Vitiligo is characterized by depigmentation in large or small areas of the skin. There is a complete lack of melanin production in the hypopigmented areas, due to the destruction of previously active melanocytes. This is in contrast to albinism, in which melanocytes are present but there is little or no pigmentation because of defective or absent tyrosinase. Although the etiology of vitiligo remains unknown, an autoimmune theory is gaining acceptance.