Albinism

Definition

Definition of Albinism
Albinism is a congenital disorder characterized by the complete or partial absence of pigment in the skin, hair and eyes due to absence or defect of an enzyme involved in the production of melanin. Albinism results from inheritance of recessive gene alleles and is known to affect all vertebrates, including humans. While an organism with complete absence of melanin is called an albino (play), an organism with only a diminished amount of melanin is described as albinoid.

Symptoms

Symptoms of Albinism
In humans, there are two principal types of albinism, oculocutaneous, affecting the eyes, skin and hair, and ocular affecting the eyes only.

Most oculocutaenous albinistic humans appear white or very pale as the melanin pigments responsible for brown, black, and some yellow colorations are not present. Ocular albinism results in pale blue eyes, and may require genetic testing to diagnose.

Because individuals with albinism have skin that partially or entirely lacks the dark pigment melanin, which helps protect the skin from the sun's ultraviolet radiation, their skin can burn more easily from overexposure.

Causes

Causes of Albinism
Most forms of albinism are the result of the biological inheritance of genetically recessive alleles (genes) passed from both parents of an individual, though some rare forms are inherited from only one parent. There are other genetic mutations which are proven to be associated with albinism. All alterations, however, lead to changes in melanin production in the body.

The chance of offspring with albinism resulting from the pairing of an organism with albinism and one without albinism is low. However, because organisms can be carriers of genes for albinism without exhibiting any traits, albinistic offspring can be produced by two non-albinistic parents. Albinism usually occurs with equal frequency in both sexes. An exception to this is ocular albinism, which it is passed on to offspring through X-linked inheritance. Thus, ocular albinism occurs more frequently in males as they have a single X and Y chromosome, unlike females, whose genetics are characterized by two X chromosomes.

Diagnosis

Diagnosis of Albinism
Genetic testing can confirm albinism and what variety it is, but offers no medical benefits except in the cases of non-OCA disorders (see below) that cause albinism along with other medical problems which may be treatable. The symptoms of albinism can be treated by various methods detailed below.

Treatment

Treatment of Albinism
For the most part, treatment of the eye conditions consists of visual rehabilitation. Surgery is possible on the ocular muscles to decrease nystagmus, strabismus and common refractive errors like astigmatism. Nystagmus-damping surgery can also be performed, to reduce the "shaking" of the eyes back and forth. The effectiveness of all these procedures varies greatly and depends on individual circumstances.

Glasses and other vision aids, large-print materials as well as bright but angled reading lights, can help individuals with albinism, even though their vision cannot be corrected completely. Some people with Albinism do well using bifocals (with a strong reading lens), prescription reading glasses, and/or hand-held devices such as magnifiers or monoculars. Contact lenses may be colored to block light transmission through the iris. But in case of nystagmus this is not possible, due to the irritation that is caused by the movement of the eyes. Some use bioptics, glasses which have small telescopes mounted on, in, or behind their regular lenses, so that they can look through either the regular lens or the telescope. Newer designs of bioptics use smaller light-weight lenses. Some US states allow the use of bioptic telescopes for driving motor vehicles. (See also NOAH bulletin "Low Vision Aids".)

Prognosis

Prognosis of Albinism
Albinism does not usually affect lifespan. Hermansky-Pudlak syndrome can, however, shorten lifespan due to lung disease or bleeding problems.

Prevention

Prevention of Albinism
Because albinism is inherited, genetic counseling is important. People with a family history of albinism or hypopigmentation should consider genetic counseling.