Albinism
Overview
Albinism is a congenital disorder
Congenital disorder
A congenital disorder, or congenital disease, is a condition existing at birth and often before birth, or that develops during the first month of life , regardless of causation...

 characterized by the complete or partial absence of pigment
Biological pigment
Biological pigments, also known simply as pigments or biochromes are substances produced by living organisms that have a color resulting from selective color absorption. Biological pigments include plant pigments and flower pigments...

 in the skin, hair and eyes due to absence or defect of an enzyme involved in the production of melanin
Melanin
Melanin is a pigment that is ubiquitous in nature, being found in most organisms . In animals melanin pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms...

. Albinism results from inheritance of recessive gene alleles and is known to affect all vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s, including humans. While an organism with complete absence of melanin is called an albino (icon, or æ), an organism with only a diminished amount of melanin is described as albinoid.

Albinism is associated with a number of vision defects, such as photophobia
Photophobia
Photophobia is a symptom of abnormal intolerance to visual perception of light. As a medical symptom photophobia is not a morbid fear or phobia, but an experience of discomfort or pain to the eyes due to light exposure or by presence of actual physical photosensitivity of the eyes, though the term...

, Nystagmus
Nystagmus
Nystagmus is a condition of involuntary eye movement, acquired in infancy or later in life, that may result in reduced or limited vision.There are two key forms of Nystagmus: pathological and physiological, with variations within each type. Nystagmus may be caused by congenital disorders,...

 and astigmatism
Astigmatism
An optical system with astigmatism is one where rays that propagate in two perpendicular planes have different foci. If an optical system with astigmatism is used to form an image of a cross, the vertical and horizontal lines will be in sharp focus at two different distances...

.
Encyclopedia
Albinism is a congenital disorder
Congenital disorder
A congenital disorder, or congenital disease, is a condition existing at birth and often before birth, or that develops during the first month of life , regardless of causation...

 characterized by the complete or partial absence of pigment
Biological pigment
Biological pigments, also known simply as pigments or biochromes are substances produced by living organisms that have a color resulting from selective color absorption. Biological pigments include plant pigments and flower pigments...

 in the skin, hair and eyes due to absence or defect of an enzyme involved in the production of melanin
Melanin
Melanin is a pigment that is ubiquitous in nature, being found in most organisms . In animals melanin pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms...

. Albinism results from inheritance of recessive gene alleles and is known to affect all vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s, including humans. While an organism with complete absence of melanin is called an albino (icon, or æ), an organism with only a diminished amount of melanin is described as albinoid.

Albinism is associated with a number of vision defects, such as photophobia
Photophobia
Photophobia is a symptom of abnormal intolerance to visual perception of light. As a medical symptom photophobia is not a morbid fear or phobia, but an experience of discomfort or pain to the eyes due to light exposure or by presence of actual physical photosensitivity of the eyes, though the term...

, Nystagmus
Nystagmus
Nystagmus is a condition of involuntary eye movement, acquired in infancy or later in life, that may result in reduced or limited vision.There are two key forms of Nystagmus: pathological and physiological, with variations within each type. Nystagmus may be caused by congenital disorders,...

 and astigmatism
Astigmatism
An optical system with astigmatism is one where rays that propagate in two perpendicular planes have different foci. If an optical system with astigmatism is used to form an image of a cross, the vertical and horizontal lines will be in sharp focus at two different distances...

. Lack of skin pigmentation makes the organism more susceptible to sunburn and skin cancers.

Classification in humans

Albinism (from Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 albus, "white"; see extended etymology, also called achromia, achromasia, or achromatosis) is a congenital disorder
Congenital disorder
A congenital disorder, or congenital disease, is a condition existing at birth and often before birth, or that develops during the first month of life , regardless of causation...

 characterized by the complete or partial absence of pigment
Biological pigment
Biological pigments, also known simply as pigments or biochromes are substances produced by living organisms that have a color resulting from selective color absorption. Biological pigments include plant pigments and flower pigments...

 in the skin, hair and eyes due to absence or defect of an enzyme involved in the production of melanin
Melanin
Melanin is a pigment that is ubiquitous in nature, being found in most organisms . In animals melanin pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms...

. Albinism results from inheritance of recessive gene alleles and is known to affect all vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s, including humans. While an organism with complete absence of melanin is called an albino (icon, or æ), an organism with only a diminished amount of melanin is described as albinoid.

Albinism is associated with a number of vision defects, such as photophobia
Photophobia
Photophobia is a symptom of abnormal intolerance to visual perception of light. As a medical symptom photophobia is not a morbid fear or phobia, but an experience of discomfort or pain to the eyes due to light exposure or by presence of actual physical photosensitivity of the eyes, though the term...

, Nystagmus
Nystagmus
Nystagmus is a condition of involuntary eye movement, acquired in infancy or later in life, that may result in reduced or limited vision.There are two key forms of Nystagmus: pathological and physiological, with variations within each type. Nystagmus may be caused by congenital disorders,...

 and astigmatism
Astigmatism
An optical system with astigmatism is one where rays that propagate in two perpendicular planes have different foci. If an optical system with astigmatism is used to form an image of a cross, the vertical and horizontal lines will be in sharp focus at two different distances...

