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Albinism (from ), more technically '''hypomelanism''' or '''hypomelanosis''', is a form of Hypopigmentary Congenital Disorder , characterized by a lack of Melanin Pigment in the eyes, skin and hair (or more rarely the eyes alone). Albinism results from inheritance of Recessive Gene s. The condition is known to affect mammals, fish, birds, reptiles, and amphibians. While the most common term for an organism affected by albinism is "albino" (noun and adjective), the word is sometimes used in a derogatory way towards people; more neutral terms are "albinistic" (adjective) and "person with albinism" (noun). Additional clinical adjectives sometimes used to refer to animals are "albinoid" and "albinic". CAUSES Albinism is a (see also Mendelian Inheritance In Man for more information about this source). Albinism used to be categorized as Tyrosinase -positive or -negative. In cases of tyrosinase-positive albinism, the Enzyme tyrosinase is present. The Melanocyte 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. "Facts about Albinism" , by Richard King ''et al''. The chance of offspring with albinism resulting from the pairing of an organism with albinism and one without albinism is low, as discussed in more detail below. 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, because it is passed on to offspring through X-linked inheritance. Thus, males more frequently have ocular albinism. "Facts about Albinism" , by Richard King ''et al''. Because organisms with albinism have skin that lacks (sufficiently or entirely) the dark pigment melanin, which helps protect the skin from Ultraviolet Radiation coming from the sun, they can Sunburn easily from overexposure. (See Human Skin Color for more information). Lack of melanin in the eye also results in problems with vision, related and unrelated to Photosensitivity , which are discussed further below. Most organisms 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 , in which Xanthophore Metabolism , instead of Synthesis of melanin, is affected, resuling in reduction or absence of red and yellow pteridine pigments. "Amphibian Biology & Physiology: ''Caudata''" at ''Amphibian Information Resource: An Educational Web Project About Amphibian Species''; sourced December 2006, actual authoring/publication date unspecified. Of all these conditions, only albinism and melanism affect humans. , a strain commonly used for both Biomedical And Basic Research. ]] 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. Ilo Hiler, Albinos. ''Young Naturalist''. The Louise Lindsey Merrick Texas Environment Series, No. 6, pp. 28-31. Texas A&M University Press, College Station (1983) S. Dobosz, K. Kohlmann, K. Goryczko, H. Kuzminski (2000) Growth and vitality in yellow forms of rainbow trout. ''Journal of Applied Ichthyology.'' 16, 117–120. However the novelty of albino animals has occasionally led to their protection by groups such as the Albino Squirrel Preservation Society . Intentionally-bred albinistic strains of some animal species are commonly used as Model Organism s in biomedical study and experimentation. Examples include the BALB/c mouse and Wistar and Sprague Dawley Rat strains, while albino rabbits were historically used for Draize Toxicity Testing . Draize, J.H., Woodard, G. & Calvery, H.O. (1944) Methods for the study of irritation and toxicity of substances applied topically to the skin and mucous membranes. ''J. Pharmacol. and Exp. Therapeutics.'' 82, 377–390. Albino Axolotl s, Zebrafish , Medaka and Frogs are other common laboratory animals. The incidence of albinism can be artificially increased in fish by exposing the eggs to Heavy Metals .1 TYPES OF HUMAN ALBINISM About 1 in 17,000 human beings has some type of albinism, although up to 1 in 70 is a carrier of albinism genes. "Albinism" by Carol A. Turkington at answers.com There are two main categories of albinism in humans:
While there is only one major type of ocular albinism, there are several varieties of oculocutaneous albinism (and disorders which produce the same or similar results), some of which have subtypes. Some are easily distinguished by appearance, but in most cases, genetic testing is the only way to be certain. Oculocutaneous albinism family with probable OCA1a.]]
