Leucism is a condition caused by the expression of a recessive gene. The genes primarily responsible for leucism are the c-kit gene and the mitf gene. During the embryonic state, these genes produce a defective transmembrane protein which results in a lack of melanocytes or cells capable of making pigment. As a result, the animal exhibits white coat color or patches over the body.
Generally, leucistic animals retain some part of their normal pigmentation, and partial expression of leucism can be exhibited in the form of an animal having spotted or piebald appearance. The skin appears pink, its coat or fur color may vary from blond to beige to pure white.
In the animal world though, leucism tends to be disadvantageous, since the animal loses the advantage of camouflage that markings on the skin or colored coat present. Leucism is often confused with albinism, but there are significant differences between the two.