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The Seen and Unseen Consequences of Albinism

The pigment loss seen in albinism has consequences for the skin, but a less visible ramification of the condition is on vision itself.

Today I learned two things. First, that we apparently have an albino squirrel on our campus. Second, that seeing an albino squirrel before a test is good luck.

While I have seen photographic evidence of the former, I remain skeptical of the latter. I think it might just be a great marketing gimmick for the Albino Squirrel Preservation Society founded on the campus of the University of Texas at Austin. (I am not making this part up!)

Albinism affects all sorts of animals and is relatively common in birds, reptiles, and amphibians. It has even been seen in plants where it results in a partial or complete loss of chlorophyll. In humans, oculocutaneous albinism is not a single condition but rather a group of somewhat rare genetic disorders characterized by low or absent pigmentation in the eyes, skin and hair. There are seven known types in humans, all due to a variant in one of several genes involved in the production of melanin.

Melanin is the name given to a group of pigments that give our skin, hair, and eyes their colour. They absorb ultraviolet radiation and protect us against sun damage, and we have two main types of melanin: eumelanin, which is brown or black, and pheomelanin, which is yellow. The body can create these melanin pigments using basic building blocks but the many steps in this recipe require specific proteins. When a gene coding for one of these proteins is mutated, as in the case of albinism, melanin production is reduced. People with albinism typically have lower levels of eumelanin, the dark pigment, but may have normal levels of pheomelanin in their hair.

Worldwide, albinism affects one in 17,000 to 20,000 people, with numbers fluctuating depending on the population. A little-known fact of oculocutaneous albinism is that its most debilitating effect is often on vision. Many people with albinism have reduced vision, a sensitivity to light (called photophobia), involuntary scanning eye movements (known as nystagmus), and/or strabismus (commonly known as “cross eyes”). How does a drop in pigmentation in the eye affect vision? Because melanin plays a role in a very peculiar type of pilgrimage. When the human embryo develops, half of the nerve fibres from the left eye need to make their way to the right part of the brain and vice versa. When you look at the nerve bundles from the eyes to the brain as seen from above, they form an “X”, with one half from each eye going to each side of the brain. Many factors are needed to ensure that the nerves grow in this way in the womb, and one of these factors is melanin. So when melanin levels are abnormally low, some nerve fibres don’t get routed properly and the back of the eye, responsible for clear vision, can get misshapen. In fact, there is another type of albinism that does not affect the skin but only affects the eyes.

People who have albinism need to diligently protect their skin from the sun and it is recommended they have a skin examination once or twice a year as they are at an increased risk for skin cancer. Many people with the condition can also benefit from low-vision aids like enlarged print and lighted magnifying glasses provided through vision rehabilitation. And then, of course, there’s managing the stigma attached to their appearance, which can be mild in some countries but lethal in others. In parts of Africa, people with albinism are persecuted and can be killed because of the belief that some of their body parts have magical properties and can be used in rituals.

In the animal kingdom, albinism can rob creatures of their camouflage. Our little campus albino squirrel should be fine, though. Winter is coming.


Take-home message:
-Albinism is a genetic condition that is seen throughout the animal kingdom and that results in reduced pigmentation.
-In humans, albinism is caused by a mutation in a set of genes involved in the creation of a pigment called melanin
-Albinism can cause low vision because the melanin pigment is necessary to the development of the connection between the eyes and the brain


@CrackedScience

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