soriasis (pronounced /s?'ra??s?s/) is a chronic, non-infectious disease that affects mainly the skin. It is currently suspected to be autoimmune in origin. It commonly causes red, scaly patches to appear on the skin, although some patients have no dermatological symptoms. The scaly patches caused by psoriasis, called psoriatic plaques, are areas of inflammation and excessive skin production. Skin rapidly accumulates at these sites and takes on 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 extensor aspect of the joint.

The disorder is a chronic recurring condition that varies in severity from minor localized patches to complete body coverage. Fingernails and toenails are frequently affected (psoriatic nail dystrophy) and can be seen as an isolated symptom. Psoriasis can also cause inflammation of the joints, which is known as psoriatic arthritis. Ten to fifteen percent of people with psoriasis have psoriatic arthritis.,

The cause of psoriasis is not exact, but it is believed to have a genetic component and it can be triggered by a prolonged injury to the skin known as Koebener phenomena[citation needed]. Various environmental factors have been suggested as aggravating to psoriasis including stress, withdrawal of systemic corticosteroid, excessive alcohol consumption, and smoking but few have shown statistical signifcance. There are many treatments available, but because of its chronic recurrent nature psoriasis is a challenge to treat.