Vitiligo is a disease in which the pigment cells of the skin, skin fading, melanocytes, are destroyed in certain areas. Symptoms and signs of vitiligo include loss of skin color in the form of depigmented, or white, patches of skin in any location on the body. Vitiligo can be focal and localized to one area, or it may affect several different areas on the body. The exact cause of vitiligo is unknown, although most experts believe that it is an autoimmune condition in which the body's immune system mistakenly attacks and destroys certain cells within the body. Most people who have vitiligo will develop the condition prior to age 40; about half develop it before age 20. Vitiligo may have a genetic component, as the condition tends to run in families. Vitiligo is sometimes associated with other medical conditions, including thyroid dysfunction. There is no way to determine if vitiligo will spread or remain confined to one location. Vitiligo is not painful and does not have significant health consequences; however, it can have emotional and psychological consequences.