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Facts About Albimism

 
 
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Facts About Albinism
Index
Questions and Answers:
What is Albinism? What is melanin pigment? How does melanin form? What Are the Problems with Albinism? What Eye Problems Result from Albinism What Can be Done for the Eye Problems? What Can be Done to Help Children with Albinism in School? How Much Time Can a Person with Albinism Stay in the Sun? How Well Do Sunscreens Work for People with Albinism? How do we classify albinism? How do we classify Oculocutaneous albinism?
OCA1. Tyrosinase Related Oculocutaneous Albinism.
OCA1A OCA1B Autosomal recessive ocular albinism.
OCA2. P-Gene Related Oculocutaneous Albinism
Brown OCA
Prader-Willi and Angelman Syndrome. OCA3. TRP1-Related OCA Hermansky Pudlak Syndrome (HPS) Chediak-Higashi Syndrome (CHS)
OA1 X-Linked Ocular Albinism Autosomal Recessive Ocular Albinism (AROA)
Common Questions About Albinism
Can people with albinism have children? Do people with albinism have a normal life span? Do people with albinism have normal intelligence? Where can I get more information about albinism? What Causes Albinism? Why are children born with it?
Understanding Genetics
Understanding Genetics Autosomal Recessive Inheritance X-Linked Inheritance
Miscellaneous
Other Reading: Definitions of Words About the Authors
 
Questions & Answers:
What is Albinism?
The word “albinism” refers to a group of inherited conditions. People with albinism have little or no pigment in the eyes, skin, and hair (or in some cases in the eyes alone). They have inherited from their parents an altered copy of a genes that does not work correctly. The altered gene does not allow the body to make the usual amounts of a pigment called melanin.
Approximately one in 17,000 people have one of the types of albinism. About 18,000 people in the United States are affected. Albinism affects people from all races. 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.
What is melanin pigment?
Melanin is a dark compound that is called a photoprotective pigment. The major role of melanin pigment in the skin is to absorb the ultraviolet (UV) light that comes 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 and do not tan with exposure to the sun. As a result, their skin is sensitive to the sun light and they develop a sun burn. In people with albinism, all other parts of the skin are normal even if there is no melanin in the skin.
Melanin pigment is important in other areas of the body, such as the eye and the brain, but it is not known what the melanin pigment does in these areas. Melanin pigment is present in the retina (RET-n-ah), and the area of the retina called the fovea (FOE-vee-ah) does not develop correctly if melanin pigment in not present in the retina during development (see below). The other areas of the retina develop normally whether or not melanin pigment is present. The nerve connections between the retina and the brain are also altered if melanin pigment is not present in the retina during development. The iris has melanin pigment and this makes the iris opaque to light (no light goes through an opaque iris). Iris pigment in albinism is reduced, and the iris is translucent to light, but the iris develops and functions normally in albinism.
How does melanin form? (see Melanin Pathway Figure)
Melanin forms in a special cell called the melanocyte. This cell is found in the skin, in the hair follicle, and in the iris and retina of the eye. There are many steps in the process of converting the amino acid tyrosine to melanin pigment. As can be seen in the figure of the melanin pathway, two types of melanin form: black-brown eumelanin (YOU-melanin) and red-blond pheomelanin (FEE-O-melanin).
As with most metabolic pathways in our body, the first compound in a pathway is converted to the next compound by the action of an enzyme. For example, in the simple pathway A–>B–>C, the conversion of compound A to B occurs because of the action of Enzyme 1, and the conversion of B to C occurs because of the action of Enzyme 2. The formation of melanin pigment follows a pathway like this, but the pathway is more complex and not all of the steps are known.

Tyrosinase (tie-ROW-sin-ace) is the major enzyme involved in the formation of melanin pigment. Tyrosinase is responsible for converting tyrosine to DOPA and on to dopaquinone (dopa-QUIN-own). The dopaquinone then forms black-brown eumelanin or red-yellow pheomelanin. The tyrosinase enzyme is made by the tyrosinase gene on chromosome 11, and alterations (also called mutations) of this gene can produce one type of albinism because the tyrosinase enzyme made by the altered gene does not work correctly.
Two additional enzymes called tyrosinase-related protein 1 or DHICA oxidase (DEE-ca OX-eye-dase) and tyrosinase-related protein 2 or dopachrome tautomerase (dopa-chrome tow-TOM-er-ace) are important in the formation of eumelanin pigment. The gene for DHICA oxidase in on chromosome 9 and the gene for dopachrome tautomerase in on chromosome 9. Alterations of the DHICA oxidase gene are associated with a loss of function of this enzyme and this produces on type of albinism. Alterations of the gene for dopachrome tautomerase do not produce albinism.
Three other genes make proteins that are also involved in melanin pigment formation and albinism, but the exact role of these proteins remains unknown. These genes are the P gene on chromosome 15, the Hermansky-Pudlak syndrome gene on chromosome 10, and the ocular albinism gene on the X chromosome.

What Are the Problems with Albinism?
The eye needs melanin pigment to develop normal vision. People with albinism have impairment of vision because the eye does not have a normal amount of melanin pigment during development. The skin needs pigment for protection from sun damage, and people with albinism often sunburn easily. In tropical areas, many people with albinism who do not protect their skin get skin cancers.
There are several less common types of albinism which involve other problems also, such as mild problems with blood clotting, or problems with hearing. (See discussion of types of albinism below.)
Albinism may cause social problems, because people with albinism look different from their families, peers, and other members of their ethnic group.
Growth and development of a child with albinism should be normal and intellectual development is normal. Developmental milestones should be achieved at the expected age. General health of a child and an adult with albinism is normal, and the reduction in melanin pigment in the skin, hair and the eyes should have no effect on the brain, the cardiovascular system, the lungs, the gastrointestinal tract, the genitourinary system, the musculoskeletal system, or the immune system. Life span is normal.
What Eye Problems Result from Albinism
People with albinism, whether it involves the eyes alone or involves the skin and the hair, often have several problems:

  • People with albinism are not “blind,” but their vision (also called visual acuity) is not normal, and cannot be corrected completely with glasses. Extreme far-sightedness or near-sightedness, and astigmatism are common (see definitions below) and correction with glasses can improve acuity in many people with albinism. Corrected visual acuity ranges from 20/20 (can see at 20 feet what should be seen at 20 feet; normal) to 20/400 (see at 20 feet what should be seen at 400 feet; legally blind). Normal or near-normal vision is unusual, however, even when glasses are worn.
  • Nystagmus (nye-STAG-muss), which is an involuntary movement of the eyes back and forth. Many people with albinism learn to use a head tilt or turn that decreases the movement and may improve vision.
  • Strabismus (strah-BIZZ-muss), which means that the eyes do not fixate and track together. Despite this condition, people with albinism do have some depth perception, although it is not as sharp as when both eyes can work together.
  • Sensitivity to light, which is called photophobia (FOE-tow-FOE-bee-ah). The iris allows “stray” light to enter the eye and cause sensitivity. Contrary to a common idea, this sensitivity does not limit people with albinism from going out into the sunlight.

