Leucism is a wide variety of conditions that result in the 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. Wikipedia

Lack of pigment cells in an animal, in part or full Wikidata

An animal condition in which there is partial loss of pigmentation resulting in white, pale, or patchy coloration of the skin, hair, feathers, scales or cuticle, but not the eyes (caused by a reduction in multiple types of pigment, not just melanin). Wiktionary

Partial loss of pigmentation. Wiktionary (translation)