Melanin is a substance which colors or pigments the skin. Melanocytes are cells found in the skin and hair follicles that produce melanin. In several diseases, including vitliigo, melanocytes are depleted or destroyed, reducing and eventually eliminating the supply of melanin. In the absence of melanin, the skin appears white in color. Depletion of melanocytes can also cause hair to become white.
The first white patches often occur on the hands, feet, arms, face, or lips. Other common areas for patches to appear are armpits, the groin, the navel and genitals. About half of all people who have vitiligo begin to lose pigment before they are 20 years old. Vitiligo usually does spread over time, but the rate of spreading can vary from rapid progression, to taking place over many years.
Approximately 65 million people worldwide have vitiligo, including up to 2 million people in the United States.
Vitiligo affects people of all races and both sexes equally, but often the appearance is more obvious in people with dark skin. Light-skinned people may notice the contrast between patches of vitiligo and areas of suntanned skin in the summer. The amount of pigment that is lost varies from person to person.
Approximately 30% of vitiligo cases occur with a familial clustering of cases and onset typically occurs by the ages of 20 to 30, with only rare occurrances in infancy or old age.