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List of All Topics
Albinism
Introduction
Albinism, a group of inherited disorders, results in little or no production of the pigment melanin. The type and amount of melanin your body produces determines the color of your skin, hair and eyes. Melanin also plays a role in the development of certain optical nerves.
Most types of albinism result in hypopigmentation — either no pigment in your skin, hair and eyes, or lighter pigmentation than would be expected for someone in your family. Because one function of melanin is to absorb ultraviolet light, most people with albinism are sensitive to sun exposure and are at risk of developing skin cancer.
All forms of albinism cause problems with the development and function of your eyes. People with albinism have poor vision that can't be completely corrected with prescription eyewear.
Albinism is present at birth, although some types of the disorder may not be easily identified in infants. Although there's no cure for albinism, people with the disorder can take steps to improve vision and avoid too much sun exposure. Albinism doesn't limit intellectual development or educational potential. Unfortunately, people with albinism often feel socially isolated and experience ridicule or discrimination.
Signs and symptoms
Signs and symptoms of albinism are usually, but not always, apparent in a person's skin, hair and eye color. Regardless of the effect of albinism on appearance, all people with the disorder experience vision impairments.
Skin
Although the most recognizable form of albinism results in milky white skin, skin pigmentation can range from white to nearly the same as parents or siblings without albinism.
For some people with albinism, skin pigmentation never changes. For others, melanin production may begin or increase during childhood and adolescence, resulting in slight changes in pigmentation. With exposure to the sun, some people may develop:
- Freckles.
- Moles, with or without pigment.
- Large freckle-like spots (lentigines).
- The ability to tan.
Hair color can range from very white to brown. People of African or Asian descent who have albinism often have hair color that is yellow, reddish or brown. Hair color may also change by early adulthood.
Eye color
Eye color can range from very light blue to brown and may change with age.
The lack of pigment in the colored part of your eyes (irises) makes them translucent to some degree. This means that the irises can't completely block light from entering the eye. Because of this translucence, very light-colored eyes may appear red in some lighting. This occurs because you're seeing light reflected off the back of the eye and passing out through the iris again — similar to red eye that occurs in a flash photograph.
Vision
Signs and symptoms of albinism related to eye function include:
- Rapid, involuntary back-and-forth movement of the eyes (nystagmus).
- Inability of both eyes to stay directed at the same point or to move in unison (strabismus).
- Extreme nearsightedness or farsightedness.
- Sensitivity to light (photophobia).
The cause of albinism is a mutation in one of several genes. Each of these genes provides the chemically coded instructions for producing one of several proteins involved in the production of melanin. Melanin is produced by cells called melanocytes, which are found in your skin and eyes. A mutation may result in no melanin production at all or a significant decline in the amount of melanin.
In most types of albinism, a person must inherit two copies of a mutated gene — one from each parent — in order to have albinism. If a person has only one copy, then he or she won't have the disorder.
Impact of mutations on eye development
Regardless of which gene mutation is present, the lack of melanin results in abnormal eye development. Vision impairment is, therefore, the common characteristic across all types of albinism.
Melanin plays some yet-to-be-determined role in the development of the retina, the light-sensitive tissue at the back of your eye that transmits signals to your brain. Without enough melanin, a particular area of the retina essential for sharp vision doesn't develop normally.
Melanin also appears to play a role in the development of nerve pathways from your eyes to your brain. In people with albinism, these nerve pathways aren't organized normally.
Types of albinism
The system for classifying types of albinism is based primarily on which mutated gene caused the disorder rather than how it's manifested. Nonetheless, most types of albinism have some features that distinguish them from each other. Types of albinism include:
- Oculocutaneous albinism. Oculocutaneous albinism is caused by a mutation in one of four genes. (5) These mutations result in signs and symptoms related to vision (ocular) and those related to skin (cutaneous), hair and iris color.
Oculocutaneous albinism 1 is caused by a mutation in a gene on chromosome 11. Most people with this type of albinism have milky white skin, white hair and blue eyes at birth. Some people with this disorder never experience changes in pigmentation, but others begin to produce melanin during childhood and adolescence. Their hair may become a golden blond or brown. Their skin usually doesn't change color, but it may tan somewhat. The irises may also change color and lose some of their translucence.
Oculocutaneous albinism 2, caused by a mutation in a gene on chromosome 15, is the most common form of the disorder worldwide. It's more common in Sub-Saharan Africans and African-Americans than in other population groups. In people of African descent, the hair is usually yellow, the eyes are blue-gray or tan, and the skin is white at birth. With sun exposure, the skin may over time develop freckles, moles or lentigines. In some cases, the skin may be light brown, and the hair may be brown, auburn, ginger or red.
In Caucasians with oculocutaneous albinism 2, the hair is usually blond, the skin white and the eyes blue at birth. The hair and eyes may darken. The skin usually develops freckles, moles or lentigines.
The rare oculocutaneous albinism 3, caused by a gene mutation on chromosome 9, has been primarily identified in black South Africans. People with this disorder usually have reddish-brown skin, ginger or reddish hair, and hazel or brown eyes.
Oculocutaneous albinism 4, caused by a gene mutation on chromosome 5, is a rare form of the disorder generally presenting signs and symptoms similar to those of type 2. Studies suggest that this type may be one of the most common forms of albinism among people of Japanese and Korean descent. - X-linked ocular albinism. The cause of X-linked ocular albinism is a gene mutation on the X chromosome. (A woman inherits an X chromosome from each parent. A man inherits an X chromosome from his mother and a Y chromosome from his father.)
In order for a woman to have ocular albinism, she must inherit the gene mutation from both parents. A man with the disorder inherits the gene mutation from his mother. Because there's no corresponding gene on the Y chromosome, the single mutated gene on the X chromosome is sufficient to cause ocular albinism in a man.
People who have ocular albinism have the developmental and functional vision problems of albinism. But a person's skin, hair and eye color are generally in the normal range or slightly lighter for his or her family. - Hermansky-Pudlak syndrome. Hermansky-Pudlak syndrome is a rare albinism disorder caused by one of at least seven mutated genes. People with this disorder have signs and symptoms like those of oculocutaneous albinism, but they also develop lung and bowel diseases and a bleeding disorder.
- Chediak-Higashi syndrome. Chediak-Higashi syndrome is a rare form of albinism caused by a mutation in a gene on chromosome 1. Signs and symptoms are also similar to those of oculocutaneous albinism. The hair is usually brown or blond with a silvery sheen, and the skin is usually creamy white to grayish. People with this syndrome have a defect with white blood cells that results in a susceptibility to infections.
Because albinism is a genetic disorder, interventions to treat people with albinism are limited. Your child will most likely need to wear prescription lenses, which provide modest improvement in vision, and he or she should receive annual examinations by an ophthalmologist.
Although surgery is rarely part of treatment for albinism, your ophthalmologist may recommend surgery on optical muscles that minimizes nystagmus and may provide modest improvement in vision. Surgery to correct strabismus may make the condition less noticeable, but it won't improve vision.
Your doctor will also conduct an annual assessment of your child's skin to screen for skin cancer or lesions that can lead to cancer. Adults with albinism should continue annual eye and skin exams throughout their lives.
People with Hermansky-Pudlak and Chediak-Higashi syndromes usually require regular specialized care to prevent complications and treat them promptly.
Information obtained from National Institute of Health