  • Iris color is usually blue/gray or light brown (Diagram 1). It is a common notion that people with albinism must have red eyes, but in fact the color of the iris varies from a dull gray to blue to brown. (A brown iris is common in ethnic groups with darker pigmentation.) Under certain lighting conditions, there is a reddish or violet hue reflected through the iris, which has very little pigment. This reddish reflection comes from the retina, which is the surface lining the inside of the eye. This reddish reflection is similar to that which occurs when a flash photograph is taken of a person looking directly at the camera, and the eyes appear red. With some types of albinism the red color can reflect back through the iris as well as through the pupil.
  • One major abnormality of the eye in albinism involves lack of development of the fovea (also known as foveal hypoplasia) (Diagram 2). The fovea is a small but most important area of the retina in the inside of the eye. The retina contains the nerve cells that detect the light entering the eye and transmit the signal for the light to the brain. The fovea is the area of the retina which allows sharp vision, such as reading, and this area of the retina does not develop in albinism. It is not known why the fovea does not develop normally with albinism, but it is related to the lack of melanin pigment in the retina during development of the eye. The developing eye seems to need melanin for organizing the fovea.

  • The major abnormality of the eye in albinism involves the development of the nerves that connect the retina to the brain. People with albinism have an unusual pattern for sending nerve signals from the eye to the brain (Diagram 3). The nerve connections from the eye to the vision areas of the brain are organized differently from normal (see Diagram 3). This unusual pattern for nerve signals probably prevents the eyes from working well together, and causes reduced depth perception.
  • Strabismus (straw-BIS-mus) is also common in albinism and is related to the altered development of the optic nerves. The strabismus in albinism is usually not severe and the tends to alternate between involving the right and the left eye.


What Can be Done for the Eye Problems?
Ophthalmologists and optometrists can help people with albinism compensate for their eye problems, but they cannot cure them.
For help with visual acuity, eye doctors experienced in low vision can prescribe a variety of devices. No one device can serve the needs of all persons in all situations, since different occupations and hobbies require the use of vision in different ways. Young children may simply need glasses, and older children can sometimes benefit from bifocal glasses. Low vision clinics may prescribe telescopic lenses mounted on glasses, sometimes called bioptics, for close-up work as well as for distant vision. Recently smaller and lighter telescopes have been developed; however, ordinary glasses or bifocals with a strong reading correction may serve well for many people with albinism.
For nystagmus, research has searched for an effective treatment which helps in all cases. Attempted treatments to control nystagmus have included biofeedback, contact lenses, and surgery. The most promising may be eye muscle surgery that reduced the movement of the eyes; however, vision may not improve in all cases due to other associated eye abnormalities. People with albinism may find ways of reducing nystagmus while reading, such as placing a finger by the eye, or tilting the head at an angle where nystagmus is dampened.
For strabismus, ophthalmologists prefer to treat infants starting at about six months age, before the function of their eyes has developed fully. They may recommend that parents patch one eye to promote the use of the non-preferred eye. In other cases, the alignment of the eyes improves with the wearing of glasses. Correction of strabismus by surgery or by injection of medicine into the muscles around the eyes does not completely correct the problem with both eyes fixing on one point. Although these treatments may improve the alignment of the eyes and enhance psycho-social development and interpersonal interactions, they cannot correct the improper routing of the nerves to the brain. Depth perception is not improved with eye muscle surgery.
For photophobia, eye doctors can prescribe dark glasses that shield the eyes from bright light, or photochromic lenses that darken on exposure to brighter light. There is no proof that dark glasses will improve vision, even when used at a very early age, but they may improve comfort. Many children and adults with albinism do not like tinted lenses, and benefit more from wearing a cap or a visor when outdoors in the sun.
What Can be Done to Help Children with Albinism in School?
Most children with albinism should function in a mainstream classroom environment, provided the school gives specific attention to their special needs for vision. Contact with the school system should begin well before kindergarten, since school systems provide preschool services to children with disabilities. Preschool evaluations allow parents and teachers to form an Individual Education Plan for the child. The use of Braille is not necessary, and, if a trial of Braille is given, children with albinism will read the dots visually.
Children with albinism often prefer to read with a head tilt and usually hold the page close to the eyes. Occasionally it can be difficult to get them to use their glasses, as they do not notice significant improvement in their vision when glasses are used. Furthermore, use of glasses or books with large print can be difficult because of peer pressure.
Various classroom aids help children with albinism:

  • High contrast written material: Children with albinism have a hard time reading worksheets and papers that are light or low contrast. Black on white high contrast material is better.
  • Large-type textbooks: The school can usually obtain large type editions from the publishers of their regular textbooks. Because children. with albinism often have difficulty keeping track of their place on the page while shifting back and forth between a textbook and a worksheet, it may help to allow them to write in the textbook. Worksheets may need to be copied on a machine that enlarges print size. Children with albinism do not always need large-type materials, however, and large type should not substitute for poor optical visual aids. Use of audio tapes may be preferable to voluminous reading.
  • Copies of the teacher’s board notes: The child with low vision can read the notes close-up while classmates read the board.
  • Various optic devices: Hand-held monoculars, telescopic lenses mounted over eye glasses, video enlargement machines (closed circuit TV), and other types of magnifiers may help some people with albinism.
  • Computers: Children with albinism should begin key-boarding skills early, since computers with software for large character screen display can help greatly with writing projects.