Ocular albinism family
The skin color of people affected by OA ''can'' be slightly lighter than those of the rest of their families. The eye color can vary greatly, and in some cases only examination of the Retina or genetic testing can reveal OA for certain. Some form of OA afflicts 1 in 50,000 people, though certain isolated populations are at greater risk. Other types Other rare variants of albinism are theorized (by ongoing research as of 2007) to exist, such as
SYMPTOMS AND CONDITIONS ASSOCIATED WITH ALBINISM Genetic Testing 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. Eye conditions common in albinism may or may not include:
]] Organisms with albinism usually have impaired vision due to one or more of the listed conditions. While a person with albinism may suffer from common refractive errors like nearsightedness or farsightedness, the visual problems particularly 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 e), which results in eccentric fixation and lower visual acuity, and often a minor level of strabismus. Nystagmus is usually seen, as is Photophobia or light sensitivity (see below). The Iris is a Sphincter with pigmented tissue (which makes up the color of the eyes) that contracts to limit the amount of light that can enter through the pupil and relaxes again to allow for better vision in darkness. This mechanism can be observed in humans and mammals (like in cat's eyes) and is needed because too much light is uncomfortable or even painful and decreases vision. In people with albinism, the iris does not have enough pigment to block the light, thus the decrease of pupil diameter is only partially successful in reducing the amount of light that enters 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. "Albinism - Review of Optometry Online" The resulting sensitivity (photophobia) generally leads to a dislike of and discomfort in bright light, but does not prevent people with albinism enjoying the outdoors, especially when using sunglasses and/or brimmed hats. "Facts about Albinism" , by Dr. Richard King et al. The lack of pigment also makes the skin unusually sensitive to sunlight and thus susceptible to Sunburn , so people with albinism should either avoid prolonged exposure to bright sunlight or protect their skin. TREATMENT OF THE SYMPTOMS Albinism is a condition that cannot be "cured" or "treated" per se, 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. Surgical treatment For the most part, treatment of the eye conditions consists of visual rehabilitation. Surgery is possible on the ocular muscles to decrease (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). Vision aids , 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 bulletin "Low Vision Aids".) Although still disputed among the experts, many Ophthalmologists recommend the use of glasses from early childhood onward to allow the eyes the best development possible. Optometrists or ophthalmologists who are experienced in working with Low Vision patients can recommend various optical aids. Clinics may provide these aids on trial loan, and provide instruction in their use. 3 maintains a directory of low vision clinics. Sun protection , with Melanoma s.]] It is vital that people with albinism use sunscreen when exposed to sunlight to prevent premature skin aging or Skin Cancer . This poses a problem for those who cannot afford Sunscreen , especially in regions with high exposure to sunlight, as in Africa. Special Sun Protective Clothing and swimsuits are available and are a good alternative to excessive use of sunscreen. Use of Sunglasses and hats with wide brims can make the glare outside bearable. Other things that can help people with albinism are avoiding sudden changes of the lighting situation (switching the light on in complete darkness), using dimmable switches and adding tint to car windows or blinds to normal windows. Lights should be yellowish rather than blue and not point towards the usual position of a person with albinism (like their seat at a table). When possible, people with albinism generally prefer to have the light on their backs rather than face it. MISCONCEPTIONS While some of the very rare albinism disorders that are coupled with deafness and immunodeficiency appear to be linked with inbreeding, the vast majority of sufferers of common albinism are not the product of such unions; the more usual albinism genes are widespread enough that they can easily produce albinistic offspring from parents that are not related. A common misconception is that albinistic individuals of a species are sterile; they are in fact fully capable of reproducing. It is also thought by many that people with albinism live short life spans. This is not true in general, but may be a distorted view of a more reasonable fact that people with albinism have a higher risk of skin cancer if they do not use proper skin protection when in the sun. (Some very rare variants of albinism are lethal in and of themselves by adulthood or sooner, but they are so little-known by the general public that they are unlikely to have contributed to this belief.) CULTURE albino pride parade during Bahia carnival]] See Also: Albinism in popular culture While on the physical side, humans with albinism commonly have vision problems and need sun protection, they also face a social challenge, as the condition is often a source of ridicule, discrimination or even fear. Due to albinism's effect on one's outward appearance, cultures around the world have developed many superstitions regarding people with albinism, who are believed by some to have , people with albinism were historically degraded, and regarded as " Curse d". A long-standing American Urban Legend is that of alleged "albino colonies" in rural New Jersey . Portrayals of people with albinism in Literature and Film s are rarely positive. This fact is sometimes referred to as the ''"evil albino" stereotype'', or ''albino bias''. While this stereotype is common, in recent years a few more positive roles have also been cast for mock-albino actors and occasionally genuinely albinistic ones. A number of real people with albinism have become famous, including historical figures such as King Edward The Confessor of England, Emperor Seinei of Japan, and Oxford don William Archibald Spooner ; musicians such as Johnny and Edgar Winter , Winston "King Yellowman" Foster , Brother Ali , and Willie "Piano Red" Perryman ; even a fashion model, Connie Chiu . There have also been some well-known albino animals, including Migaloo (an Australian whale), Copito De Nieve (a Barcelona Zoo gorilla), and Snowdrop (a Bristol Zoo penguin). SEE ALSO
REFERENCES EXTERNAL LINKS Albinism in humans Albinism support organizations
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Albinism in animals
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