It can appear suddenly or gradually. It may affect any age but most commonly begins between 15 to 35 years old. It occurs most frequently in Caucasians.
Psoriasis is characterized by frequent episodes of recurrences and remissions.
Psoriasis seems to be an inherited disorder, and it appears to be related to the immune or inflammatory response . It is most commonly seen on the trunk, elbows, knees, scalp, skin folds, or fingernails, but it may affect any or all parts of the skin. Normally, skin takes about a month for its new cells to move from the lower layers of skin up to the surface. In psoriasis, this process takes only a few days, resulting in build-up of dead skin cells and formation of thick scales . Psoriasis is not contagious.