Prescription of appropriate classroom visual aids requires teamwork of the student, parent, classroom teacher, vision resources teacher, and an optometrist or ophthalmologist experienced in working with persons with low vision. The American Foundation for the Blind (15 West 16th Street, New York, NY 10011) maintains a directory of low vision clinics in the United States.
How Much Time Can a Person with Albinism Stay in the Sun?
Most people with albinism do not tan, and they burn easily on exposure to the sun. People with albinism who develop increasing amounts of hair and skin pigment as they get older may not be bothered by the sun, and may tan with sun exposure. If sun exposure produces a sunburn, then the skin must be protected to prevent burning and damage.
Sunburn is skin damage from exposure to ultraviolet light, which is a part of sunlight that is not visible to the human eye. Redness develops 2 to 6 hours after exposure to ultraviolet light, and sunburn may not turn completely red until as long as 24 hours after the exposure. As a result a sunburn can worsen after a person leaves the sun. Prolonged sun exposure in a person who does not tan well is associated with the development of skin cancer. This can be prevented with correct protection of the skin from the ultraviolet radiation of the sun.
It is difficult to state a general rule for the number of hours in the sun that people with albinism can tolerate, since the intensity of the ultraviolet light varies a great deal, depending upon the time of day and year, and the environmental conditions:

  • Latitude: A person who can tolerate one hour of sun in Florida without burning can tolerate two hours of sun in New Jersey under the same conditions.
  • Altitude: Each 1000-foot increase in altitude adds 4% to the intensity of the sunburning rays. The intensity of sunlight at 5000 feet is about 20% greater than at sea level.
  • Surroundings: Sand reflects 25% or more of ultraviolet rays, so that it is possible to get sunburned while sitting in the shade on a beach. Fresh snow reflects 70 to 90% of ultraviolet rays. Reflected light may burn areas which are usually shaded, such as those under the nose or chin.
  • Weather: A bright day with a thin cloud cover has 60 to 80% of the ultraviolet rays present on a clear day. Clouds can cool and give a false impression that there is little risk of sunburn.
  • Water: As much as 96% of ultraviolet rays can penetrate clear water.
  • Season: The greatest intensity of ultraviolet light occurs at the summer solstice, about June 22. May 1 has as much intensity as August 15.
  • Time of day: Most ultraviolet rays come between 10 a.m. and 2 p.m. Standard Time, or 11 a.m. and 3 p.m. Daylight Savings Time.
  • Clothing: Up to 50% of the ultraviolet rays can go through wet clothing, such as tee shirts worn for swimming. Colored clothing and denser-woven clothing allow less light penetration. Some tee shirts, such as Frogskin¨ tee shirts, are designed to protect against sun even when wet.

How Well Do Sunscreens Work for People with Albinism?
We are currently up-dating this section on sunscreens. For more information, go to this report on sunscreens provided by the NOAH Website.
How do we classify albinism?
Two main categories of albinism are: “oculocutaneous albinism” (AHK-you-low-CU-tain-ee-us) or “OCA” which means that melanin pigment is missing in the skin, the hair, and the eyes; and “ocular albinism” (AHK-you-lahr) or “OA” which means that the melanin pigment is missing mainly in the eyes, and the skin and hair appear normal. OCA is more common than OA.
How do we classify Oculocutaneous Albinism?
The classification of OCA has changed a great deal over the years, with much of the work coming from the International Albinism Center and the help of all of the wonderful individuals and families who have helped with these studies. For many years, the term “albinism” referred only to people who had white hair, white skin, and blue eyes. Individuals who had OCA and pigmented hair and eyes were identified, particularly in the African and African-American population, and terms such as ‘incomplete albinism’, ‘partial albinism’ or ‘imperfect albinism’ were used for this, but these terms are inappropriate and are no longer used. In the 1960’s, Dr. Carl Witkop developed the hairbulb incubation test to separate pigmenting and non-pigmenting types of OCA and started to use the terms “ty-neg” or “tyrosinase-negative” and “ty-pos” or “tyrosinase-positive” OCA. Freshly plucked hairbulbs from a person with OCA were placed in a solution of tyrosine or dopa (see Pathway above) in a test tube and watched to see if pigment formed in the pigment cells in the hairbulb. If no pigment formed, the test was negative and the diagnosis was ty-neg OCA. If pigment formed in the hairbulb, the test was positive and the diagnosis was ty-pos OCA. Although this simple test showed that there were different types of OCA, subsequent studies have shown that the hairbulb incubation test is not very sensitive and has many false negative and false positive responses. As a result, the hairbulb incubation test is no longer used in the evaluation of an individual with OCA.
A sensitive hairbulb tyrosinase enzyme activity assay was developed in an attempt to improve the specificity of the hairbulb test. Unfortunately, biochemical studies of hairbulb tyrosinase activity also proved to be unreliable and did not have the specificity necessary for accurate diagnosis. The hairbulb tyrosinase assay test is no longer used in the evaluation of an individual with OCA.
In the 1980’s the classification of OCA was expanded using very careful skin, hair, and eye examinations. The reason for this was the knowledge that there were more than 50 gene loci that controlled pigmentation in the mouse, and it was suggested that careful analysis of skin, hair, and eye pigmentation of individuals with OCA could help identify the human equivalent of each of these genes. A number of types of OCA were identified, including platinum OCA, minimal pigment OCA, yellow OCA, temperature-sensitive OCA, autosomal recessive ocular albinism and brown OCA, and it was hoped that each would be caused by a different gene. In the 1990’s, we have been able to identify the genes involved in most types of OCA, and have found that the classifications based on hair, skin and eye color is not accurate and that it was better to classify OCA types based on the specific gene involved.
We have now identified five genes that are associated with the development of OCA and one gene that is involved in OA.

