What is albinism?
Albinism (also called achromia, achromasia, or achromatosis) is a congenital disorder characterized by the complete or partial absence of pigment in the skin, hair and eyes due to absence or defect of tyrosinase, a copper-containing enzyme involved in the production of melanin. While an organism with complete absence of melanin is called an albino, an organism with only a diminished amount of melanin is described as albinoid.
Albinism affects people of all ethnic backgrounds; its frequency worldwide is estimated to be approximately one in 20,000. Prevalence of the different forms of albinism varies considerably by population, and is highest overall in people of sub-Saharan African descent. Most children with albinism are born to parents who have normal hair and eye colour for their ethnic backgrounds. Two parents with albinism, however, increases the probability that their children will be born with the condition.
In humans, there are two principal types of albinism; oculocutaneous, affecting the eyes, skin and hair, and ocular affecting only the eyes.
Most people with oculocutaenous albinism 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 entirely lacks the dark pigment melanin, which helps protect the skin from the sun’s ultraviolet radiation, their skin can burn more easily from overexposure.
Occulocutaenous albinism is generally the result of the biological inheritance of genetically recessive alleles (genes) 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 (including humans) 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 sexes. 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.
For some people, albinism affects only their eyes. A common myth is that people with albinism have red eyes. In fact there are different types of albinism and the amount of pigment in the eyes varies. The human eye normally produces enough pigment to color the iris blue, green or brown. However, there are cases in which the eyes of an albinistic person appear red, pink or purple, depending on the amount of pigment present, due to the red of retina being visible through the iris.
All forms of albinism are associated with vision problems. The degree of vision impairment varies with the different types of albinism and many people with albinism are “legally blind”, but most use their vision for many tasks, including reading, and do not use Braille. Some people with albinism have sufficient vision to drive a car.
Eye conditions common in albinism include:
- Nystagmus, irregular rapid movement of the eyes back and forth, or in circular motion.
- Astigmatism, irregular shaped cornea requiring additional cylindrical corrective lenses in spectacles.
- Amblyopia, decrease in acuity of one or both eyes due to poor transmission to the brain, often due to other conditions such as strabismus.
- Optic nerve hypoplasia, an underdevelopment of the optic nerve.
Except for eye problems, most people with albinism are just as healthy as anyone else. In tropical countries, those who do not use skin protection may develop life-threatening skin cancers.
Society and culture
People with albinism are at risk of isolation because the condition is often misunderstood. Social stigmatization can occur, especially within communities of color, where the race or paternity of a person with albinism may be questioned.
In African countries such as Tanzania and Burundi, there has been an unprecedented rise in witchcraft-related killings of albino people in recent years, because their body parts are used in potions sold by witchdoctors. Some locals believe albinos are ghosts that can’t die. Others think they were born into cursed families. Another harmful and false belief is that sex with an albinistic woman will cure a man of HIV. This has led, for example in Zimbabwe, to rapes (and subsequent HIV infection).
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 was reported from the courts, as part of a continuing problem. National Geographic estimates that in Tanzania a complete set of albino body parts is worth $75,000.
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