In 30 to 40 percent of patients having Vitiligo, there is a history of this disease in the family, because of genetic transmission (by autosomal dominant gene). Though Vitiligo may appear at any age, in about 50% of the patients, this disease can be detected before the age of 20 years. To begin with it starts with the unexposed parts of the body and later it affects those parts of the body (e.g. face, back of the hand), which are exposed to the sun. White patches may also appear due to various other reasons such as radiation therapy, after mental tension, intake of certain medicines (like Chloroquin in Malaria), contact with chemical substances like Phenol, nutritional deficiencies like B12 or due to certain diseases like scabies, or psoriasis. Vitiligo is often seen on the skin which is susceptible to continuous friction or blows (elbow, knee and ankle). Generally, the distribution of patches is equal on both, the left as well as the right, sides of the body. The edges of these patches are darker.