Albinism

Photo by: Natalia_R

Definition

Albinism is an inherited condition that is present at birth. It is characterized by a lack of melanin, the pigment that normally gives color to the skin, hair, and eyes. Many types of albinism exist, all of which involve lack of pigment in varying degrees. The condition, which is found in all races, may be accompanied by eye problems and may ultimately lead to skin cancer .

Description

The most common type of albinism is oculocutaneous albinism, which affects the eyes, hair, and skin. In its most severe form, hair and skin remain completely white throughout life. People with a less severe form are born with white hair and skin that turn slightly darker as they age. Everyone with oculocutaneous albinism experiences abnormal flickering eye movements ( nystagmus ) and sensitivity to bright light. There may be other eye problems as well, including poor vision and crossed or "lazy" eyes ( strabismus ).

The second most common type of the condition is known as ocular albinism, in which only the eyes lack color; skin and hair are normal. Some types of ocular albinism cause more problems, especially eye problems, than others.

Albinism is also referred to as hypopigmentation.

Demographics

Albinism is a rare disorder found in fewer than five people per 100,000 in the United States and Europe. Although albinism can affect all races, other parts of the world have a much higher rate; for example, albinism is found in about 20 out of every 100,000 people in southern Nigeria. The parents of most children with albinism have normal hair and eye color for their ethnic background and do not have a family history of albinism.

Causes and symptoms

Albinism is an inherited problem caused by an alteration in one or more of the genes that are responsible for directing the eyes and skin to produce or distribute melanin, which is a photoprotective pigment that absorbs ultraviolet (UV) light coming from the sun so that the skin is not damaged. Sun exposure normally produces a tan, which is an increase in melanin pigment in the skin. Many people with albinism do not have melanin pigment in their skin, do not tan with exposure to the sun, and as a result develop sunburn . Over time, people with albinism may develop skin cancers if they do not adequately protect their skin from sun exposure.

Melanin is also important in the eyes and brain, but it is not known what role melanin plays in those areas. Parts of the retina do not develop correctly if melanin pigment is not present during development. Also nerve connections between the retina and brain are altered if melanin is not present in the retina during development.

Albinism is a autosomal recessive disease, which means that a person must have two copies of the defective gene to exhibit symptoms of the disease. The child therefore inherits one defective gene responsible for making melanin from each parents. Because the task of making melanin is complex, there are many different types of albinism, involving a number of different genes.

It is also possible to inherit one normal gene and one albinism gene. In this case, the one normal gene provides enough information to make some pigment, and the child has normal skin and eye color. The child has one gene for albinism. About one in 70 people are albinism carriers, with one defective gene but no symptoms; they have a 50 percent chance of passing the albinism gene to their child. However, if both parents are carriers with one defective gene each, they have a one in four chance of passing on both copies of the defective gene to the child, who will have albinism. There is also a type of ocular albinism that is carried on the X chromosome and occurs almost exclusively in males because they have only one X chromosome and, therefore, no other gene for the trait to override the defective one.

People with albinism may experience a variety of eye problems, including one or more of the following:

They may be very far-sighted or near-sighted and may have other defects in the curvature of the lens of the eye (astigmatism) that cause images to appear unfocused.
They may have a constant, involuntary movement of the eyeball called nystagmus.
They may have problems in coordinating the eyes in fixing and tracking objects (strabismus), which may lead to an appearance of having "crossed eyes" at times.
They may have reduced depth perception due to altered nerve connections from the retina to the brain.
Their eyes may be very sensitive to light (photophobia) because their irises allow stray light to enter their eyes. It is a common misconception that people with albinism should not go outside on sunny days, but wearing sunglasses can make it possible to go outside quite comfortably.

One of the myths about albinism is that it causes people to have pink or red eyes. In fact, people with

African child with albinism surrounded by normally pigmented friends.

albinism can have irises varying from light gray or blue to brown. (The iris is the colored portion of the eye that controls the size of the pupil, the opening that lets light into the eye.) If people with albinism seem to have reddish eyes, it is because light is being reflected from the back of the eye (retina) in much the same way as happens when people are photographed with an electronic flash. In addition, albinism does not cause blindness.

