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Albinism (from Latin albus, "white"; see extended etymology) is a form of hypopigmentary congenital disorder, characterized by a partial (in hypomelanism, also known as hypomelanosis) or total (amelanism or amelanosis) lack of melanin pigment in the eyes, skin and hair (or more rarely the eyes alone). Albinism results from inheritance of recessive alleles. The condition is known to affect mammals (including humans), reptiles, amphibians, and insects. While the most common term for an organism affected by albinism is "albino" (noun and adjective), the word is sometimes used in derogatory ways towards people; the term "albinistic" (adjective) can be used to avoid the risk of being interpreted thus, while the politically correct term is "person with albinism" (noun). Additional clinical adjectives sometimes used to refer to animals are "albinoid" and "albinic".

Most humans and many animals with albinism appear white or very pale; the multiple types of melanin pigment are responsible for brown, black, gray, and some yellow colorations. In some animals, especially albinistic birds and reptiles, ruddy and yellow hues or other colors may be present on the entire body or in patches (as is common among pigeons), due to the presence of other pigments unaffected by albinism such as porphyrins, pteridines and psittacins, as well as carotenoid pigments derived from the diet. Some animals are white or pale due to chromatophore (pigment cell) defects, do not lack melanin production, and have normal eyes; they are referred to as leucistic.

The eyes of an animal with albinism occasionally appear red due to the underlying retinal blood vessels showing through where there is not enough pigment to cover them. In humans this is rarely the case, as a human eye is quite large and thus produces enough pigment to lend opacity to the eye, often colouring the iris pale blue. However, there are cases in which the eyes of an albinistic person appear red or purple, depending on the amount of pigment present. The albinistic are generally (but see related disorders below) as healthy as the rest of their species, with growth and development occurring as normal, and albinism by itself does not cause mortality (though the lack of pigment is an elevated risk for skin cancer and other problems.) Many animals with albinism lack their protective camouflage and are unable to conceal themselves from their predators or prey; the survival rate of animals with albinism in the wild is usually quite low. However the novelty of albino animals has occasionally led to their protection by groups such as the Albino Squirrel Preservation Society.

Albinism is a condition that cannot be "cured," but small things can be done to improve the quality of life for those affected. Most importantly to improve vision, protect the eyes from bright lights, and avoid skin damage from sunlight. The extent and success rate of these measures depend on the type of albinism and severity of the symptoms; in particular, people with ocular albinism are likely to have normally-pigmented skin, and thus do not need to take special precautions against skin damage.

For the most part, treatment of the eye conditions consists of visual rehabilitation. Surgery is possible on the ocular muscles to decrease nystagmus, strabismus and common refractive errors like astigmatism. Strabismus surgery may improve the appearance of the eyes.[citation needed] Nystagmus-damping surgery can also be performed, to reduce the "shaking" of the eyes back and forth. The effectiveness of all these procedures varies greatly and depends on individual circumstances. More importantly, since surgery will not restore a normal RPE or foveae, surgery will not provide fine binocular vision. In the case of esotropia (the "crossed eyes" form of strabismus), surgery may help vision by expanding the visual field (the area that the eyes can see while looking at one point).