. Lack of skin pigmentation makes the organism more susceptible to sunburn and skin cancers.

Classification in humans

Albinism (from Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 albus, "white"; see extended etymology, also called achromia, achromasia, or achromatosis) is a congenital disorder
Congenital disorder
A congenital disorder, or congenital disease, is a condition existing at birth and often before birth, or that develops during the first month of life , regardless of causation...

 characterized by the complete or partial absence of pigment
Biological pigment
Biological pigments, also known simply as pigments or biochromes are substances produced by living organisms that have a color resulting from selective color absorption. Biological pigments include plant pigments and flower pigments...

 in the skin, hair and eyes due to absence or defect of an enzyme involved in the production of melanin
Melanin
Melanin is a pigment that is ubiquitous in nature, being found in most organisms . In animals melanin pigments are derivatives of the amino acid tyrosine. The most common form of biological melanin is eumelanin, a brown-black polymer of dihydroxyindole carboxylic acids, and their reduced forms...

. Albinism results from inheritance of recessive gene alleles and is known to affect all vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

s, including humans. While an organism with complete absence of melanin is called an albino (icon, or æ), an organism with only a diminished amount of melanin is described as albinoid.

Albinism is associated with a number of vision defects, such as photophobia
Photophobia
Photophobia is a symptom of abnormal intolerance to visual perception of light. As a medical symptom photophobia is not a morbid fear or phobia, but an experience of discomfort or pain to the eyes due to light exposure or by presence of actual physical photosensitivity of the eyes, though the term...

, Nystagmus
Nystagmus
Nystagmus is a condition of involuntary eye movement, acquired in infancy or later in life, that may result in reduced or limited vision.There are two key forms of Nystagmus: pathological and physiological, with variations within each type. Nystagmus may be caused by congenital disorders,...

 and astigmatism
Astigmatism
An optical system with astigmatism is one where rays that propagate in two perpendicular planes have different foci. If an optical system with astigmatism is used to form an image of a cross, the vertical and horizontal lines will be in sharp focus at two different distances...

. Lack of skin pigmentation makes the organism more susceptible to sunburn and skin cancers.

Classification in humans


There are two main categories of albinism in humans:
  • In oculocutaneous albinism
    Oculocutaneous albinism
    Oculocutaneous albinism is a form of albinism involving the eyes , skin , and in rare instances, the hair as well.Four types of oculocutaneous albinism have been described, all caused by a disruption of melanin synthesis and all autosomal recessive disorders.Common Albinism requires genes from both...

     Types 1-4 with different levels with pigmentation
    (despite its Latin-derived name meaning "eye-and-skin" albinism), pigment is lacking in the eyes, skin and hair. (The equivalent mutation in non-humans also results in lack of melanin in the fur, scales or feathers.) People with oculocutaneous albinism can have anything from no pigment at all to almost normal levels for a rather pale Caucasian.
  • In ocular albinism
    Ocular albinism
    Ocular albinism is a form of albinism which, in contrast to oculocutaneous albinism, presents primarily in the eyes. There are multiple forms of ocular albinism, which are clinically similar.Both known genes are on the X chromosome...

    , only the eyes lack pigment. People who have ocular albinism have generally normal skin and hair color, although it is typically lighter than either parent. Many even have a normal eye appearance. Also, ocular albinism is generally sex-linked, therefore males are more likely to be affected. Males are without another X chromosome to mask recessive alleles on the X they inherit.


Other conditions include albinism as part of their presentation. These include Hermansky-Pudlak syndrome
Hermansky-Pudlak syndrome
Hermansky–Pudlak syndrome is a rare autosomal recessive disorder which results in oculocutaneous albinism , bleeding problems due to a platelet abnormality , and storage of an abnormal fat-protein compound .There are eight classic forms of the disorder, based on the genetic mutation...

, Chediak-Higashi syndrome
Chédiak-Higashi syndrome
Chédiak–Higashi syndrome is a rare autosomal recessive disorder that arises from a microtubule polymerization defect which leads to a decrease in phagocytosis. The decrease in phagocytosis results in recurrent pyogenic infections, partial albinism and peripheral neuropathy...

, Griscelli syndrome
Griscelli syndrome
Griscelli syndrome is a rare autosomal recessive disorder characterized by albinism with immunodeficiency, that usually causes death by early childhood.-Types:...

, Waardenburg syndrome
Waardenburg syndrome
Waardenburg syndrome Waardenburg syndrome Waardenburg syndrome (also Waardenburg­ Shah Syndrome, Waardenburg-Klein syndrome, Mende's syndrome II, Van der Hoeve-Halbertsma-Waardenburg syndrome, Ptosis-Epicanthus syndrome, Van der Hoeve-Halbertsma-Gualdi syndrome, Waardenburg type Pierpont,[5] Van...

