leucism

thumb|right|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.]] thumb|right|alt=All-white dominant white horse with pink skin, brown eyes, and white hooves.|This white (horse)|white horse owes its coloring to a dominant allele ([[dominant white).]] thumb|A leucistic rock dove. Both the eyes and legs are still of the normal colour. Leucism () 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.

== Details == thumb|thumbtime=1|(video) A white tiger at Tobu Zoo, in Saitama, [[Japan. This phenotype is due to a mutation in the same gene that results in Type IV oculocutaneous albinism in humans.]] Leucism is often used to describe the phenotype that results from defects in pigment cell differentiation and/or migration from the neural crest to skin, hair, or feathers during development. This results in either the entire surface (if all pigment cells fail to develop) or patches of body surface (if only a subset are defective) lacking cells that can make pigment.