The pigmentation (phenotype) range for OCA at each gene locus is broad. Most of the various types or subtypes of OCA that were defined over the past 20 years can now be associated with a specific genetic locus.
OCA1. Tyrosinase Related Oculocutaneous Albinism.
One of the two most common types of albinism is tyrosinase related OCA, produced by loss of function of the tyrosinase enzyme in the melanocyte. This results from inherited mutations of the tyrosinase gene. Classical OCA, with a total absence of melanin in the skin, hair and eyes over the lifetime of the affected individual is the most obvious type of OCA1, but there is a wide range of pigmentation associated with tyrosinase gene mutations. The range in phenotypes extends from total absence to near normal cutaneous pigmentation, but the ocular features are always present and help identify an individual as having albinism.
Many different mutations of the tyrosinase gene have been identified in individuals and families with OCA1. Most mutations lead to the production of tyrosinase enzyme that does not work. As a result, the first two critical conversions in the melanin pathway (tyrosine–>dopa–>dopaquinone) are not made and no melanin pigment forms; the pathway is “blocked” at the start. Mutations that produce an inactive enzyme or no enzyme at all are called “null” mutations.
Some tyrosinase gene mutations are not null mutations but are called “leaky” mutations. These mutations lead to the production of a tyrosinase enzyme that has a little activity but nowhere near the normal amount of activity (often in the range of 1-10% of normal activity). Leaky mutations and the resultant tyrosinase enzyme allow some melanin to form. The formation of melanin can be very small (the minimal pigment type of OCA) or can range to nearly normal (the type of OCA that was mistakenly called autosomal recessive ocular albinism).
An important distinguishing characteristic of OCA1 is the presence of marked hypopigmentation at birth. Most individuals affected with a type of OCA1 have white hair, milky white skin, and blue eyes at birth. The irides can be very light blue and translucent such that the whole iris appears pink or red in ambient or bright light. During the first and second decade of life, the irides usually become a darker blue and may remain translucent or become lightly pigmented with reduced translucency. The skin remains white or appears to have more color with time. Sun exposure produces erythema and a burn if the skin is has little pigment and is unprotected, but may tan well if cutaneous pigment has developed. Pigmented lesions (nevi, freckles, lentigines) develop in the skin of individuals who have developed pigmented hair and skin.
OCA1A.
Individuals with OCA1A or the classic tyrosinase-negative OCA are unable to make melanin in their skin, hair or eyes, because they have no active tyrosinase enzyme. They are born with white hair and skin and blue eyes, and there is no change as they mature into teenagers and adults. They never develop melanin in these tissues. The phenotype is the same in all ethnic groups around the world and at all ages. With time, the hair may develop a dense rather than a translucent white or a slight yellow tint but this usually from the denaturing of the hair protein with the use of different shampoos. The irides are translucent and appear pink early in life and often turn a gray-blue color with time. No pigmented lesions develop in the skin, although amelanotic nevi can be present.
Visual acuity for OCA1A is usually in the legally-blind range, 20/200 to 20/400, although near vision may be better if the print is held close to the eyes. Vision usually does not improve with age. Photophobia and nystagmus cause more problems with OCA1A than with other types. Vision often does not correct well with glasses, but low vision aids help.
OCA1B.
OCA1B is produced by mutations of the tyrosinase gene that result in enzyme with some residual or “leaky” activity. The variation in the pigmentation in individuals with OCA1B is wide from very little cutaneous pigment to nearly normal skin and hair pigment. Mutations coding for enzyme with differing amounts of residual activity are the primary cause of this variation, and a moderate amount of residual activity can lead to near normal cutaneous pigmentation and the mistaken diagnosis of ocular albinism. Ethnic and family pigment patterns influence the pigmentation of an individual with OCA1B, and hair color can be light red or brown in some families where this is the predominant pigment pattern.
The original OCA1B phenotype was called yellow albinism because of the yellow blond or golden color of the melanin that develops in the hair of affected individuals. It is now known that the hair color is the result of pheomelanin synthesis (see pathway above), and the formation of this type of melanin is related to the reduced tyrosinase function. Only small amounts of dopaquinone form and these combine quickly with sulfur-containing compounds present in the cell and produce the pheomelanins. Other types of OCA1B have been described as minimal pigment OCA, platinum OCA, temperature-sensitive OCA, and autosomal recessive ocular albinism.
All variations of OCA1B are characterized by having very little or no pigment present at birth followed by the development of varying amounts of melanin in the hair and the skin in the first or second decade. In some cases, the melanin develops within the first year. The hair color changes to light yellow, light blond or golden blond first, and may eventually turn dark blond or brown in the adolescent and the adult. One interesting feature of OCA1B is the development of dark eyelashes. Eyelash hair pigment is often darker than that of the scalp hair. The irides can develop hazel, light tan or brown pigment, sometimes limited to the inner third of the iris, and iris pigment can be present on globe transillumination. Some degree of iris translucency, as demonstrated by slit-lamp examination, is usually present. Visual acuity is in the range of 20/90 to 20/400, and may improve with age.
Many individuals with OCA1B will tan with sun exposure while it is more common to burn without tanning after sun exposure. Pigmented nevi can develop with time, although most developing nevi are amelanotic. Very few freckles develop.
Another type of OCA1B is temperature-sensitive OCA. Affected individuals are thought to have OCA1A during the first years of life, with white hair and skin, and blue eyes. With further development, some of the body hair develops pigment. The hair under the arms remains white and the scalp hair remains white but may develop a slight yellow tint. In contrast to this is the arm and leg hair that develop light to dark pigment. The eyes stay blue and the skin remains white and does not tan. This type of OCA1B is caused by a mutation of the tyrosinase gene that produces an enzyme that does not work at regular body temperature (scalp and under the arms) but does work in cooler parts of the body (arms and legs). As a result, melanin synthesis occurs in the cooler but not the warmer areas of the body such as the arms and legs.
Autosomal recessive ocular albinism.
Some years ago a series of families were described in which children of normally pigmented parents had the ocular features of albinism but did not appear to have significant cutaneous hypopigmentation. This was called autosomal recessive ocular albinism (AROA) because males and females were affected in these families. Studies now show that calling this AROA is not correct and most of the individuals and families like this have OCA1B or OCA2 with nearly normal or normal cutaneous pigmentation. One family has been described in which the individual with OCA1B was not diagnosed with albinism until mid-life, although she had always been aware of her reduced visual acuity.
OCA2 P-Gene Related Oculocutaneous Albinism
The common features of OCA2 include the presence of hair pigment at birth and iris pigment at birth or early in life. Localized (nevi, freckles, and lentigines) skin pigment can develop, often in sun exposed regions of the skin, but tanning is usually absent. It was once thought that the ethnic and constitutional pigment background of an affected individual had a more profound effect on the OCA2 phenotype than on the OCA1 phenotype, but this no longer appears to be the case. Both OCA1B and OCA2 have a broad range of pigmentation that, in part, reflects the genetic background of the affected individual. There may be some accumulation of pigment in the hair with age but this is much less pronounced as that found in OCA1B, and many individuals with OCA2 have the same hair color throughout life. OCA2 is the most common type of OCA in the world, primarily because of the high frequency in equatorial Africa .
In Caucasian individuals with OCA2, the amount of pigment present at birth varies from minimal to moderate. The hair can be very lightly pigmented at birth, having a light yellow or blond color, or more pigmented with a definite blond, golden blond or even red color. The normal delayed maturation of the pigment system in northern European individuals (i.e., very blond or towheaded as a child with later development of dark blond or brown hair) and lack of long hair can make the it difficult to distinguish OCA1 from OCA2 in the first few months of life. The skin is white and does not tan on sun exposure. Iris color is blue-gray or lighted pigmented, and the degree of iris translucency correlates with the amount of pigment present. With time, pigmented nevi and lentigines may develop and pigmented freckles are seen in exposed areas with repeated sun exposure. The hair in Caucasian individuals may slowly turn darker through the first two or more decades of life.
There is a distinctive OCA2 phenotype in African-American and in African individuals. The hair is yellow at birth and remains yellow through life, although the color may turn darker. Interestingly, the hair can turn lighter in older individuals, and this probably represents the normal graying with age. The skin is white at birth with little change over time, and no tan develops. Localized pigmented lesions such as pigmented nevi, lentigines and freckles can develop in some individuals. The irides are blue/gray or lightly pigmented.
There appears to be a wide OCA2 pigment phenotypic range in African-Americans, in that some individuals with OCA2 (defined as having pigmented hair at birth and the ocular features of albinism) have brown, ginger, auburn or red hair. Some of this variation may reflect genetic admixture in this population, and some may result from different mutations of the P gene and their different effect on the function of the P protein. Some individuals who were previously thought to have autosomal recessive ocular albinism have now been shown to have OCA2.
Brown OCA
Brown OCA is a type of albinism that is recognized in the African and the African-American populations, but not in other populations to date. In African and African-American individuals with Brown OCA, the hair and skin color are light brown, and the irides are gray to tan at birth. With time there is little change in skin color, but the hair may turn darker and the irides may accumulate more tan pigment. Affected individuals are recognized as having albinism because they have all of the ocular features of albinism. The iris has punctate and radial translucency, and moderate retinal pigment is present. The skin may darken with sun exposure. Visual acuity ranges from 20/60 to 20/150. The phenotype in Caucasian individuals is unknown at present.
Brown OCA is part of the spectrum of OCA2, resulting from alterations of the P gene. These gene alterations are associated with the development of yellow or red pheomelanin and a lack of development of brown or black eumelanin. As with OCA1B, Brown OCA may arise from a mutation that reduces (“leaky” mutation)the function of the P gene product while the more common OCA2 results from completely knocking out (“null” mutation) the function of the P protein.
Prader-Willi and Angelman Syndrome.
There is an association with OCA2 and the hypopigmentation found with Prader-Willi syndrome and Angelman Syndrome. Prader-Willi syndrome is a developmental syndrome with neonatal hypotonia, hyperphagia and obesity, hypogonadism, small hands and feet, and mental retardation associated with characteristic behavior. Many individuals with Prader-Willi syndrome are hypopigmented but most do not have the typical ocular features of albinism, but a number of individuals with Prader-Willi syndrome and OCA have been identified. For those without obvious OCA, hair and skin are lighter than unaffected family members, and childhood nystagmus and strabismus are common and often transient. The irides are pigmented with some translucency on globe transillumination, and retinal pigment is reduced in amount. The fovea may not appear entirely normal but is usually present. Some individuals with Prader-Willi syndrome have OCA2 with cutaneous hypopigmentation associated with all of the typical ocular features of albinism.
Angelman syndrome is a complex developmental disorder that includes developmental delay and severe mental retardation, microcephaly, neonatal hypotonia, ataxic movements, and inappropriate laughter. In Angelman syndrome, the hypopigmentation is characterized by light skin and hair. There may be a history of nystagmus or strabismus, and iris translucency and reduced retinal pigment may be present. No analysis of the optic tract organization is available. It is expected that individuals with Angelman syndrome having OCA2 will be described, because of the location of the P gene in the Prader-Willi/Angelman syndrome region of chromosome 15.
OCA3 TRP1-Related OCA