, and Tietz syndrome
Tietz syndrome
Tietz syndrome, also called Tietz albinism-deafness syndrome or albinism and deafness of Tietz, is an autosomal dominant congenital disorder characterized by deafness and leucism. It is caused by a mutation in the microphthalmia-associated transcription factor gene...

. These conditions are sometimes classified with albinism. Several have sub-types. Some are easily distinguished by appearance, but in most cases genetic testing is the only way to be certain.

Albinism was formerly categorized as tyrosinase
Tyrosinase
Tyrosinase also known as monophenol monooxygenase is an enzyme that catalyses the oxidation of phenols and is widespread in plants and animals...

-positive or -negative. In cases of tyrosinase-positive albinism, the enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 tyrosinase is present. The melanocyte
Melanocyte
-External links: - "Eye: fovea, RPE" - "Integument: pigmented skin"...

s (pigment cells) are unable to produce melanin for any one of a variety of reasons that do not directly involve the tyrosinase enzyme. In tyrosinase-negative cases, either the tyrosinase enzyme is not produced or a nonfunctional version is produced. This classification has been rendered obsolete by recent research.

Signs and symptoms

Most albinistic humans appear white or very pale as the melanin pigments responsible for brown, black, and some yellow colorations are not present.

Because individuals with albinism have skin that partially or entirely lacks the dark pigment melanin, which helps protect the skin from the sun's ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...

 radiation
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...

, their skin can burn
Sunburn
A sunburn is a burn to living tissue, such as skin, which is produced by overexposure to ultraviolet radiation, commonly from the sun's rays. Usual mild symptoms in humans and other animals include red or reddish skin that is hot to the touch, general fatigue, and mild dizziness. An excess of UV...

 more easily from overexposure.

The human eye normally produces enough pigment to color the iris and lend opacity to the eye. However, there are cases in which the eyes of an albinistic person appear red or purple, depending on the amount of pigment present. Lack of pigment in the eyes also results in problems with vision, both related and unrelated to photosensitivity
Photosensitivity
Photosensitivity is the amount to which an object reacts upon receiving photons, especially visible light.- Human medicine :Sensitivity of the skin to a light source can take various forms. People with particular skin types are more sensitive to sunburn...

.

The albinistic are generally as healthy as the rest of the population (but see related disorders below), with growth and development occurring as normal, and albinism by itself does not cause mortality, although the lack of pigment blocking ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...

 radiation
Radiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...

 increases the risk of skin cancer and other problems.

Visual problems

Development of the optical system is highly dependent on the presence of melanin, and the reduction or absence of this pigment in albinistic individuals may lead to
  • Misrouting of the retinogeniculate projections, resulting in abnormal decussation
    Decussation
    Decussation is used in biological contexts to describe a crossing.Examples include:* In the brain, where nerve fibers obliquely cross from one lateral part to the other, that is to say they cross at a level other than their origin...

     (crossing) of optic nerve fibres
  • Photophobia
    Photophobia
    Photophobia is a symptom of abnormal intolerance to visual perception of light. As a medical symptom photophobia is not a morbid fear or phobia, but an experience of discomfort or pain to the eyes due to light exposure or by presence of actual physical photosensitivity of the eyes, though the term...

     and decreased visual acuity
    Visual acuity
    Visual acuity is acuteness or clearness of vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain....

     due to light scattering within the eye (ocular straylight
    Ocular straylight
    Ocular straylight is the unwanted effect of light spreading as seen by human eyes, and caused by the eye itself, not by external factors. It is most easily visualized as the radiation seen spreading from a bright light source against a dark background. The typical practical example is an opposing...

    )
  • Reduced visual acuity due to foveal hypoplasia
    Macular hypoplasia
    Macular hypoplasia, also known as fovea hypoplasia, is a rare medical condition involving the underdevelopment of the macula, a small area on the retina responsible for seeing in detail. Macular hypoplasia is often associated with albinism.-External links:*...

     and possibly light-induced retina
    Retina
    The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...

    l damage


Eye conditions common in albinism include:
  • Nystagmus
    Nystagmus
    Nystagmus is a condition of involuntary eye movement, acquired in infancy or later in life, that may result in reduced or limited vision.There are two key forms of Nystagmus: pathological and physiological, with variations within each type. Nystagmus may be caused by congenital disorders,...

    , irregular rapid movement of the eyes back and forth, or in circular motion.
  • Refractive errors such as myopia
    Myopia
    Myopia , "shortsightedness" ) is a refractive defect of the eye in which collimated light produces image focus in front of the retina under conditions of accommodation. In simpler terms, myopia is a condition of the eye where the light that comes in does not directly focus on the retina but in...

     or hyperopia
    Hyperopia
    Hyperopia, also known as farsightedness, longsightedness or hypermetropia, is a defect of vision caused by an imperfection in the eye , causing difficulty focusing on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance...

     and especially astigmatism
    Astigmatism (eye)
    Astigmatism is an optical defect in which vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image on the retina. This may be due to an irregular or toric curvature of the cornea or lens. There are two types of astigmatism: regular and...

