Axanthism is a condition common in reptiles and amphibians, in which xanthophore metabolism is affected rather than synthesis of melanin, resulting in reduction or absence of red and yellow pteridine pigments. Leucism differs from albinism in that the melanin is, at least, partially absent but the eyes retain their usual colour. Some leucistic animals are white or pale because of chromatophore (pigment cell) defects, and do not lack melanin. Melanism is the direct opposite of albinism. An unusually high level of melanin pigmentation (and sometimes absence of other types of pigment in species that have more than one) results in an appearance darker than non-melanistic specimens from the same gene pool. In plants
In plants, albinism is characterised by partial or complete loss of chlorophyll pigments and incomplete differentiation of chloroplast membranes. Albinism in plants interferes with photosynthesis, which can reduce survivability. Some plant variations may have white flowers or other parts. However, these plants are not totally devoid of chlorophyll. Terms associated with this phenomenon are "hypochromia" and "albiflora".Plants that are pale simply from being in the dark are termed etiolated. Albino redwoods are rare examples of an albino tree with white needles; despite its lack of chlorophyll it may grow to substantial size as a parasite, usually on the base of the (normal) redwood tree from which it first grew. Only about sixty examples of albino redwoods are known. Additionally, an even smaller number of "chimeric" redwood trees have both normal and white needles.
While they are clear and precise for humans and other mammals, this is because the majority of mammals have only one pigment, melanin. Many animals have pigments other than melanin, and some also have structural colours. Some definitions of albinism, whilst taking most taxa into account, ignore others. So, "a person or animal with very pale skin, white hair or fur, and pink eyes caused by a medical condition that they were born with" and "a person or animal with white skin and hair and pink eyes" do not include feathers, scales or cuticles of birds, fish and invertebrates, nor do they include plants. Some definitions are too broad to be of much use, e.g. "an animal or plant with a marked deficiency in pigmentation".Other definitions of albinism encompass most of the major animal taxa, but ignore the several other pigments that non-mammalian animals have and also structural colouration. For example, "Absence of the pigment melanin in the eyes, skin, hair, scales, or feathers." refers only to the pigment melanin. Because of the various uses of different terms applied to colouration, some authors have indicated that the colour of the eyes is the defining characteristic of albinism, e.g. "This leads to a good diagnostic feature with which to distinguish leucistic and albino individuals – the colour of the eye."