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DianeHaught
Post subject: What is Albinism?  PostPosted: Jan 07, 2006 - 06:41 AM





Sergeant
What is Albinism?



The word "albinism" refers to a group of inherited conditions. People with albinism have little or no pigment in their eyes, skin, or hair. They have inherited genes that do not make the usual amounts of a pigment called melanin.

One person in 17,000 in the U.S.A. has some type of albinism. Albinism affects people from all races. Most children with albinism are born to parents who have normal hair and eye color for their ethnic backgrounds. Often people do not recognize that they have albinism.

A common myth is that by definition people with albinism have red eyes. In fact there are different types of albinism, and the amount of pigment in the eyes varies. Although some individuals with albinism have reddish or violet eyes, most have blue eyes. Some have hazel or brown eyes.

Vision Problems

People with albinism always have problems with vision, and many have low vision. Many are "legally blind," but most use their vision for reading, and do not use braille. Some have vision good enough to drive a car.

Vision problems in albinism result from abnormal development of the retina and abnormal patterns of nerve connections between the eye and the brain. It is the presence of these eye problems that defines the diagnosis of albinism. Therefore the main test for albinism is simply an eye exam.

Types of Albinism

While most people with albinism have very light skin and hair, not all do. Oculocutaneous (pronounced Ock-you-low-kew-Tain-ee-us) albinism involves the eyes, hair, and skin. Ocular albinism involves primarily the eyes, while skin and hair may appear similar or slightly lighter than that of other family members.

Over the years researchers have used various systems for classifying oculocutaneous albinism. In general, these systems contrasted types of albinism having almost no pigmentation with types having slight pigmentation. In less pigmented types of albinism, hair and skin are cream-colored, and vision is often in the range of 20/200. In types with slight pigmentation, hair appears more yellow or red-tinged, and vision often corrects to 20/60. Early descriptions of albinism called these main categories of albinism "complete" and "incomplete" albinism. Later researchers used a test that involved plucking a hair root, and seeing if it would make pigment in a test tube. This test separated "ty-neg" (no pigment) from "ty-pos" (some pigment). Further research showed that this test was inconsistent, and added little information to the clinical exam.

Recent research has used analysis of DNA, the chemical which encodes genetic information, to arrive at a more firm classification system for albinism. Type 1 albinism (also called tyrosinase-related albinism) is the type involving almost no pigmentation. Type 1 albinism results from a genetic defect in an enzyme called tyrosinase. This enzyme helps the body to change the amino acid tyrosine into pigment. (An amino acid is a "building block" of protein, and comes from protein in the diet.) Type 2, a type with slight pigmentation, results from a defect in a different gene called the "P" gene.
Researchers have identified several other genes that cause forms of albinism. In one form of albinism, the Hermansky-Pudlak syndrome, there can be problems with bleeding, and with lung and bowel disease as well. Hermansky-Pudlak syndrome is a less common form of albinism, but should be suspected if a child with albinism shows unusual bruising or bleeding.

Genetics of Albinism

For nearly all types of albinism both parents must carry an albinism gene to have a child with albinism. Because the body has two sets of genes,a person may have normal pigmentation but carry the albinism gene. If a person has one gene for normal pigmentation and one gene for albinism, he or she will have enough genetic information to make normal pigment. The albinism gene is "recessive" it does not result in albinism unless a person has two copies of the gene for albinism and no copy of the gene that makes normal pigment.

When both parents carry the gene, and neither parent has albinism, there is a one in four chance at each pregnancy that the baby will be born with albinism. This type of inheritance is called autosomal recessive inheritance.


(The most common type of ocular albinism follows a different pattern of inheritance. The NOAH Information Bulletin "Ocular Albinism" has more information.)

Each parent of a child with oculocutaneous albinism must carry the gene. Both the father and the mother must carry the gene for albinism. For couples who have not had a child with albinism, there is no simple test to determine whether a person carries a gene for albinism. Researchers have analyzed DNA of people with albinism and found the changes that cause albinism, but these changes are not always in exactly the same place, even for a given type of albinism. Therefore the tests for the gene may be inconclusive.

If parents have had a child with albinism previously, there is a way to test in subsequent pregnancies to see if the fetus has albinism. The test uses amniocentesis (placing a needle into the uterus to draw off fluid). Cells in the fluid are examined to see if they have an albinism gene from each parent.

For specific information and genetics and testing, seek the advice of a qualified genetic counselor. Genetic counselors are usually associated with universities and children's hospitals. The National Society of Genetic Counselors at (610) 872-7608 in Philadelphia maintains a referral list.

Those considering prenatal testing should be made aware that people with albinism can adapt well to their disabilities, and lead fulfilling lives.

Vision Rehabilitation: Eye conditions common in albinism include

Nystagmus, irregular rapid movement of the eyes back and forth.
Strabismus, muscle imbalance of the eyes ("crossed eyes" or "lazy eye")
Sensitivity to bright light and glare.
People with albinism may be either far-sighted or near-sighted, and often have astigmatism (distortion of a viewed image).
These eye problems result from abnormal development of the eye because of lack of pigment. The retina, the surface inside the eye that receives light, does not develop normally before birth and in infancy. The nerve signals from the retina to the brain do not follow the usual nerve routes. The iris, the colored area in the center of the eye, does not have enough pigment to screen out stray light coming into the eye. (Light normally enters the eye only through the pupil, the dark opening in the center of the iris, but in albinism light can pass through the iris as well.)