The first evidence that variations in human pigmentation could be related to mutations of the TRP1 gene came from the description of an African-American newborn twin boy who had light brown skin, light brown hair, and blue/gray irides while his fraternal twin brother had normal pigmentation. Subsequent studies have shown that a type of OCA known as ‘Rufous’ or ‘Red OCA’ in the South African population results from mutations of the gene for TRP1.
Rufous or red OCA has only been partially documented. Individuals with OCA who have red hair and reddish-brown pigmented skin have been reported in Africa and in New Guinea, but clinical descriptions are incomplete, and similar individuals in the U.S. population have not been identified and reported. The cases are described in the literature as ‘red’, ‘rufous’, or ‘xanthous’ albinism. Individuals with red hair who have either OCA1 or OCA2 are also recognized, but the reddish-brown skin pigment is usually not present, and they should not be confused with Rufous OCA.
The pigment phenotype in South African individuals includes red or reddish brown skin, ginger or reddish hair, and hazel or brown irides. The ocular features are not fully consistent with the diagnosis of OCA, however, as many do not have iris translucency, nystagmus, strabismus, or foveal hypoplasia. Furthermore, no misrouting of the optic nerves has been demonstrated by a visual evoked potential, suggesting either that this is not a true type of albinism, or that the hypopigmentation is not sufficient to consistently alter optic nerve development. At this time, the phenotype for TRP1-related OCA in the Caucasian and the Asian populations is unknown.
Hermansky Pudlak Syndrome (HPS)
The Hermansky-Pudlak Syndrome includes OCA, an abnormality of platelets that usually leads to mild bleeding, and the accumulation of a material called ceroid in tissues throughout the body. Hermansky and Pudlak first described this condition in two Czechoslovakian individuals in 1959 and it has subsequently been recognized throughout the world, with the majority of affected individuals in the Puerto Rican population. HPS is not common, except in the latter population, and does not constitute a major type of OCA; however, the frequency in Puerto Rico is approximately 1:1,800. HPS is not found on other Caribbean islands.
HPS is a pigmenting type of OCA and skin and eye pigment develop in many affected individuals, but the amount of pigment that forms is quite variable. Some affected individuals have marked hypopigmentation of their skin and hair similar to that of OCA1A, others have white skin and yellow or blond hair similar to OCA1B or OCA2, and others have only moderate hypopigmentation suggesting that they may have OA rather than OCA. The variation can be seen within families as well as within families.
Individuals with HPS in the Puerto Rican population have hair color that varies from white to yellow to brown. Skin color is creamy white and definitely lighter than individuals without HPS in this population. Freckles are often present in the sun exposed regions (face, neck, arms and hands), often enlarging and overlapping into large areas that look like normal dark skin pigment, but tanning does not occur. Pigmented nevi are common. Iris color varies from blue to brown, and all of the ocular features of albinism are present. Visual acuity ranges from 20/60 to 20/400.
Affected individuals have been identified in other populations infrequently, and the phenotype shows the same degree of variation in pigmentation as is found in Puerto Rico. Hair color varies from white to brown, and this correlates with the ethnic group. The skin is white and does not tan. Eye color varies from blue to pigmented.
The most important medical problems in HPS are usually related to the lung and the gastrointestinal tract changes. Interstitial lung fibrosis (or scarring of the lungs) develops in many individuals with HPS, although the actual prevalence is unknown. The fibrosis results in an inability of the lungs to expand and contract, reducing their ability to take in oxygen and exhale carbon dioxide. This is called restrictive lung disease. Fewer individuals with HPS develop colitis of inflammation of the intestinal tract. This is called granulomatous colitis, and the medical problems include abdominal pain and bloody diarrhea in a child or an adult. The presence of ceroid material in the lungs and the intestines suggest that this material may be involved in the development of these complications, but this has not been proven.
The bleeding problem in HPS is related to a deficiency of granules in the platelets (i.e. storage pool-deficient platelets) that store material needed for normal platelet function. Platelets are cells in the blood that are responsible for forming the initial clot after a blood vessel is cut or opened. Platelets work by first attaching to exposed material in the blood vessel wall, and then sticking together and contracting into a small plug to close the hole. Platelets stick together because they secrete chemicals from storage compartments that are inside each platelet. In HPS, these storage compartments do not form (storage granules do not form) and the platelets are unable to secrete this necessary chemicals. The platelets first stick to the cut blood vessel wall but do not aggregate and contract and do not form a firm plug at the hole. This produces mild bleeding episodes in many affected individuals, including easy brusibility, epistaxis (bloody nose), hemoptysis (bloody sputum), bleeding of the gums with brushing or dental extraction, and postpartum bleeding. Occasional severe bleeding is observed which in part may be related to normal variation in von Willibrand factor.
Chediak-Higashi Syndrome (CHS)
The Chediak-Higashi Syndrome is a rare syndrome that includes an increased susceptibility to bacterial infections, hypopigmentation, and the presence of giant granules in white blood cells. The skin, hair, and eye pigment is reduced or diluted in CHS but the affected individuals often do not have obvious albinism and the hypopigmentation may only be noted when compared to other family members. Hair color is light brown to blond, and the hair has a metallic silver-gray sheen. The skin is creamy white to slate gray. Iris pigment is present and nystagmus and photophobia may be present or absent
OA1 X-Linked Ocular Albinism
Ocular albinism involves the eyes only. X-linked ocular albinism occurs primarily in males. Skin color is usually normal or slightly lighter than the skin of other family members. Eye color may be in the normal range, but examination of the back of the eye (retina) through the pupil shows that there is no pigment in the retina. Females who carry the gene for X-Linked ocular albinism may show a mixture of pigmented and non-pigmented areas in their retinas.
Visual acuity in X-Linked albinism is in the range of 20/50 to 20/400.
It is often possible to identify females who carry the gene by examining their eyes. “X-Linked” means that the gene for ocular albinism is passed from mothers who carry the gene to sons who have ocular albinism. See appendix, “Understanding Genetics“, for an explanation of the way X-Linked inheritance works.
Autosomal Recessive Ocular Albinism (AROA)
In the 1970’s, a type of albinism associated with relatively normal skin and hair pigment was described in families that contained affected females and males. This appeared to be a type of ocular albinism that was caused by a gene on an autosome chromosome (non-sex chromosome) rather than on the X chromosome; hence, the name of autosomal recessive ocular albinism. We now know that this was incorrect and these families are actually part of the spectrum found in OCA1 and OCA2. At this time, there is no evidence for a true AROA type of albinism, and this term should not be used.
How can you determine the type of albinism present?
It is usually possible to determine the type of albinism present with a careful history of pigment development and an examination of the skin, hair and eyes. The only type of albinism that has white hair at birth is OCA1. Individuals with other types of OCA will have some hair pigment at birth, although it may be very slight in amount. It can be difficult to tell if the hair is completely white or very lightly pigmented in a very young child, and changes in pigment over time will usually help clarify the OCA type present.
The most accurate test for determining the specific type of albinism is a gene test. A small sample of blood is obtained from the affected individual and the parents as a source of DNA, the chemical that carries the ‘genetic code’ of each gene. By a complex process, a genetic laboratory can “sequence” the code of the DNA, to identify the changes (mutations) in the gene that cause albinism in the family. The test is useful only for families that contain individuals with albinism, and cannot be performed practically as a screening test for the general population. None of the tests available are capable of detecting all of the mutations of the genes that cause albinism, and responsible mutations cannot be detected in a small number of individuals and families with albinism.
The test can be used to determine if a fetus has albinism. For this purpose a sample would be obtained by amniocentesis, a procedure which involves using a needle to draw fluid from the uterus, at 16 to 18 weeks gestation. Those considering such testing should be aware that given proper support children with albinism can function well and have normal life spans.
For information about these tests, contact:
The International Albinism Center
612-625-4400.
Common Questions About Albinism
Can people with albinism have Children
Albinism does not limit the ability of an individual with albinism to have children. The children may or may not have albinism, depending on the genes in partner of the affected individual (see “Understanding Genetics” below).
Do people with albinism live a normal lifespan?
In general, people with albinism have a normal lifespan. Any medical problems are similar to those in the rest of the population. Skin cancer may occur, but is usually curable.
Do people with albinism have normal intelligence?
Albinism does not cause mental impairment or developmental delay. Individuals with albinism pursue a wide range of career; their options are limited only by their visual impairment. A child or an adult with albinism who has developmental problems must be evaluated for another cause of these problems, because developmental delays of problems are not expected with albinism.
Where Can I Get More Information about Albinism?
The International Albinism Center University of Minnesota P.O. Box 485 Mayo, 420 Delaware Street S.E. Minneapolis, Minnesota 55455
This is a center for research about albinism and health care for albinism.
NOAH, the National Organization for Albinism and Hypopigmentation 1530 Locust Street, #29 Philadelphia, PA 19102-4415 Phone: 800-473-2310. This organization provides information and support for persons with albinism, their families, and health professionals. NOAH publishes a newsletter and information bulletins about albinism, answers individual questions, and conducts conferences.
What Causes Albinism? Why are children born with it?
Albinism is genetic. It is inherited. It is passed on from one generation to the next in the genes. Genes are contained in the egg and the sperm that combine at conception to start the process of forming a baby. Genes act as blueprints that tell the system how to do its work. In the case of albinism, the genes involved are those that tell the eyes or skin how to make melanin pigment.
Each cell in the body has two copies of each gene- one version from the mother and one version from the father. For OCA, the individual with albinism has received an albinism gene from both parents, and both versions of his blueprint for making pigment are incorrect.
If a person carries one normal copy of a gene and one altered or albinism copy of a gene, he or she still has one blueprint that will provide enough information to make pigment. That means that he or she will have normal eye and skin color. For OCA, parents carry an albinism gene with an incorrect version of the blueprint, but they have normal pigmentation, because they still have one normal gene with a normal version of the blueprint.
About 1 in 70 people carries a gene for OCA. Suppose a man and a woman each carry an altered copy of the same gene and have normal coloration. They each have a normal copy and an albinism copy of the gene, and will pass one of these two copies when they conceive a baby. They each have a 1 in 2 chance of passing on the albinism copy of the gene to their baby. As a result, for each pregnancy there is a 1 in 4 chance (1/2 x 1/2) that their baby will get two copies of the gene for albinism, in which case the baby will have no normal blueprint for making pigment, and will have albinism. This description of the inheritance of albinism applies to the different types of OCA. See the section “Understanding Genetics”, for a more detailed discussion. There are five genes known that can cause OCA, and there many be several additional OCA genes that have not been identified to date. If you wish specific information about your chances for having a child with albinism, seek advice from a qualified genetics counselor.
Understanding Genetics
Understanding Genetics:
An individual’s development is directed by the genetic information that he or she has received from both parents. This genetic information is carried in every cell of the human body on structures called chromosomes Human cells contain 46 chromosomes which are present in 23 separate pairs. The only exception to this rule involves the reproductive cells. Sperm cells and egg cells contain only 23 chromosomes, one from each of the 23 pairs. We receive one of each of our chromosome pairs from our mother through her egg cell, and one of each of our chromosome pairs from our father through his sperm cell.