  • Amblyopia
    Amblyopia
    Amblyopia, also known as lazy eye, is a disorder of the visual system that is characterized by a vision deficiency in an eye that is otherwise physically normal, or out of proportion to associated structural abnormalities of the eye...

    , decrease in acuity of one or both eyes due to poor transmission to the brain, often due to other conditions such as strabismus
    Strabismus
    Strabismus is a condition in which the eyes are not properly aligned with each other. It typically involves a lack of coordination between the extraocular muscles, which prevents bringing the gaze of each eye to the same point in space and preventing proper binocular vision, which may adversely...

    .
  • Optic nerve hypoplasia
    Optic nerve hypoplasia
    Optic nerve hypoplasia is a medical condition arising from the underdevelopment of the optic nerve. This condition is the most common congenital optic nerve anomaly. The optic disc appears abnormally small, because not all the optic nerve axons have developed properly...

    , underdevelopment of the optic nerve


Some of the visual problems associated with albinism arise from a poorly developed retinal pigment epithelium (RPE) due to the lack of melanin. This degenerate RPE causes foveal hypoplasia (a failure in the development of normal fovea
Fovea
The fovea centralis, also generally known as the fovea , is a part of the eye, located in the center of the macula region of the retina....

e), which results in eccentric fixation and lower visual acuity, and often a minor level of strabismus.

The iris
Iris (anatomy)
The iris is a thin, circular structure in the eye, responsible for controlling the diameter and size of the pupils and thus the amount of light reaching the retina. "Eye color" is the color of the iris, which can be green, blue, or brown. In some cases it can be hazel , grey, violet, or even pink...

 is a sphincter
Sphincter
A sphincter is an anatomical structure, or a circular muscle, that normally maintains constriction of a natural body passage or orifice and which relaxes as required by normal physiological functioning...

 formed from pigmented tissue that contracts when the eye is exposed to bright light, to protect the retina
Retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...

 by limiting the amount of light passing through the pupil. In low light conditions the iris relaxes to allow more light to enter the eye. In albinistic subjects, the iris does not have enough pigment to block the light, thus the decrease in pupil diameter is only partially successful in reducing the amount of light entering the eye. Additionally, the improper development of the RPE, which in normal eyes absorbs most of the reflected sunlight, further increases glare due to light scattering within the eye. The resulting sensitivity (photophobia) generally leads to discomfort in bright light, but this can be reduced by the use of sunglasses and/or brimmed hats.

Genetics

Most forms of albinism are the result of the biological inheritance of genetically recessive
Dominance relationship
Dominance in genetics is a relationship between two variant forms of a single gene, in which one allele masks the effect of the other in influencing some trait. In the simplest case, if a gene exists in two allelic forms , three combinations of alleles are possible: AA, AB, and BB...

 allele
Allele
An allele is one of two or more forms of a gene or a genetic locus . "Allel" is an abbreviation of allelomorph. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation...

s (gene
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

s) passed from both parents of an individual, though some rare forms are inherited from only one parent. There are other genetic mutations which are proven to be associated with albinism. All alterations, however, lead to changes in melanin production in the body.

The chance of offspring with albinism resulting from the pairing of an organism with albinism and one without albinism is low. However, because organisms can be carriers of genes for albinism without exhibiting any traits, albinistic offspring can be produced by two non-albinistic parents. Albinism usually occurs with equal frequency in both genders. An exception to this is ocular albinism, which it is passed on to offspring through X-linked inheritance. Thus, ocular albinism occurs more frequently in males as they have a single X and Y chromosome, unlike females, whose genetics are characterized by two X chromosomes.

There are two different forms of albinism; a partial lack of the melanin is known as hypomelanism, or hypomelanosis and the total absence of melanin is known as amelanism
Amelanism
Amelanism is a pigmentation abnormality characterized by the lack of pigments called melanins, commonly associated with a genetic loss of tyrosinase function. Amelanism can affect fish, amphibians, reptiles, birds, and mammals including humans. The appearance of an amelanistic animal depends on...

 or amelanosis.

Diagnosis

Genetic testing
Genetic testing
Genetic testing is among the newest and most sophisticated of techniques used to test for genetic disorders which involves direct examination of the DNA molecule itself. Other genetic tests include biochemical tests for such gene products as enzymes and other proteins and for microscopic...

 can confirm albinism and what variety it is, but offers no medical benefits except in the cases of non-OCA disorders (see below) that cause albinism along with other medical problems which may be treatable. The symptoms of albinism can be treated by various methods detailed below.

