Leucism () is a wide variety of conditions that result in partial loss of

pigmentation A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly insoluble and chemically unreactive in water or another medium; in contrast, dyes are colored substances which are soluble or go in ...

in an

animal Animals are multicellular, eukaryotic organisms in the Biology, biological Kingdom (biology), kingdom Animalia (). With few exceptions, animals heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, ...

—causing white, pale, or patchy coloration of the skin, hair, feathers, scales, or cuticles, but not the eyes. It is occasionally spelled ''leukism''. Some genetic conditions that result in a "leucistic" appearance include piebaldism,

Waardenburg syndrome Waardenburg syndrome is a group of rare genetic conditions characterised by at least some degree of congenital hearing loss and pigmentation deficiencies, which can include bright blue eyes (or Heterochromia iridum, one blue eye and one brown ey ...

vitiligo Vitiligo (, ) is a chronic autoimmune disorder that causes patches of skin to lose pigment or color. The cause of vitiligo is unknown, but it may be related to immune system changes, genetic factors, stress, or sun exposure, and susceptibili ...

Chédiak–Higashi syndrome Chédiak–Higashi syndrome (CHS) is a rare autosomal recessive disorder that arises from a mutation of a lysosomal trafficking regulator protein, which leads to a decrease in phagocytosis. The decrease in phagocytosis results in recurrent pyogenic ...

, 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

''Leucism'' is often used to describe the

phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (physical form and structure), its developmental processes, its biochemical and physiological propert ...

that results from defects in pigment cell differentiation and/or migration from the

neural crest The neural crest is a ridge-like structure that is formed transiently between the epidermal ectoderm and neural plate during vertebrate development. Neural crest cells originate from this structure through the epithelial-mesenchymal transition, ...

to skin, hair, or feathers during

development Development or developing may refer to: Arts *Development (music), the process by which thematic material is reshaped * Photographic development *Filmmaking, development phase, including finance and budgeting * Development hell, when a proje ...

. 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) having a lack of cells that can make

pigment A pigment is a powder used to add or alter color or change visual appearance. Pigments are completely or nearly solubility, insoluble and reactivity (chemistry), chemically unreactive in water or another medium; in contrast, dyes are colored sub ...

. Since all pigment cell-types differentiate from the same

multipotent Cell potency is a cell's ability to differentiate into other cell types. The more cell types a cell can differentiate into, the greater its potency. Potency is also described as the gene activation potential within a cell, which like a continuum ...

precursor cell-type, leucism can cause the reduction in all types of pigment. This is in contrast to

albinism Albinism is the congenital absence of melanin in an animal or plant resulting in white hair, feathers, scales and skin and reddish pink or blue eyes. Individuals with the condition are referred to as albinos. Varied use and interpretation of ...

, for which leucism is often mistaken. Albinism results in the reduction of

melanin Melanin (; ) is a family of biomolecules organized as oligomers or polymers, which among other functions provide the pigments of many organisms. Melanin pigments are produced in a specialized group of cells known as melanocytes. There are ...

production only, though the

melanocyte Melanocytes are melanin-producing neural-crest, neural crest-derived cell (biology), cells located in the bottom layer (the stratum basale) of the skin's epidermis (skin), epidermis, the middle layer of the eye (the uvea), the inner ear, vagina ...

(or melanophore) is still present. Thus in species that have other pigment cell-types, for example xanthophores, albinos are not entirely white, but instead display a pale yellow color. More common than a complete absence of pigment cells is localized or incomplete

hypopigmentation Hypopigmentation is characterized specifically as an area of Human skin, skin becoming lighter than the baseline skin color, but not completely devoid of skin pigment, pigment. This is not to be confused with depigmentation, which is characterize ...

, resulting in irregular patches of white on an animal that otherwise has normal coloring and patterning. This partial leucism is known as a "pied" or "

piebald A piebald or pied animal is one that has a pattern of unpigmented spots (white) on a pigmented background of hair, feathers or scales. Thus a piebald black and white dog is a black dog with white spots. The animal's skin under the white backg ...