Figure 4 and Figure 5 are pictures of human chromosomes. The first 22 pairs of chromosomes are called autosomes. They are numbered according to size, with chromosome #1 being the largest chromosome and chromosome 22 the smallest chromosome. These are the non-sex chromosomes. The 23rd pair is the sex chromosome pair. Females have two X chromosomes, and males have one X and one Y chromosome.
Each chromosomes is composed of many hundreds or thousands of genes. Genes are biochemical blueprints which code for products needed to produce and maintain human life. Genes account for physical traits as well as cellular chemical reactions, which direct the production and maintenance of our body systems. As we have two of each of the autosomes, one from each parent, we have two of each of the genes located on the autosomes, one from each parent. Females have two copies of every gene located on the X chromosome, while males have one copy of the genes on the X chromosome and one copy of the genes on the Y chromosome.

Autosomal Recessive Inheritance:
The term autosomal means the gene responsible for the condition or trait is located on one of the non-sex chromosomes or autosomes. This means that both males and females have an equal chance of inheriting these genes and showing the trait. The term recessive refers to the way in which the gene is expressed. In the case of albinism, the gene responsible for the condition is a blueprint coding for the production of one of the products needed to make pigment.
If a person carries one gene of a pair that has an altered blueprint and the other of the pair has an unaltered blueprint, then the effects of the altered blueprint do not show. This person is an unaffected carrier. Carriers make enough of the gene product to produce pigment. Therefore, people who carry only one gene responsible for albinism do not know they are carriers. If, however, a person carries two copies of an altered gene, then the product of that gene cannot be made correctly. Such persons have albinism because they cannot produce pigment.
When two people who carriers for the same gene have a child together, then the child has one out of four chances of getting two copies of the albinism gene and having albinism. The child has one out of four chances of getting the two copies of the normal gene and having normal pigment and not being a carrier. The child has two out of four chances of getting one normal gene and one albinism gene and having normal pigment but being a carrier. See Diagram 6.