Treatment

For the most part, treatment of the eye conditions consists of visual rehabilitation. Surgery is possible on the ocular muscles to decrease nystagmus, strabismus
Strabismus
Strabismus is a condition in which the eyes are not properly aligned with each other. It typically involves a lack of coordination between the extraocular muscles, which prevents bringing the gaze of each eye to the same point in space and preventing proper binocular vision, which may adversely...

 and common refractive errors like astigmatism
Astigmatism (eye)
Astigmatism is an optical defect in which vision is blurred due to the inability of the optics of the eye to focus a point object into a sharp focused image on the retina. This may be due to an irregular or toric curvature of the cornea or lens. There are two types of astigmatism: regular and...

. Strabismus surgery may improve the appearance of the eyes. 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
Esotropia
Esotropia is a form of strabismus, or "squint", in which one or both eyes turns inward. The condition can be constantly present, or occur intermittently, and can give the affected individual a "cross-eyed" appearance...

 (the "crossed eyes" form of strabismus), surgery may help vision by expanding the visual field
Visual field
The term visual field is sometimes used as a synonym to field of view, though they do not designate the same thing. The visual field is the "spatial array of visual sensations available to observation in introspectionist psychological experiments", while 'field of view' "refers to the physical...

 (the area that the eyes can see while looking at one point).

Glasses
Glasses
Glasses, also known as eyeglasses , spectacles or simply specs , are frames bearing lenses worn in front of the eyes. They are normally used for vision correction or eye protection. Safety glasses are a kind of eye protection against flying debris or against visible and near visible light or...

 and other vision aids, large-print materials and CCTV, as well as bright but angled reading lights, can help individuals with albinism, even though their vision cannot be corrected completely. Some people with Albinism do well using bifocals
Bifocals
Bifocals are eyeglasses with two distinct optical powers. Bifocals are most commonly prescribed to people with presbyopia who also require a correction for myopia, hyperopia, and/or astigmatism.-History:...

 (with a strong reading lens), prescription reading glasses, and/or hand-held devices such as magnifiers
Magnifying glass
A magnifying glass is a convex lens that is used to produce a magnified image of an object. The lens is usually mounted in a frame with a handle ....

 or monocular
Monocular
A monocular is a modified refracting telescope used to magnify the images of distant objects by passing light through a series of lenses and sometimes prisms; the use of prisms results in a lightweight telescope. Volume and weight are less than half those of binoculars of similar optical...

s (a very simple telescope). Contact lenses may be colored to block light transmission through the iris. But in case of nystagmus this is not possible, due to the irritation that is caused by the movement of the eyes. Some use bioptics
Bioptics (device)
Bioptics, also known as a bioptic in the singular, and sometimes more formally termed a bioptic telescope, is a term for a pair of vision-enhancement lenses with extreme magnification, used to improve distance vision for those with severely impaired eyesight, especially those with albinism...

, glasses which have small telescopes mounted on, in, or behind their regular lenses, so that they can look through either the regular lens or the telescope. Newer designs of bioptics use smaller light-weight lenses. Some US states allow the use of bioptic telescopes for driving motor vehicles. (See also NOAH
National Organization for Albinism and Hypopigmentation
The National Organization for Albinism and Hypopigmentation is a non-profit organization that assists people who have albinism. NOAH was created in 1982 and is based in East Hampstead, New Hampshire....

 bulletin "Low Vision Aids".)

Epidemiology

Albinism affects people of all ethnic backgrounds; its frequency worldwide is estimated to be approximately one in 17,000. Prevalence of the different forms of albinism varies considerably by population, and is highest overall in people of sub-Saharan African descent.

Society and culture



In physical terms, humans with albinism commonly have vision problems and need sun protection. But they also face social
Society
A society, or a human society, is a group of people related to each other through persistent relations, or a large social grouping sharing the same geographical or virtual territory, subject to the same political authority and dominant cultural expectations...

 and cultural
Culture
Culture is a term that has many different inter-related meanings. For example, in 1952, Alfred Kroeber and Clyde Kluckhohn compiled a list of 164 definitions of "culture" in Culture: A Critical Review of Concepts and Definitions...

 challenges (even threats) as the condition is often a source of ridicule, discrimination, or even fear and violence. Cultures around the world have developed many beliefs regarding people with albinism. This folklore ranges from harmless myth to dangerous superstitions that cost human lives. Cultural challenges can be expected to be vastly higher in areas where pale skin and light hair stand out more from the ethnic majority's average phenotype.

In African countries such as Tanzania
Tanzania
The United Republic of Tanzania is a country in East Africa bordered by Kenya and Uganda to the north, Rwanda, Burundi, and the Democratic Republic of the Congo to the west, and Zambia, Malawi, and Mozambique to the south. The country's eastern borders lie on the Indian Ocean.Tanzania is a state...

 and Burundi
Burundi
Burundi , officially the Republic of Burundi , is a landlocked country in the Great Lakes region of Eastern Africa bordered by Rwanda to the north, Tanzania to the east and south, and the Democratic Republic of the Congo to the west. Its capital is Bujumbura...

, there has been an unprecedented rise in witchcraft
Witchcraft
Witchcraft, in historical, anthropological, religious, and mythological contexts, is the alleged use of supernatural or magical powers. A witch is a practitioner of witchcraft...

