Leucism

Not to be confused with Albinism.

Leucistic white lions owe their colouring to a recessive allele. Note the eyes and lips remain the normal colour. Studies have shown that the reduced pigment comes from a mutation in the gene for tyrosinase, the same as causes Type I oculocutaneous albinism in humans.

This white horse owes its coloring to a dominant allele (dominant white).

A leucistic rock dove. Both the eyes and legs are still of the normal colour.

Leucism (/ˈluːsɪzəm, -kɪz-/) or leukism, is a wide variety of conditions that result in partial loss of pigmentation in an animal—causing white, pale, or patchy coloration of the skin, hair, feathers, scales, or cuticles, but not the eyes. Some genetic conditions that result in a "leucistic" appearance include piebaldism, Waardenburg syndrome, vitiligo, Chédiak–Higashi syndrome, flavism, isabellinism, xanthochromism, axanthism, amelanism, and melanophilin mutations. Pale patches of skin, feathers, or fur (often referred to as "depigmentation") can also result from injury.