Psoriasis is a chronic, relapsing skin disease, characterized by the presence on the skin of scaly patches that may flake, and which disappear leaving no trace.

Psoriasis is a noncommunicable and benign disease, which tends to spontaneously enter remission and relapse. A characteristic symptom of the disease is the appearance of reddish or pinkish raised flat lumps with distinct edges. These papules vary in size and are covered in silver or silver-grey plaques. Lesions often have a tendency to merge together. The patches appear most frequently on the skin of the limbs (mainly on the elbows and knees), on the small of the back, around the buttocks, on the scalp, and on the skin of the feet and hands. Psoriasis can also occur on the nails, where it is characterized by soiling, thickening, staining, fragility, and a yellow tint. Recent reports connect psoriasis with metabolic disturbances (such as high levels of cholesterol) and with increased chances of circulatory diseases. Some patients with psoriasis may experience joint problems, including pain and swelling. Psoriatic arthritis, apart from causing skin lesions, involves chronic swelling of the joints. The types of psoriasis treatment are local therapy, general therapy, and phototherapy. The first stage of treatment is cleaning the lesion of the plaques, using local preparations containing urea, salicylic acid, and sulphur. Next comes the so-called reduction stage, in which the cells of the epidermis are prevented from dividing excessively, which is what causes the psoriatic lesions. To this end, local preparations of tar, dithranol (anthralin), local corticosteroids (which must not be used continuously), analogues of vitamin D, and local retinoids are administered. Phototherapy is an effective method: it involves exposing the plaques to ultraviolet rays emitted by a special lamp. This method is easy to apply and useful where large areas of skin are affected. The UV exposure can be combined with the use of psoralen and retinoids. In severe cases, or when the condition does not respond to local treatment or phototherapy, it may be necessary to employ general treatments, employing orally administered immunomodulating medicines, such as ciclosporin, methotrexate, or oral retinoids. In severe and stubborn cases, there is also the possibility of incorporating so-called biological treatment (monoclonal antibodies). The correct and systematic treatment of psoriasis, accompanied with the appropriate care of the skin, can give most patients relief from the lesions.