X-Linked Inheritance
One type of ocular albinism is inherited in X-linked recessive fashion. This type of inheritance is also called “sex-linked”. The term X-linked means that the gene responsible for the disorder is located on the X chromosome. The term recessive means a person can carry one copy of an altered gene (just as in autosomal recessive inheritance) and not show the effects, if she has another unaltered copy.
Since females have two X chromosomes, they will have two copies of all genes on the X chromosome. Males have one X chromosome and one Y chromosome. Because of this difference, males will have only one copy of each gene on the X chromosome. A female can carry one copy of an altered gene on one of her X chromosomes and not show it, because she also carries a second unaltered copy on her other X chromosome. If a male carries one copy of an altered gene on his X chromosome, he does not carry an unaltered copy. As a result, he will show the effects of this gene. See Diagram 7.

If a woman carries the gene responsible for X-linked ocular albinism, the risk for her to give birth to an affected son is 50% or one in two for each birth. None of her daughters will be affected but for each birth of a daughter there is a one in two chance that the daughter will be a carrier.
Children of a man with X-linked ocular albinism will not have ocular albinism, but all of his daughters will be carriers.
These risk figures hold true in each and every pregnancy. They are not changed by the outcome of a previous pregnancy.
Other Reading:
See International Albinism Center website.
Larry, a book for children about a child with albinism going to school, available from the National Association for the Visually Handicapped, 305 East 24 Street, New York City, NY 10010, (212)-889-3141.

NOAH News
, the newsletter of the National Organization of Albinism and Hypopigmentation, 1500 Locust Street, Suite 1816, Philadelphia, PA 19102. NOAH also publishes Information about Albinism bulletins which on various topics related to albinism. Phone 800-473-2310.

