Vitiligo is a disease in which the pigment cells of the skin, melanocytes, are destroyed in certain areas. Vitiligo results in 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. Vitiligo is a condition in which white patches develop on the skin. Any location on the body can be affected and most people with vitiligo have white patches on many areas of the body. Causes of Vitiligo. Melanin is the pigment that gives the skin its characteristic color. Much more complicated is the use of topical Oxsoralen (8-MOP). Oxsoralen is highly phototoxic (likely to cause a sunburn), and the phototoxicity lasts for 3 days or more. This should be performed only as an office procedure, only for small spots, and only by experienced physicians on well-informed patients. As with oral psoralens, 15 or more treatments may be required to initiate a response, and 100 or more to finish.