In addition to characteristically light skin and eye problems, people with a rare form of albinism called Hermansky-Pudlak syndrome (HPS) also have a greater tendency to have bleeding disorders, inflammation of the large bowel (colitis), lung (pulmonary) disease, and kidney (renal) problems.

When to call the doctor

The doctor should be called when a person with albinism exhibits symptoms such as photophobia that cause discomfort. Also the doctor should be consulted if there are any skin changes that might be an early sign of skin cancer.

The parent of a child with albinism should also call the doctor if the child bruises easily or has unusual bleeding, such as repeated nosebleeds or bloody diarrhea . The child may have the rare Hermansky-Pudlak syndrome, which requires additional medical care.

Diagnosis

It is not always easy to diagnose the exact type of albinism a person has. The specific type is sometimes determined by developing a thorough family history and by examining the patient and several close relatives. In the early 2000s, a blood test has been developed that can identify carriers of the gene for some types of albinism; a similar test during amniocentesis can diagnose some types of albinism in an unborn child. A chorionic villus sampling test during the fifth week of pregnancy may also reveal some types of albinism.

There are also two tests available that can identify two types of the condition. The hairbulb pigmentation test is used to identify carriers by incubating a piece of the person's hair in a solution of tyrosine, a substance in food which the body uses to make melanin. If the hair turns dark, it means the hair is making melanin (a positive test); light hair means there is no melanin. This test is the source of the names of two types of albinism: "typos" and "ty-neg."

The tyrosinase test is more precise than the hair-bulb pigmentation test. It measures the rate at which hair converts the amino acid tyrosine into another chemical (3,4-dihydroxyphenylalanine, or DOPA), which is then made into pigment. The hair converts tyrosine with the help of an enzyme called tyrosinase. In some types of albinism, a genetic defect in tyrosinase means that the amino acid tyrosine cannot be converted by tyrosinase into melanin.

Treatment

There is no treatment that can replace the lack of melanin that causes the symptoms of albinism. In addition, doctors can only treat, but not cure, the eye problems that often accompany the lack of skin color. Glasses or corrective lenses and low vision aids, for example, magnifiers, monoculars (handheld telescopes used with only one eye), or bioptics (glasses with small telescopic lenses mounted in the standard lenses) can improve vision but usually cannot correct vision to 20/20. The lenses can be tinted to ease pain from too much sunlight. For reading, children with albinism may or may not need materials with large print text, depending on the severity of their vision problems. There is no cure for involuntary eye movements (nystagmus), and treatments for focusing problems (surgery or contact lenses ) are not effective in all cases.

Crossed eyes (strabismus) can be treated during infancy by using eye patches, surgery, or medicine injections. Treatment may improve the appearance of the eye, but it can do nothing to cure the underlying condition.

KEY TERMS

Amino acid —An organic compound composed of both an amino group and an acidic carboxyl group. Amino acids are the basic building blocks of proteins. There are 20 types of amino acids (eight are "essential amino acids" which the body cannot make and must therefore be obtained from food).

Astigmatism —An eye condition in which the cornea doesn't focus light properly on the retina, resulting in a blurred image.

Carrier —A person who possesses a gene for an abnormal trait without showing signs of the disorder. The person may pass the abnormal gene on to offspring. Also refers to a person who has a particular disease agent present within his/her body, and can pass this agent on to others, but who displays no symptoms of infection.

DNA —Deoxyribonucleic acid; the genetic material in cells that holds the inherited instructions for growth, development, and cellular functioning.

DOPA —The common name for a natural chemical (3,4-dihydroxyphenylalanine) made by the body during the process of making melanin.

Enzyme —A protein that catalyzes a biochemical reaction without changing its own structure or function.

