytologic and chemical reactions. It is usually manifested by typical signs of pain, heat, redness, swelling, and loss of function.Calcium Signaling: Signal transduction mechanisms whereby calcium mobilization (from outside the cell or from intracellular storage pools) to the cytoplasm is triggered by external stimuli. Calcium signals are often seen to propagate as waves, oscillations, spikes, sparks, or puffs. The calcium acts as an intracellular messenger by activating calcium-responsive proteins.Biology: One of the BIOLOGICAL SCIENCE DISCIPLINES concerned with the origin, structure, development, growth, function, genetics, and reproduction of animals, plants, and microorganisms.Pyrophosphatases: A group of enzymes within the class EC 3.6.1.- that catalyze the hydrolysis of diphosphate bonds, chiefly in nucleoside di- and triphosphates. They may liberate either a mono- or diphosphate. EC 3.6.1.-.Healthy People Programs: Healthy People Programs are a set of health objectives to be used by governments, communities, professional organizations, and others to help develop programs to improve health. It builds on initiatives pursued over the past two decades beginning with the 1979 Surgeon General's Report, Healthy People, Healthy People 2000: National Health Promotion and Disease Prevention Objectives, and Healthy People 2010. These established national health objectives and served as the basis for the development of state and community plans. These are administered by the Office of Disease Prevention and Health Promotion (ODPHP). Similar programs are conducted by other national governments.Encyclopedias as Topic: Works containing information articles on subjects in every field of knowledge, usually arranged in alphabetical order, or a similar work limited to a special field or subject. (From The ALA Glossary of Library and Information Science, 1983)MedlinePlus: NATIONAL LIBRARY OF MEDICINE service for health professionals and consumers. It links extensive information from the National Institutes of Health and other reviewed sources of information on specific diseases and conditions.Gross Domestic Product: Value of all final goods and services produced in a country in one year.Environment: The external elements and conditions which surround, influence, and affect the life and development of an organism or population.Autoimmunity: Process whereby the immune system reacts against the body's own tissues. Autoimmunity may produce or be caused by AUTOIMMUNE DISEASES.Autoimmune Diseases: Disorders that are characterized by the production of antibodies that react with host tissues or immune effector cells that are autoreactive to endogenous peptides.Phenotype: The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.Dermatitis: Any inflammation of the skin.Rosacea: A cutaneous disorder primarily of convexities of the central part of the FACE, such as FOREHEAD; CHEEK; NOSE; and CHIN. It is characterized by FLUSHING; ERYTHEMA; EDEMA; RHINOPHYMA; papules; and ocular symptoms. It may occur at any age but typically after age 30. There are various subtypes of rosacea: erythematotelangiectatic, papulopustular, phymatous, and ocular (National Rosacea Society's Expert Committee on the Classification and Staging of Rosacea, J Am Acad Dermatol 2002; 46:584-7).Cellular Phone: Analog or digital communications device in which the user has a wireless connection from a telephone to a nearby transmitter. It is termed cellular because the service area is divided into multiple "cells." As the user moves from one cell area to another, the call is transferred to the local transmitter.Computers, Handheld: A type of MICROCOMPUTER, sometimes called a personal digital assistant, that is very small and portable and fitting in a hand. They are convenient to use in clinical and other field situations for quick data management. They usually require docking with MICROCOMPUTERS for updates.Word Processing: Text editing and storage functions using computer software.ArthritisArthritis, Rheumatoid: A chronic systemic disease, primarily of the joints, marked by inflammatory changes in the synovial membranes and articular structures, widespread fibrinoid degeneration of the collagen fibers in mesenchymal tissues, and by atrophy and rarefaction of bony structures. Etiology is unknown, but autoimmune mechanisms have been implicated.Practice Guidelines as Topic: Directions or principles presenting current or future rules of policy for assisting health care practitioners in patient care decisions regarding diagnosis, therapy, or related clinical circumstances. The guidelines may be developed by government agencies at any level, institutions, professional societies, governing boards, or by the convening of expert panels. The guidelines form a basis for the evaluation of all aspects of health care and delivery.Therapeutic Misconception: Misunderstanding among individuals, frequently research subjects, of scientific methods such as randomization and placebo controls.Mythology: A body of stories, the origins of which may be unknown or forgotten, that serve to explain practices, beliefs, institutions or natural phenomena. Mythology includes legends and folk tales. It may refer to classical mythology or to a body of modern thought and modern life. (From Webster's 1st ed)Physiology: The biological science concerned with the life-supporting properties, functions, and processes of living organisms or their parts.Health Knowledge, Attitudes, Practice: Knowledge, attitudes, and associated behaviors which pertain to health-related topics such as PATHOLOGIC PROCESSES or diseases, their prevention, and treatment. This term refers to non-health workers and health workers (HEALTH PERSONNEL).Social Stigma: A perceived attribute that is deeply discrediting and is considered to be a violation of social norms.Helping Behavior: Behaviors associated with the giving of assistance or aid to individuals.