For the most part, treatment of the eye conditions consists of visual rehabilitation. Surgery to correct strabismus may improve the appearance of the eyes. However, since surgery will not correct the misrouting of nerves from the eyes to the brain, surgery will not provide fine binocular vision. In the case of esotropia or "crossed eyes," surgery may help vision by expanding the visual field (the area that the eyes can see while looking at one point).

People with albinism are sensitive to glare, but they do not prefer to be in the dark, and need light to see just like anyone else. Sunglasses or tinted contact lenses help outdoors. Indoors, it is important to place lights for reading or close work over a shoulder rather than in front.

Various optical aids are helpful to people with albinism, and the choice of an optical aid depends on how a person uses his or her eyes in jobs, hobbies, or other usual activities. Some people do well using bifocals which have a strong reading lens, prescription reading glasses, or contact lenses. Others use hand-held magnifiers or special small telescopes. Some use bioptics, glasses which have small telescopes mounted on, in, or behind their regular lenses, so that one can look through either the regular lens or the telescope. Newer designs of bioptics use smaller light-weight lenses. Some states allow the use of bioptic telescopes for driving. (See also NOAH bulletin "Low Vision Aids.)

Optometrists or ophthalmologists who are experienced in working with low vision patients can recommend various optical aids. Clinics should provide aids on trial loan, and provide instruction in their use. The American Foundation for the Blind (1-800-AFB-LIND) maintains a directory of low vision clinics.

Medical Problems

In the United States, people with albinism live normal life spans and have the same types of general medical problems as the rest of the population. The lives of people with Hernansky-Pudlak syndrome can be shortened by lung disease or other problems. In tropical countries, those who do not use skin protection may develop life-threatening skin cancers. If they use appropriate skin protection, such as sunscreen lotions rated 20 or higher, and opaque clothing, people with albinism can enjoy outdoor activities even in summer.

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. Families and schools must make an effort not to exclude children with albinism from group activities.

Contact with others with albinism or who have albinism in their families is most helpful. NOAH can provide the names of contacts in many regions of the country.



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Other Resources
A chapter in a textbook available in most medical libraries: King RA, Hearing VJ, Creel DJ, Oetting WS: Albinism, 4353-4393, in Scrivner, Charles R. et al, The Metabolic and Molecular Bases of Inherited Disease, 7th ed., McGraw Hill Inc. Health Professions Division, New York 1995.

Technical updates on genetics are accessible via internet from Online Mendelian Inheritance in Man, address http://www3.ncbi.nlm.nih.gov/Omim/searchomim.html

NOAH publishes a large print twice-yearly newsletter, NOAH News, as well as many Information Bulletins about albinism. NOAH also maintains an Internet sitethat includes public bulletin boards for exchanging information about albinism. The organization sponsors national and regional conferences. Local chapters meet in many areas of the U.S. and Canada. NOAH can provide a list of chapters and contact persons. Founded in 1982 in Philadelphia, NOAH is an all-volunteer organization. NOAH's objectives are to provide information and support to individuals and families with albinism, to promote public and professional education about these conditions, and to encourage research and research funding that will lead to improved diagnosis and treatment. Contact NOAH for more information, or to join.

The Hermansky-Pudlak Network, One South Road, Oyster Bay, New York 11771-1905., phone 800-789-9HPS, a NOAH affiliate, provides information and support to individuals and families with HPS.

American Foundation for the Blind, 11 Penn Plaza, Suite 300, New York, NY 10001, phone 800-AFB-LIND, provides information about programs and clinics for people with impaired vision throughout the United States.

National Organization for Albinism and Hypopigmentation, PO Box 959, East Hampstead, NH 03826-0959, phone 800 473-2310, Phone: 603 887-2310.



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Funding for the development and original printing of these Information Bulletins was provided by the Innovating Worthy Projects Foundation of Somers Point, New Jersey. NOAH gratefully acknowledges their assistance.




NOAH
The National Organization for Albinism and Hypopigmentation
PO Box 959, East Hampstead, NH 03826-0959
Phone: 800 473-2310 (US and Canada) Phone: 603 887-2310 Fax: 800-648-2310
http://www.albinism.org

If you have any questions or comments, please e-mail us at webmaster@albinism.org

NOAH is a volunteer organization for persons and families involved with the condition of albinism. It does not diagnose, treat, or provide genetic counseling. It is involved in self-help, while trying to promote research and education.



Medical Information
It is not the intention of Raptor-Pack to provide specific medical advice but rather to provide users with information to better understand their health and their diagnosed disorders. Specific medical advice will not be provided, and Raptor-Pack urges you to consult with a qualified physician for diagnosis and for answers to your personal questions and specific medical advice


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Hug

Diane



"I'd rather regret something I did, than regret never doing it at all"
 
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