Albinism

Olivia Wolf - A3

Alternative Names

Oculocutaneous albinism; Ocular albinism; Hermansky-Pudlak syndrome (Haldeman-Englert 28).

Cause of the Disorder

Oculocutaneous albinism (OCA) is caused by a mutation in one of four genes. (Newman 21-22). These mutations interfere with the enzyme tyrosinase (tyrosine 3-monooxygenase) which synthesizes melanin from the amino acid tyrosine. This can cause melanin production to be slowed or completely stopped (Ogunsi 4).


Chromosome Number

In X-linked inheritance, X chromosome is the one that holds the gene for albinism. Since females have two X chromosomes and males only have one, X-linked ocular albinism appears almost solely in males (Newman 25).


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Albino Family

Prenatal Tests

Yes, there are prenatal tests available for diagnosing the disease of Albinism early. At first tests consisted of histologic and electron microscopic examination of fetal skin biopsies, but recently they have changed the test to a molecular genetic approach which has become available because scientists identified two mutated copies of the TYR gene - tyrosinase (Hadassah 1).


Symptoms

Symptoms include: Absence of color in the hair, skin, or iris of the eye, Lighter than normal skin and hair, Patchy, and missing skin color. Symptoms associated with Albinism include: Crossed eyes (strabismus), Light sensitivity (photophobia), Rapid eye movements (nystagmus), Vision problems, or functional blindness (Haldeman-Englert 10-11).

Number of People Affected

Albinism affects roughly 1 in 17,000 people globally. In sub-Saharan Africa, the rate of albinism is around 1 in 5,000; however, in Europe and America, it is closer to 1 in 20,000 (Newman 2-3).


Candidate for the Disorder

Albinism is most commonly found in males because the mutation is found on the X chromosome and it is popular among Africans, occurring in 1 in every 5,000 people (Newman 2, 25).

Inheritance and Reproduction

In X-linked recessive Albinism, the genetic defect is located on the "X" chromosome and usually affects males only. This happens because females have two X chromosomes. Females with one normal X chromosome and one mutated X chromosome generally do not have Albinism; however, these females are at risk for passing on genetic disease. These females are called "carriers". On the other hand, since a male only has one X chromosome, if it is mutated he has no normal copy of the X chromosome and will have Albinism (Boles and Mason 21).


If a female carrier has children, there is a 50/50 chance that she will pass on the disease to her children. If that child happens to be a girl and inherits the gene, she will also become a carrier; however f the child is a boy and inherits the defective gene, he will develop the disease. On the other hand, if the female has has the disease and is not a carrier she will have it but it will be mild, usually. If she then decides to have children a boy will have the disease. In rare situations the disease in boys is so severe as to be lethal before birth, such that only girls are noted to be affected. However, in all cases of X-linked disease, boys and girls are always affected differently, with boys more severely affected than girls (Boles and Mason 22-23).

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Example of X-Linked Recessive Inheritance

Prevention

Since Albinism is inherited from the X chromosome there is no way to keep you from inheriting it. If you are a carrier or have the disease they only way it can be prevented from passing on to others is to not produce any offspring (Haldeman-Englert 23).

Treatment and Cures (Present and Future)

Sadly, there is no cure for Albinism. People that have Albinism only treat symptoms. Treatment for the disease may include: sunglasses to protect the eyes from UV rays, protective clothing and sunscreen to shelter the skin from ultraviolet rays, prescription eyeglasses to correct vision problems, and surgery on the muscles of the eyes to correct abnormal eye movements. Nitisinone may soon be a potential treatment for people with ocular albinism (Kivi and Solan 21).

Medical Assistance

Young children may need glasses, while older children may require bifocals. Occasionally, telescopic lenses mounted on glasses (bioptics) are prescribed for close-up work and distance vision since people with the disease commonly have eyesight problems. Tinted glasses may be used to reduce photophobia; however, simply wearing protecting clothing like sunglasses, hats, and long sleeves/pants outdoors to protect the fair skin. Nitisinone, is used for treating hereditary tyrosinemia type 1, elevates plasma tyrosine levels and increases eye and hair pigmentation (Bashour 2-4).

Long-Term Outlooks

Most forms of Albinism do not affect a lifespan; however, people with albinism may have to limit their outdoor activities because their skin and eyes are sensitive to the sun. Ultraviolet rays from the sun can cause skin cancer and vision loss in some people with albinism (Kivi and Solan 22-23).


Current Research

Recently, researchers at Brown University found the protein that is necessary for the proper functioning of an ion channel on the melanosome organelle. Further investigation has shown that the ion channel is like a gate that lets electrically charged chloride molecules flow into and out of the melanosome. When the melanosome lacks OCA2 or contains OCA2 with an albinism-associated mutation, the chloride flow doesn’t occur and the melanosome fails to produce melanin. This discovery is leading to new ideas on how to treat and maybe one day cure the disease (Orenstein 4-5).

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