Nature of the Genetic Difficulty


Albinism is caused due to inheritance of recessive alleles (alternative form of gene), either from a single parent (very rare) or from both the parents. There is also a possibility that two non-albinistic parents have an albinistic offspring. In this case, the parents are carriers of albinism gene (the character or trait is not expressed). In rare cases, albinism is caused due to gene mutations. Whatever may be the reason, the presence of the altered gene prevents the body from synthesizing the normal amount of melanin pigment.

albino_african_americans.jpg
African American affected by albinism

In albinism, the melanocytes are present, but genetic mutations interfere with their pigment production or their ability to distribute it to keratinocytes, the major cell type comprising the epidermis, or outer layer of the skin. There are currently five known genetic types of albinism, the most common being oculocutaneous type 1 (OCA1) and type 2 (OCA2). Oculocutaneous means affecting the eyes and skin ("oculo" meaning eye and "cutaneous" meaning skin).

Patients with OCA1 have mutations in a gene called TYR that is responsible for creating the enzyme tyrosinase, used by cells to convert the amino acid tyrosine into pigment molecules that color the skin, hair, and eyes. OCA2, the most common form of albinism in Africa, results from a mutation in the OCA2 gene, which encodes the P protein. We don't know what this P protein does.

TYR gene location
TYR gene location


Basic Facts of Albinism


The growth and development of a person with albinism is the same as that of a normal individual. They also have the ability to reproduce offspring. Hence, it is a misconception that a person with albinism is sterile.

An individual having albinism may express hypomelanism (partial lack of melanin) or amelanism (total lack of melanin) of the skin, hair and eyes.

The eye color of a person with albinism may appear pale blue, red or purple. Since, an albinistic person lacks the photoprotective pigment - melanin, he/she is more susceptible to sunburn. Though lack of melanin increases the risk of skin cancer (if proper care is not taken), it does not cause mortality.

Since the melanin pigment is essential for full development of the retina, an albinistic person usually has eye problems due to abnormal development of retina. Some of the common eye problems are refractive errors (myopia, hypermetropia, astigmatism), photophobia (sensitivity to bright light), nystagmus (rapid movement of eye) and strabismus (misalignment of eye).

According to the phenotypic expression (physical character) of a person with albinism, there are two types viz. oculocutaneous albinism and ocular albinism. In the former case, the person expresses lack of pigment in the eyes, skin and hair; whereas, ocular albinism affects only the eyes and the person has
"The eye color of a person with albinism may appear pale blue, red or purple."
"The eye color of a person with albinism may appear pale blue, red or purple."
normal hair and skin.

Genetic testing is the only diagnostic technique for confirmation of albinism. There are certain treatments for improving the quality of life; however, there is no cure for albinism till date. Since albinism is a hereditary disease, it cannot be transferred from one person to another through dermal contact, blood transfusion or via vector (pathogen carrying organism).

One of the astonishing facts is that not only humans, but plants and animals also suffer from albinism. Like in humans, albinism in plants and animals is caused due the lack of pigment (color). Since albino plants lack the photosynthetic pigment - chlorophyll, they usually have a short life (less than 10 days). In case of animals, albinism is not fatal. However, albino animals may face problems of vision, making it difficult for them to hunt for food and protect themselves from danger. Hence, survival rate of albino animals may be less than a normal animal of the same species.

Prognosis

There is no cure for albinism. Treatment is aimed to ease the symptoms and it depends on the extent of the disorder. Treatment of the eye conditions consists of visual rehabilitation.

Optometrists or ophthalmologists recommend various optical aids. Young children may simply need glasses, and older children can sometimes benefit from bifocal glasses.

The most promising treatment for nystagmus is the eye muscle surgery that reduces the movement of the eyes but vision may not improve in all cases due to other associated eye abnormalities.

For photophobia the eye doctors prescribe dark glasses that shield the eyes from bright light. In case of strabismus, ophthalmologists prefer to treat the infants at the age of six months 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.

It is vital that people with albinism use sunscreen when exposed to sunlight to prevent premature skin aging or skin cancer. Special UV-proof clothing and swimsuits are available and are a good alternative to excessive use of sunscreen.

Sources Cited


http://www.scientificamerican.com/article.cfm?id=killing-albinos-tanzania-albinism

http://www.ncbi.nlm.nih.gov/books/NBK1232/

http://www.buzzle.com/articles/facts-about-albinism.html

http://www.medindia.net/patients/patientinfo/Albinism-Treatment.htm