Gene —A building block of inheritance, which contains the instructions for the production of a particular protein, and is made up of a molecular sequence found on a section of DNA. Each gene is found on a precise location on a chromosome.

Hairbulb —The root of a strand of hair from which growth and coloration of the hair develops.

Hermansky-Pudlak syndrome —A rare type of albinism, most common in the Puerto Rican community, which can cause pigment changes, lung disease, intestinal disorders, and blood disorders.

Melanin —A pigment that creates hair, skin, and eye color. Melanin also protects the body by absorbing ultraviolet light.

Nystagmus —An involuntary, rhythmic movement of the eyes.

Strabismus —A disorder in which the eyes do not point in the same direction. Also called squint.

Tyrosinase —An enzyme in a pigment cell which helps change tyrosine to dopa during the process of making melanin.

Tyrosine —An amino acid synthesized by the body from the essential amino acid phenylalanine. It is used by the body to make melanin and several hormones, including epinephrine and thyroxin.

Patients with albinism should avoid excessive exposure to the sun, especially between 10 a.m. and 2 p.m., and should wear long sleeves and pants if possible. If exposure cannot be avoided, they should use a UVAUVB sunblock with an SPF rating at least 30.

Most children with albinism function satisfactorily in a mainstream classroom as long as the school provides classroom assistance for their vision needs. The child's eye doctor, the classroom teacher, and the school's vision resource teacher should work as a team with the parents to determine what classroom modifications and vision aids will best help the child. The local school district or the state agency for the blind should be contacted during the child's infancy or during preschool years to determine what assistive services might be available for the child. Early intervention allows parents and teachers to develop an educational plan for the child.

Prognosis

In the United States, people with this condition can expect to have a normal lifespan. However, one of the greatest health hazards for people with albinism is excessive exposure to sun without protection, which may lead to skin cancer. Wearing opaque clothes and sunscreen with at least an SPF rating of 30, people with albinism can safely work and play outdoors even during the summer.

Prevention

Genetic counseling should be considered for individuals with a family history of albinism.

Parental concerns

Children with albinism may experience complex social problems because of their unusual appearance, especially when a member of a normally dark-skinned ethnic group has albinism. The eyes of children with albinism may move rapidly and not focus together, and the children may have to squint, tilt their heads, and hold reading materials close in order to see. These behaviors may result in the child being treated badly by peers. Modifications made for the children in the classroom and in physical education classes to compensate for low vision may make them feel even more isolated. Parents often feel that teasing and name-calling, insensitivity, and ignorance are the greatest challenges that they face with regards to their child's albinism. The support and love of these families of children with albinism are essential to helping the children understand and accept themselves. Support groups for the children and for their families, as well as counseling, may be useful for developing means of coping with the social effects of albinism.

Resources

BOOKS

Albinism: A Medical Dictionary, Bibliography, and Annotated Research Guide to Internet References. San Diego, CA: Icon Health Publications, 2003.

Edwards, Lee G. Too White to Be Black and Too Black to Be White: Living with Albinism. Bloomington, IN: AuthorHouse, 2001.

Mitchell, Elizabeth Tromsness. Albinism in the Family: Albinismo en la Familia. Bloomington, IN: AuthorHouse, 2004.

ORGANIZATIONS

Albinism World Alliance. Web site: http://www.albinism.org/awa.html.

American Foundation for the Blind. 11 Penn Plaza, Suite 300 New York, NY 10001. Web site: http://www.afb.org/.

Hermansky-Pudlak Syndrome Network Inc. One South Road, Oyster Bay, NY 11771–1905. Web site: http://www.hpsnetwork.org/HTML/frame.html.

National Organization for Albinism and Hypopigmentation (NOAH). PO Box 959, East Hampstead, NH 03826–0959. Web site: http://www.albinism.org.

WEB SITES

King, Richard A., et al. "Facts about Albinism." International Albinism Center, University of Minnesota. Available online at http://www.cbc.umn.edu/iac/facts.htm (accessed November 8, 2004).

Judith L. Sims Carol A. Turkington