" effect; and the ratio of white to normal-colured skin can vary considerably not only between generations, but between different offspring from the same parents, and even between members of the same litter. This is notable in

horse The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 mi ...

cow Cattle (''Bos taurus'') are large, domesticated, bovid ungulates widely kept as livestock. They are prominent modern members of the subfamily Bovinae and the most widespread species of the genus '' Bos''. Mature female cattle are called co ...

cat The cat (''Felis catus''), also referred to as the domestic cat or house cat, is a small domesticated carnivorous mammal. It is the only domesticated species of the family Felidae. Advances in archaeology and genetics have shown that the ...

dog The dog (''Canis familiaris'' or ''Canis lupus familiaris'') is a domesticated descendant of the gray wolf. Also called the domestic dog, it was selectively bred from a population of wolves during the Late Pleistocene by hunter-gatherers. ...

s, the urban

crow A crow is a bird of the genus ''Corvus'', or more broadly, a synonym for all of ''Corvus''. The word "crow" is used as part of the common name of many species. The related term "raven" is not linked scientifically to any certain trait but is rathe ...

and the ball python but is also found in many other species. Due to the lack of melanin production in both the

retina The retina (; or retinas) is the innermost, photosensitivity, light-sensitive layer of tissue (biology), tissue of the eye of most vertebrates and some Mollusca, molluscs. The optics of the eye create a focus (optics), focused two-dimensional ...

l pigmented epithelium (RPE) and iris, those affected by

sometimes have pink pupil due to the underlying blood vessels showing through. However, this is not always the case and many albino animals do not have pink pupils. The common belief that all albinos have pink pupils results in many albinos being incorrectly labeled as 'leucistic'. The neural crest disorders that cause leucism do not result in pink pupils and therefore most leucistic animals have normally colored eyes. This is because the melanocytes of the RPE do not derive from the

. Instead, an out-pouching of the

neural tube In the developing chordate (including vertebrates), the neural tube is the embryonic precursor to the central nervous system, which is made up of the brain and spinal cord. The neural groove gradually deepens as the neural folds become elevated, ...

generates the optic cup that, in turn, forms the

. As these cells are from an independent developmental origin, they are typically unaffected by the genetic cause of leucism.

Notable examples

Platypus The platypus (''Ornithorhynchus anatinus''), sometimes referred to as the duck-billed platypus, is a semiaquatic, egg-laying mammal endemic to eastern Australia, including Tasmania. The platypus is the sole living representative or monotypi ...

(''Ornithorhynchus anatinus'') – in 2021, a leucistic example was found in the Gwydir River, near

Armidale Armidale is a city in the Northern Tablelands, New South Wales, Australia. Armidale had a population of 23,967 as of the 2021 census. Estimated resident population, 30 June 2018. It is the administrative centre for the Northern Tablelands reg ...

New South Wales New South Wales (commonly abbreviated as NSW) is a States and territories of Australia, state on the Eastern states of Australia, east coast of :Australia. It borders Queensland to the north, Victoria (state), Victoria to the south, and South ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

.Rare white platypus in Gwydir River near Armidale is leucistic, researchers find
James Paras,

ABC News Online ABC News, also known as ABC News and Current Affairs, is a public news service produced by the Australian Broadcasting Corporation. The service covers both local and world affairs, broadcasting both nationally as ABC News, and across the Asia- ...

, 2023-11-03 * The Anchorage White Raven - a leucistic

common raven The common raven or northern raven (''Corvus corax'') is a large all-black passerine bird. It is the most widely distributed of all Corvidae, corvids, found across the Northern Hemisphere. There are 11 accepted subspecies with little variatio ...

known for its "trickster" behavior, spotted in 2023 and 2024 in

Anchorage, Alaska Anchorage, officially the Municipality of Anchorage, is the List of cities in Alaska, most populous city in the U.S. state of Alaska. With a population of 291,247 at the 2020 United States census, 2020 census, it contains nearly 40 percent of ...

