Psoriasis is a common and chronic skin condition in which new skin cells are produced more rapidly than normal and do not shed as quickly, therefore causing dead skin cells to accumulate on the surface of the skin. This accumulation of skin cells causes the formation of dry, itchy, red patches or thick, scaling plaques that can be painful. Although psoriasis is a chronic (long-lasting) disease, you may experience times when your psoriasis symptoms worsen or improve, depending on various factors such as cold weather, smoking, infection, or a high level of stress. Psoriasis can also lead to the development of psoriatic arthritis in about 10-30% of patients. Symptoms of psoriatic arthritis include pain, stiffness, and swelling of the joints. There are different types of psoriasis that are named based on the types of lesions appearing on the skin surface. A few types include: plaque psoriasis, guttate psoriasis, and pustular psoriasis. Plaque psoriasis is the most common type and appears on the skin as dry, raised, red patches with silvery scales. Guttate psoriasis is usually triggered by a bacterial infection such as strep throat and appears as small, drop-shaped lesions on the scalp, trunk, arms, and legs. Pustular psoriasis is a more uncommon type and appears on the skin as pus-filled or blister-like lesions. This type of psoriasis can occur all over the body or be found in small areas on the hands and feet.