What is Albinism

Albinism is a disease in which a person has partial or complete loss of pigmentation (coloring) of the skin, eyes and hair.
Albinism is a genetic condition resulting in a lack of pigmentation in the eyes, skin and hair. It is an inherited condition arising from the combination of recessive genes passed from both parents of an individual. A variety of problems with photosensitivity in eyesight and skin usually result from the condition. This article is intended to cover mainly human albinism, although many of the features mentioned would probably also apply to albinism in animals.

Classification=
There are two main types of albinism: oculocutaneous albinism (OCA), where melanin pigment is missing in the skin, hair and eyes, and ocular albinism (OA), where the melanin pigment is mainly missing from the eyes, while the skin and hair appear normal. OCA is more common than OA.

1 Lack of Pigmentation=
The gene which results in albinism prevents the body from making the usual amounts of a pigment called melanin.

There are many genes which are now scientifically proven to be associated with albinism (or better: alterations of the genes). All alterations, however, lead to an alteration of the melanin (pigment / colouring) production in the body. Melanin helps protect the skin from ultraviolet light coming from the Sun (see human skin color for more information). People with albinism lack this protective pigment in their skin, and can burn easily from exposure to the sun as a result. Lack of melanin in the eye often results in problems with vision, as the eye will not develop properly without the pigment.

Individuals with full albinism (called albinos) generally have flax-white hair, blue eyes and pale pink skin which makes them stand out. Sometimes hair pigmentation is not completely absent (white) but shows a pale or medium blonde. Often the affected persons are paler in complexion as the rest of the family. The myth that all persons with albinism have "white hair and red eyes" is NOT true. Colorless iris in humans is pale blue, not pink like in some animals, and the human eye is too deep for the pupil to appear red rather than black.

Growth and development of children with albinism should be (and is) normal however, as should their general health, life span, intelligence, and ability to have children. The chance of albino children resulting from the marriage of an albino with a non-albino is very low and is discussed below.

What causes it?
Genetic mutations that affect the production of a pigment called melanin. There is a cell called the melanocyte that is responsible for giving skin, hair, and eyes pigmentation.

In albinism, the melanocytes are present, but genetic mutations interfere with their pigment production or their ability to distribute it to keratinocytes, the major cell type comprising the epidermis, or outer layer of the skin. There are currently five known genetic types of albinism, the most common being oculocutaneous type 1 (OCA1) and type 2 (OCA2). Oculocutaneous means affecting the eyes and skin ("oculo" meaning eye and "cutaneous" meaning skin).

Patients with OCA1 have mutations in a gene called TYR that is responsible for creating the enzyme tyrosinase, used by cells to convert the amino acid tyrosine into pigment molecules that color the skin, hair, and eyes. OCA2, the most common form of albinism in Africa, results from a mutation in the OCA2 gene, which encodes the P protein. We don't know what this P protein does.

What does a person with albinism look like?
Most people with OCA1 have snow-white skin, snow-white hair, and no pigment in their eyes. The iris (colored part of the eye that encircles the pupil) is a pale bluish pinkish color, while the pupil may actually be red. This redness comes from light entering the pupil and reflecting off of blood vessels in the retina, the light-sensitive layer of tissue lining the back of the eyeball. Normally, the pupil appears black because pigment molecules in the retina absorb light entering the eye, preventing it from bouncing back to the outside world.
Those with OCA2 can make a small amount of pigment and thus may have light blond to brown hair color. Their irises are blue to light gray and their pupils dark red to light gray.

What are some other conditions associated with albinism?
Without pigment in the skin, you are more susceptible to non-melanoma skin cancers in keratinocytes. Normally, melanocytes distribute pigment molecules to keratinocytes, where they act sort of like umbrellas shielding the nucleus (and the DNA inside) from the sun's UV radiation. Albinos are particularly at risk for squamous cell carcinoma, a cancer of the outermost layer of skin, and basal cell carcinoma affecting deeper layers. They also may experience premature skin aging. Melanin helps prevents wrinkles and elastosis (breakdown of elasticity) by blocking UV radiation.

How does this lack of pigment in the eyes affect vision?
People with albinism are legally blind because photoreceptors (cells in the retina that detect light) get oversaturated with light and send confusing messages to the brain. If you look at a person with albinism, you'll see a nystagmus, or fluttering, in their eyes; the eyes are sort of bouncing in their sockets because they are getting a confusing visual stimulus.

 Visual Problems Associated with Albinism=

People with albinism generally suffer impaired vision. They may have varying degrees of partial-sightedness ; either near-sighted or far-sighted. Most albinos suffer nystagmus or stigmatism (a rapid, involuntary "shaking" of the eyes), though this and general vision often improves towards middle-age, when most "normally" sighted individuals begin to suffer long- or short-sightedness, due to changes in muscle tension.

Individuals with these conditions may be helped by the use of glasses and low-visual aids such as magnifiers, as well as bright but angled reading lights, but their vision cannot be corrected completely. Although surgery is possible on the ocular muscles, effectively simulating (to a limited degree) the improvements in the albino's vision that often come with age, the gain is generally thought out-weighed by the trauma.

The lack of pigment in the eye generally leads to ocular photophobia or hyper- photo-sensitivity . This is due not so much to the iris allowing stray light to enter the eye, as to a lack of pigment within the eye, allowing light to refract within the eyeball. A good analogy would be taking a picture with a film camera that is painted white within, rather than black. Such sensitivity generally leads to a dislike of bright lights, but does not prevent people with albinism enjoying the outdoors. They should avoid prolonged exposure to bright sunlight, as their skin is particularly susceptible to sunburnA sunburn is a radiation burn to the skin produced usually by overexposure to the ultraviolet (UV) radiation from the sun. A similar burn can be produced by overexposure to other sources of UV, such as tanning lamps and welding arcs. Exposure of the skin.

Genetics

In Ocular-cutaneous Albinism, individuals inherit an "albinism geneDNA and to a chromosome (right). Introns are regions often found in eukaryote genes which are removed in the splicing process: only the exons encode the protein. This diagram labels a region of only 40 or so bases as a gene. In reality many genes are much" from both parents. Where an individual receives one albinism gene and one normal gene, that person will not show outward signs of the condition, but will become a carrierCarrier has several different meanings: in telecommunication, a carrier wave in biology, an asymptomatic carrier the Carrier tribe a First Nations tribe living in British Columbia, Canada a common carrier a transport business ( shipping or telecom) an air of the recessive gene. Where two carriers of the recessive gene have a child together, that child will have a one in four chance of receiving two albinism genes, and having albinism. The child will have one in four chances of getting neither albinism gene, having normal pigment, and not being a carrier. The child has two in four chances of getting one normal and one albinism gene, having normal pigment but being a carrier.

Are there any treatments for albinism?
No, there are not. Patients with albinism are advised to protect themselves from the sun.