Genetics

Gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

s that, when

mutated In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA replication, DNA or viral rep ...

, can cause leucism include '' c-kit'', '' mitf'' and '' EDNRB''.Waardenburg syndrome
at Atlas of Genetics and Cytogenetics in Oncology and Haematology (archived 26 December 2005, fro

accessed 18–22 July 2006).

Etymology

The terms ''leucistic'' and ''leucism'' are derived from the stem '' leuc-'' + ''

-ism ''-ism'' () is a suffix in many English grammar, English words, originally derived from the Ancient Greek suffix ('), and reached English language, English through the Latin , and the French language, French . It is used to create abstract noun ...

'', from Latin ''leuco-'' in turn derived from

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

λευκός (leukós) meaning ''white''.

Gallery

File:A Leucistic House Sparrow.jpg, A Leucistic House Sparrow in Kaycee, Wyoming USA File:Leucistic Texas Rat Snake.jpg, Leucistic Texas rat snake
('' Pantherophis obsoletus'') File:Common Grackle Leucistic.jpg, Leucistic

common grackle The common grackle (''Quiscalus quiscula'') is a species of large icterid bird found in large numbers through much of North America. First described in 1758 by Carl Linnaeus, the common grackle has three subspecies. Adult common grackles have a ...

('' Quiscalus quiscula'') File:Paon blanc Madère 2008.jpg, Leucistic Indian peacock
('' Pavo cristatus'') File:LeucisticAlligator.jpg, Leucistic American alligator
('' Alligator mississippiensis'') File:Leucistic white squirrel hanging on to a tree (85569).jpg, Leucistic eastern grey squirrel
('' Sciurus carolinensis'') File:Female Mallard with faded plumage at Bray Lock, May 2015.JPG, Leucistic female

mallard The mallard () or wild duck (''Anas platyrhynchos'') is a dabbling duck that breeds throughout the temperate and subtropical Americas, Eurasia, and North Africa. It has been introduced to New Zealand, Australia, Peru, Brazil, Uruguay, Arge ...

(''

Anas platyrhynchos The mallard () or wild duck (''Anas platyrhynchos'') is a dabbling duck that breeds throughout the temperate and subtropical Americas, Eurasia, and North Africa. It has been introduced to New Zealand, Australia, Peru, Brazil, Uruguay, Argen ...

'') File:20231001 house sparrow with incomplete leucism.jpg, Female

house sparrow The house sparrow (''Passer domesticus'') is a bird of the Old World sparrow, sparrow family Passeridae, found in most parts of the world. It is a small bird that has a typical length of and a mass of . Females and young birds are coloured pa ...

with incomplete leucism
(''

Passer domesticus The house sparrow (''Passer domesticus'') is a bird of the sparrow family Passeridae, found in most parts of the world. It is a small bird that has a typical length of and a mass of . Females and young birds are coloured pale brown and grey, ...

'') File:Leucismo parcial em Ramphastos toco (cropped).jpg,

Toco toucan The toco toucan (''Ramphastos toco'') is a species of bird in the toucan Family (biology), family Ramphastidae. It is the largest species of toucan and has a distinctive appearance, with a black body, a white throat, chest and uppertail-Covert ( ...

with partial leucism
('' Ramphastos toco'') File:Anchorage White Raven.jpg, The Anchorage White Raven, a common raven
('' Corvus corax'') File:The white duck of the Mandarins.jpg, Male

Mandarin duck The mandarin duck (''Aix galericulata'') is a perching duck species native to the East Palearctic. It is Sexual dimorphism, sexually dimorphic – the males are elaborately coloured, while the females have more subdued colours. It is a medium- ...

( Aix galericulata) (front)

References

External links

* {{Pigmentation disorders Animal coat colors Articles containing video clips Bird colours Dermatologic terminology Disturbances of pigmentation Genetic disorders with no OMIM