-related killings of albino people in recent years. This is because albino body parts are used in potions sold by witchdoctor
Witchdoctor
Erin Johnson, better known as Witchdoctor, is an established member of Atlanta’s Dungeon Family collective which includes members such as Goodie Mob, OutKast, Cee-Lo , Big Rube, & many others...

s. Numerous authenticated incidents have occurred in Africa during the 21st Century. For example, in Tanzania, in September 2009, three men were convicted of killing a 14-year-old albino boy and severing his legs in order to sell them for witchcraft purposes. Again in Tanzania and Burundi in 2010, the murder and dismemberment of a kidnapped albino child is reported from the courts, as part of a continuing problem.

Other examples: In Zimbabwe
Zimbabwe
Zimbabwe is a landlocked country located in the southern part of the African continent, between the Zambezi and Limpopo rivers. It is bordered by South Africa to the south, Botswana to the southwest, Zambia and a tip of Namibia to the northwest and Mozambique to the east. Zimbabwe has three...

, belief that sex with an albinistic woman will cure a man of HIV
HIV
Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...

 has led to rape
Rape
Rape is a type of sexual assault usually involving sexual intercourse, which is initiated by one or more persons against another person without that person's consent. The act may be carried out by physical force, coercion, abuse of authority or with a person who is incapable of valid consent. The...

s (and subsequent HIV infection).

Certain ethnic groups and insular areas exhibit heightened susceptibility to albinism, presumably due to genetic factors (reinforced by cultural traditions). These include notably the Native American
Indigenous peoples of the Americas
The indigenous peoples of the Americas are the pre-Columbian inhabitants of North and South America, their descendants and other ethnic groups who are identified with those peoples. Indigenous peoples are known in Canada as Aboriginal peoples, and in the United States as Native Americans...

 Kuna
Kuna (people)
Kuna or Cuna is the name of an indigenous people of Panama and Colombia. The spelling Kuna is currently preferred. In the Kuna language, the name is Dule or Tule, meaning "people," and the name of the language in Kuna is Dulegaya, meaning "Kuna language" - Location :The Kuna live in three...

 and Zuni nations (respectively of Panama
Panama
Panama , officially the Republic of Panama , is the southernmost country of Central America. Situated on the isthmus connecting North and South America, it is bordered by Costa Rica to the northwest, Colombia to the southeast, the Caribbean Sea to the north and the Pacific Ocean to the south. The...

 and New Mexico
New Mexico
New Mexico is a state located in the southwest and western regions of the United States. New Mexico is also usually considered one of the Mountain States. With a population density of 16 per square mile, New Mexico is the sixth-most sparsely inhabited U.S...

); Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

, in which one particular form of albinism is unusually common; and Ukerewe Island
Ukerewe Island
Ukerewe is the largest island in Lake Victoria and the largest inland island in Africa, with an area of approximately 530 km². Part of Tanzania, and location of the Ukerewe District, it is situated 45 km north of Mwanza to which it is linked by ferry, but a shorter vehicle ferry crossing of only...

, the population of which shows a very high incidence of albinism.

A number of people with albinism have become famous, including historical figures such as Emperor Seinei
Emperor Seinei
was the 22nd emperor of Japan, according to the traditional order of succession.No firm dates can be assigned to this emperor's life or reign, but he is conventionally considered to have reigned from 480–484.-Legendary narrative:...

 of Japan, and Oxford don William Archibald Spooner
William Archibald Spooner
William Archibald Spooner was a famous Oxford don whose name is given to the linguistic phenomenon of spoonerism.-Biography:...

; actor-comedian Victor Varnado
Victor Varnado
Victor Varnado is an American standup comedian and actor. Born in Gary, Indiana, he is African American and albinistic. He was born legally blind due to his Albinism...

; musicians such as Johnny
Johnny Winter
John Dawson "Johnny" Winter III is an American blues guitarist, singer, and producer. Best known for his late 1960s and 1970s high-energy blues-rock albums and live performances, Winter also produced three Grammy Award-winning albums for blues legend Muddy Waters...

 and Edgar Winter
Edgar Winter
Edgar Holland Winter is an American musician. He is famous for being a multi-instrumentalist. He is a highly skilled keyboardist, saxophonist and percussionist. He often plays an instrument while singing. He was most successful in the 1970s with his band, The Edgar Winter Group, notably with their...

, Salif Keita
Salif Keita
Salif Keïta is an internationally recognized afro-pop singer-songwriter from Mali. He is unique not only because of his reputation as the Golden Voice of Africa, but because he has albinism and is a direct descendant of the founder of the Mali Empire, Sundiata Keita...

, Winston "Yellowman" Foster
Yellowman
Yellowman is a Jamaican reggae and dancehall deejay, widely known as King Yellowman...

, Brother Ali
Brother Ali
Ali Newman , better known by the stage name Brother Ali, is an American hip hop artist signed to Rhymesayers Entertainment.-Personal life:...

