Vitiligo (pron-en?v?t??la??o?) is a chronic (Chronic (medicine)) disorder that causes depigmentation in patches of skin. It occurs when the melanocytes, the cells responsible for skin pigmentation (Human skin color) which are derived from the neural crest, die or are unable to function. The precise pathogenesis, or cause, of vitiligo is complex and not yet fully understood. There is some evidence suggesting it is caused by a combination of autoimmune (Autoimmunity), genetic (Genetics), and environmental factors. It is also common in people with thyroid disorders. The population incidence worldwide is considered to be less than 1 percent. Non-segmental vitiligo has a greater prevalence than the disorders other form(s).