The Student with Albinism,
published by NOAH and the National Association for Parents of Visually Impaired, may also be obtained through NOAH, for $3.00 This booklet provides more information on helping the child with albinism to function in the classroom. It was written by Julia Ashley, a PhD student at Nova University who surveyed teachers of students with albinism.
Definitions of Words:
Albinism: A group of inherited conditions which include a decrease in the amount of pigment in the eyes alone, or in both the eyes and skin. The term albino comes from a Portuguese explorer of Africa who saw both dark- and light-skinned natives, and called them “Negroes” (from the word for black) and “Albinos” from the word for white) — he erred in thinking that they were of different races.
Amino Acid: A natural substance found in all living animals and plants. Amino acids are the “building blocks” for protein. When the body takes in protein in food, it breaks the protein down into amino acids, and then uses the amino acids to build other proteins. The body can also change amino acids into certain other substances, including melanin pigment. The term “albino” should be avoided because it calls upon appearance or genetic condition to label a person.
Astigmatism: An eye condition which causes decreased sharpness of vision because the lens does not focus light evenly on the retina so that the image is distorted.
Autosomal: Referring to a chromosome other than one of the sex (X or Y) chromosomes. See “Understanding Genetics.”
B.A.D.S.: Black Locks Albinism Deafness Syndrome: A rare form of albinism which includes a black forelock (an area of the hair at the top of the forehead) and deafness from birth.
Bioptic: A special lens mounted on a pair of glasses to aid low vision.
Braille: A system for writing for the blind that uses characters made up from raised dots which a person can read with his fingertips.
Carrier: A person who has an altered gene but does not show characteristics of it because he or she also has a normal gene. Such a person appears normal but can pass the altered gene on to his or her offspring.
Chediak-Higashi Syndrome: A very rare type of albinism which includes a defect in white blood cells, so that resistance to infection is reduced.
Chromosome: A microscopic structure, made out of DNA, which carries the genes. All cells within the body have a set of chromosomes. The sperm and the ovum contain the chromosomes which parents pass on to their child. During growth both before and after birth the child’s body copies these chromosomes into each new cell. Each chromosome contains a large number of genes.
DNA: Deoxyribonucleic acid, a natural substance which stores genetic information as an intertwined double chain. The body reads the code stored in this chain to learn how to assemble proteins from amino acids.
DOPA: Dihydroxyphenylalanine, a natural chemical which the body makes as a step in the process
of making the pigment melanin.
Enzyme: A specialized protein in the body that helps the body convert one chemical substance to another.
Eumelanin: A darker brown or black form of the pigment melanin. See also “phaeomelanin.”
Fovea: The area of the retina of the eye which contains the nerve fibers which allow the sharpest vision.
Gene: A piece of information, stored in a code in DNA, which tells the body how to make a particular protein. Genes are passed on in the sperm and the egg that combine during conception.
Hairbulb: A “root” of a human hair, from which growth and coloration of the hair develops. Human hairbulbs go through cycles, and when the bulb dies out or is pulled out a new one grows in its place.
Hairbulb pigmentation (incubation) test: A laboratory test in which a hairbulb is incubated in the amino acid tyrosine to see whether or not the hairbulb will make pigment. Also used to test the activity of the enzyme tyrosinase in hairbulbs. This test is not considered to be an accurate measurment of tyrosinase activity and is no longer used.
Hermansky-Pudlak Syndrome: A type of albinism which includes (1) a defect of platelets, which are a small type of blood cell that help the blood clot, and (2) accumulation of a waxy material in various body tissues, sometimes harming the lungs, or intestines. See text for details.
Hypopigmentation: A general term for decreased pigmentation or coloration.
Iris: The colored part of the eye, which closes in and opens out around the pupil, to help screen the amount of light that comes into the eye.
Melanin: A type of pigment or coloring substance made in the eye and skin of humans and many other animals.
Melanocyte: A type of cell specialized to make the pigment melanin. Melanocytes are located in the lower layers of skin and pass pigment up to the higher layers. Melanocytes also are located in the eye and in hairbulbs. Researchers have found melanocytes in the skin, hair and eyes of persons with albinism.
Melanosome: A package of pigment within the melanocyte.
Nevus: A mole or birthmark.
Nystagmus: Involuntary movement of the eyes back and forth.
Phaeomelanin: A yellowish-broth or reddish form of the pigment melanin. Some persons with albinism seem to produce this pigment in areas such as beards. See also “Eumelanin.”
Photochromic: Referring to glasses that change to a darker color (usually gray or orange) when exposed to bright light.
Photophobia: A condition in which bright light makes the eyes particularly uncomfortable.
Pigment: A coloring matter. Pigments block the passage of light and absorb light. The eye sees the light that is not absorbed but reflected back.
Platelet: A small type of white blood cell which helps the blood to clot.
Recessive: Referring to an altered gene which does not show its effect if the person carrying that gene also has an unaltered gene. See “Understanding Genetics.”
Retina: The surface on the inside of the back of the eye. Light enters the eye through the pupil, and the lens focuses the light on the retina. The retina converts the light to a message to the brain.
Transillumination: A test to determine how much light “leaks” through the iris. In a darkened room, a penlight is placed against the side of the eye. Light coming from behind the iris shines out. In persons with albinism, more light shines out because the iris has little pigment, and is translucent.
Tyrosine: An amino acid, or protein building block. Tyrosine comes from a wide variety of foods, and deficiency is rare except in extreme protein malnutrition. The system uses tyrosine to make melanin.
Tyrosinase: An enzyme or specialized protein substance in the pigment cell which promotes the conversion of amino acid tyrosine to DOPA in the process of making pigment.
Ty-Neg: Tyrosinase negative, which refers to a type of albinism in which hairbulbs incubated in a chemical solution of tyrosine do not make pigment. See text for details. Also called Type 1A albinism.
Ty-Pos: Tyrosinase positive, which refers to a type of albinism in which hairbulbs incubated in a chemical solution of tyrosine make pigment. See text for details. Also called Type 2 albinism.
Ultraviolet (UV): a “color” of light not visible to the human eye. Ultraviolet light causes tanning, burning and skin damage.
Yellow Albinism: A type of albinism similar to ty-neg albinism at birth. It is sometimes called “yellow mutant” albinism, though the term “mutant,” which refers to a spontaneous (not inherited) change in genes, is inappropriate. This term is no longer used to classify albinism. See text for details.
X-Linked: Referred to a gene that is passed on with the X chromosome. Females have two X chromosomes, while males have one X chromosome and one Y chromosome. See “Understanding Genetics” for details.
About the Authors
Richard A. King, M.D., Ph.D., Professor of Medicine and in the Institute of Human Genetics at the University of Minnesota, has conducted research on albinism for more than fifteen years, and coordinates the International Albinism Center.
C. Gail Summers, M.D., Associate Professor of Ophthalmology at the University of Minnesota, is involved in research on vision and albinism, and is co-director of the International Albinism Center.
James W. Haefemeyer, M.D., M.S., is a family practice physician in Minneapolis, Minnesota, who has albinism and is a NOAH Scientific Advisor.
Bonnie S. LeRoy, M.S., is a Genetic Counselor at the University of Minnesota.

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