, Sivuca
Sivuca
Severino Dias de Oliveirawas a Brazilian accordionist and guitarist.In addition to in his home state of Paraíba, in Recife, and in Rio de Janeiro,...

, Willie "Piano Red" Perryman
Piano Red
William "Willie" Lee Perryman , usually known professionally as Piano Red and later in life as Dr. Feelgood, was an American blues musician, the first to hit the pop music charts. He was a self-taught pianist who played in the barrelhouse blues style...

; and fashion model Connie Chiu
Connie Chiu
Connie Chiu was the world's first albinistic fashion model.Chiu was born in Hong Kong to a Chinese family. Like many people with albinism, she has to protect her photosensitive eyes and skin from the sunlight...

.

There have also been some famed albino animals, including Migaloo, a humpback whale
Humpback Whale
The humpback whale is a species of baleen whale. One of the larger rorqual species, adults range in length from and weigh approximately . The humpback has a distinctive body shape, with unusually long pectoral fins and a knobbly head. It is an acrobatic animal, often breaching and slapping the...

 off the coast of Australia; an albino Bottlenose dolphin named Pinky
Pinky (dolphin)
Pinky is an albino bottlenose dolphin found in Calcasieu Lake, Louisiana.Pinky was first spotted in 2007 by a boat caftain, Erik Rue. The dolphin has become a tourist attraction, and conservationists have asked visitors to leave the dolphin alone....

 living in & around in Calcasieu Lake, Louisiana, Snowflake, a gorilla
Gorilla
Gorillas are the largest extant species of primates. They are ground-dwelling, predominantly herbivorous apes that inhabit the forests of central Africa. Gorillas are divided into two species and either four or five subspecies...

 from a zoo in Barcelona
Barcelona
Barcelona is the second largest city in Spain after Madrid, and the capital of Catalonia, with a population of 1,621,537 within its administrative limits on a land area of...

; Snowdrop
Snowdrop
Galanthus is a small genus of about 20 species of bulbous herbaceous plants in the Amaryllis family, subfamily Amaryllidoideae...

, a Bristol Zoo
Bristol Zoo
Bristol Zoo is a zoo in the city of Bristol in South West England. The zoo's stated mission is "Bristol Zoo Gardens maintains and defends biodiversity through breeding endangered species, conserving threatened species and habitats and promoting a wider understanding of the natural...

 penguin
Penguin
Penguins are a group of aquatic, flightless birds living almost exclusively in the southern hemisphere, especially in Antarctica. Highly adapted for life in the water, penguins have countershaded dark and white plumage, and their wings have become flippers...

; and an albino buffalo known as Mahpiya Ska which is Sioux for White Cloud, in Jamestown, ND. and the sperm whale
Sperm Whale
The sperm whale, Physeter macrocephalus, is a marine mammal species, order Cetacea, a toothed whale having the largest brain of any animal. The name comes from the milky-white waxy substance, spermaceti, found in the animal's head. The sperm whale is the only living member of genus Physeter...

 Mocha Dick
Mocha Dick
Mocha Dick was a notorious male sperm whale that lived in the Pacific Ocean in the early 19th century, usually encountered in the waters near the island of Mocha, off southern Chile. American explorer and author Jeremiah N. Reynolds published his account, "Mocha Dick: Or The White Whale of the...

, the inspiration for Herman Melville
Herman Melville
Herman Melville was an American novelist, short story writer, essayist, and poet. He is best known for his novel Moby-Dick and the posthumous novella Billy Budd....

's novel Moby-Dick
Moby-Dick
Moby-Dick; or, The Whale, was written by American author Herman Melville and first published in 1851. It is considered by some to be a Great American Novel and a treasure of world literature. The story tells the adventures of wandering sailor Ishmael, and his voyage on the whaleship Pequod,...

.

In other animals

Many animals with albinism lack their protective camouflage
Camouflage
Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...

 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
Albino Squirrel Preservation Society
The Albino Squirrel Preservation Society is an international collegiate organization dedicated to "fostering compassion and goodwill" toward albino squirrels...

.

In partial albinism there can be a single patch or patches of skin that lack melanin. Especially in albinistic birds
Albinism in birds
Albinism in birds is rare, occurring to any extent in perhaps one in 1800 individuals . A bird that is albino has white feathers in place of coloured ones on some portion of its body...

 and reptiles, ruddy and yellow hues or other colors may be present on the entire body or in patches (as is common among pigeons), because of the presence of other pigments unaffected by albinism such as porphyrin
Porphyrin
Porphyrins are a group of organic compounds, many naturally occurring. One of the best-known porphyrins is heme, the pigment in red blood cells; heme is a cofactor of the protein hemoglobin. Porphyrins are heterocyclic macrocycles composed of four modified pyrrole subunits interconnected at...

s, pteridine
Pteridine
Pteridine is a chemical compound composed of fused pyrimidine and pyrazine rings. A pteridine is also a group of heterocyclic compounds containing a wide variety of substitutions on this structure. Pterins and flavins are classes of substituted pteridines that have important biological...

s and psittacins, as well as carotenoid
Carotenoid
Carotenoids are tetraterpenoid organic pigments that are naturally occurring in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms like algae, some bacteria, and some types of fungus. Carotenoids can be synthesized fats and other basic organic metabolic building...

 pigments derived from the diet.

