Albinism Health Article

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 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.