Psoriasis (pronounced //; from Greek , meaning "itching condition" or "being itchy",[1]psora "itch" + -sis "action, condition"; also termed psoriasis vulgaris),[2] is a common, chronic immune-mediated skin disease which may also affect the joints.[2]

Psoriasis is characterized by scaly, erythematous (reddened) patches, papules, and plaques which are usually pruritic (itchy).[2] There are five main types of psoriasis: plaque, guttate, inverse, pustular, and erythrodermic.[3] The most common form, plaque psoriasis, is commonly seen as red and white hues of scaly patches appearing on the top first layer of the epidermis (skin). Some patients, though, have no dermatological signs or symptoms.[medical citation needed] In plaque psoriasis, skin rapidly accumulates at these sites, which gives it a silvery-white appearance. Plaques frequently occur on the skin of the elbows and knees, but can affect any area, including the scalp, palms of hands and soles of feet, and genitals. In contrast to eczema, psoriasis is more likely to be found on the outer side of the joint. Fingernails and toenails are frequently affected (psoriatic nail dystrophy) and can be seen as an isolated sign. Psoriasis can also cause inflammation of the joints, which is known as psoriatic arthritis. Up to 30% of individuals with psoriasis also have psoriatic arthritis.[4]

The causes of psoriasis are not fully understood. It is generally considered a genetic disease which can be triggered or influenced by environmental factors.[2] Local psoriatic changes can be triggered by an injury to the skin known as the Koebner phenomenon.[5] Various environmental factors have been suggested as aggravating to psoriasis, including oxidative stress,[6]stress, withdrawal of systemic corticosteroid, as well as other environmental factors, but few have shown statistical significance.[7] Psoriasis occurs when the immune system mistakes a normal skin cell for a pathogen, and sends out faulty signals that cause overproduction of new skin cells. It is not contagious.[8]

There is no cure,[8] but various treatments can help to control the symptoms.[9][10] There are many treatments available, but because of its chronic recurrent nature, psoriasis is a challenge to treat. Withdrawal of corticosteroids (topical steroid cream) can aggravate the condition due to the 'rebound effect' of corticosteroids.[11]

The disorder is a chronic, recurring condition that varies in severity from minor localized patches to complete body coverage. It occurs in 1-3% of the general population.[8]

Psoriasis is classified as a papulosquamous disorder.[4] It is most commonly classified according to historical morphologic descriptions.[2] Variants include plaque, pustular, guttate, and flexural psoriasis. This section describes each type (with ICD-10 code).[12]

Another classification takes into account genetic and demographic factors. Type 1 has a positive family history, starts before the age of 40 and is associated with the human leukocyte antigen, HLA-Cw6. Conversely, Type 2 does not show a family history, presents before age 40 and is not associated with HLA-Cw6.[13] Type 1 accounts for about 75% of persons with psoriasis.[14]

Psoriasis can also be classified into nonpustular and pustular types as follows.[15]

Pustular psoriasis (L40.13, L40.82) appears as raised bumps that are filled with noninfectious pus (pustules).[17] The skin under and surrounding the pustules is red and tender. Pustular psoriasis can be localised, commonly to the hands and feet (palmoplantar pustulosis), or generalised with widespread patches occurring randomly on any part of the body. Types include:

Additional types of psoriasis include:[18]

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Psoriasis - Wikipedia, the free encyclopedia