In some animals albinism-like conditions may affect other pigments or pigment-production mechanisms:
  • "Whiteface" a condition that affect some parrot species is caused by a lack of psittacins.
  • Axanthism is a condition common in reptiles and amphibians, in which xanthophore metabolism
    Metabolism
    Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

     is affected rather than synthesis
    Chemical synthesis
    In chemistry, chemical synthesis is purposeful execution of chemical reactions to get a product, or several products. This happens by physical and chemical manipulations usually involving one or more reactions...

     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 color. Some leucistic animals are white or pale because of chromatophore
    Chromatophore
    Chromatophores are pigment-containing and light-reflecting cells found in amphibians, fish, reptiles, crustaceans, and cephalopods. They are largely responsible for generating skin and eye colour in cold-blooded animals and are generated in the neural crest during embryonic development...

     (pigment cell) defects, and do not lack melanin.
  • Melanism
    Melanism
    Melanism is an undue development of dark-colored pigment in the skin or its appendages, and the opposite of albinism. It is also the medical term for black jaundice.The word is deduced from the , meaning black pigment....

     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 genepool.


Intentionally bred albinistic strains of some animal species are commonly used as model organism
Model organism
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...

s in biomedical study and experimentation, although some researchers have argued that they are not always the best choice. Examples include the BALB/c
BALB/c
BALB/c is an albino, laboratory-bred strain of the House Mouse from which a number of common substrains are derived. Now over 200 generations from their origin in New York in 1920, BALB/c mice are distributed globally, and are among the most widely used inbred strains used in animal...

 mouse and Wistar and Sprague Dawley rat strains, while albino rabbits were historically used for Draize toxicity testing
Draize test
The Draize Test is an acute toxicity test devised in 1944 by Food and Drug Administration toxicologists John H. Draize and Jacob M. Spines...

. The yellow mutation in fruit flies
Drosophila
Drosophila is a genus of small flies, belonging to the family Drosophilidae, whose members are often called "fruit flies" or more appropriately pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species to linger around overripe or rotting fruit...

 is their version of albinism.

The incidence of albinism can be artificially increased in fish by exposing the eggs to heavy metals
Heavy metals
A heavy metal is a member of a loosely-defined subset of elements that exhibit metallic properties. It mainly includes the transition metals, some metalloids, lanthanides, and actinides. Many different definitions have been proposed—some based on density, some on atomic number or atomic weight,...

 (arsenic, cadmium, copper, mercury, selenium, zinc).

The eyes of an albino animal appear red because the colour of the red blood cells in the underlying retinal blood vessels shows through where there is no pigment to obscure it.

See also

  • Albinism–deafness syndrome
    Albinism–deafness syndrome
    Albinism–deafness syndrome is a condition characterized by congenital neural deafness and a severe or extreme piebald-like phenotype with extensive areas of hypopigmentation....

  • Vitiligo
    Vitiligo
    Vitiligo is a condition that causes depigmentation of sections of skin. It occurs when melanocytes, the cells responsible for skin pigmentation, die or are unable to function. The cause of vitiligo is unknown, but research suggests that it may arise from autoimmune, genetic, oxidative stress,...

     (or leukoderma), patchy loss of dermal pigmentation
  • Piebaldism
    Piebaldism
    Piebaldism is a rare autosomal dominant disorder of melanocyte development. Common characteristics include a congenital white forelock, scattered normal pigmented and hypopigmented macules and a triangular shaped depigmented patch on the forehead....

    , patchy alternating loss of and concentrations of dermal pigmentation
  • Xanthochromism and axanthism
    Xanthochromism
    Xanthochromism is a term that may be applied to birds, fish and other animals whose colouration is unusually yellow through an excess of yellow pigment, or possibly a loss of darker pigments that allows yellow pigment to be unusually dominant...

    , unusually yellow pigmentation and lack of yellow pigment, respectively
  • Erythrism
    Erythrism
    Erythrism or erythrochroism refers to an unusual reddish pigmentation of an animal's fur, hair, skin, feathers, or eggshells.Causes of erythrism include*genetic mutations which cause an absence of a normal pigment and/or excessive production of others...

    , unusually red pigmentation
  • Nevus
    Nevus
    Nevus is the medical term for sharply-circumscribed and chronic lesions of the skin. These lesions are commonly named birthmarks and moles. Nevi are benign by definition...

    , or birthmark
  • Human variability
    Human variability
    Human variability, or human variation, is the range of possible values for any measurable characteristic, physical or mental, of human beings. Differences can be trivial or important, transient or permanent, voluntary or involuntary, congenital or acquired, genetic or environmental...

  • List of cutaneous conditions
  • List of Mendelian traits in humans

External links

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