Surface scales come off easily and are shed constantly, but those below the surface of the skin are quite adherent. When forcibly removed, they may leave tiny bleeding points known as the Auspitzs sign. The plaques may cover large areas of skin and merge into each other. Often, the lesions appear in the same place on the right and left sides of the body. Any body surface can be affected, but the lesions appear most often on the scalp, knees, and elbows.
Lesions vary in size and in shape from individual to individual.
Sometimes the nails are affected, causing pitting and scaling of the base, or ridging and furrowing with an alteration in the transparency of the nail. Emotional response to the persistence and cosmetically disfiguring effects of psoriasis can be severe. To date, no other disease, with the exception of psoriatic arthritis, has been associated with psoriasis. Psoriasis, however, can appear simultaneously with any other disease. Statistically, about 10 percent of people with psoriasis develop a kind of arthritis known as psoriatic arthritis.