Albinism is the congenital absence of any pigmentation or coloration in an animal, plant, or person, resulting in white hair, feathers, scales and skin and pink eyes in mammals, birds, reptiles, amphibians and fish and invertebrates as well.
Albinism is a congenital disorder characterized in humans by the complete or partial absence of pigment in the skin, hair and eyes.
Albinism is the mutation of the TYR gene, also termed tyrosinase.
This mutation causes the most common form of albinism.
The mutation alters the production of melanin, thereby affecting melanin-related and other dependent traits throughout the organism.
Melanin is a substance made by the body that is used to absorb light and provides coloration to the skin.
Indications of albinism are the absence of color in an organism’s eyes, hair, and skin, due to the lack of melanin.
Some forms of albinism are also known to have symptoms that manifest themselves through rapid-eye movement, light sensitivity, and strabismus.
It affects people of all ethnic backgrounds.
Its frequency worldwide is estimated to be approximately one in 17,000.
Albinism is associated with a number of vision defects, such as photophobia, nystagmus, and amblyopia.
Lack of skin pigmentation makes for more susceptibility to sunburn and skin cancers.
In rare cases such as Chediak-Higashi syndrome, albinism may be associated with deficiencies in the transportation of melanin granules.
This also affects essential granules present in immune cells leading to increased susceptibility to infection.
Albinism results from inheritance of recessive gene alleles.
It is due to absence or defect of tyrosinase, a copper-containing enzyme involved in the production of melanin.
Albinism is considered to be a hereditary condition characterized by the absence of melanin in particular, in the eyes, skin, and hair.
There are two principal types of albinism: oculocutaneous, affecting the eyes, skin and hair, and ocular affecting the eyes only.
There are different types of oculocutaneous albinism.
With ocular albinism, the color of the iris of the eye may vary from blue to green or even brown, and sometimes darkens with age.
Photographs of albinos likely will
demonstrate a “red eye”, due to the red of the retina being visible through the iris.
Because of the lack of pigment in the eyes problems with vision, both related and unrelated to photosensitivity occur.
Patients with albinism are generally healthy, and it does not cause mortality.
The lack of pigment blocking ultraviolet radiation increases the risk of melanomas.
The absence or reduction of melanin in the optical systemâ€™s development may lead to the abnormal crossing of optic nerve fibers, photophobia and decreased visual acuity due to light scattering within the eye, reduced visual acuity due to foveal hypoplasia and possibly light-induced retinal damage.
Eye conditions common in albinism:
Optic nerve hypoplasia
The improper development of the retinal pigment epithelium (RPE), which in normal eyes absorbs most of the reflected sunlight, further increases glare due to light scattering within the eye, resulting in photophobia.
Oculocutaneous albinism results from the inheritance of genetically recessive alleles (genes) passed from both parents of an individual such as OCA1 and OCA2.
Albinism, a mutation that occurs in the OCA1 or OCA2 gene is associated with many types of cancers, other disorders and have impaired vision.
The TRP-1 gene mutation may result in the deregulation of melanocyte tyrosinase enzymes, resulting in a third oculocutaneous albinism (OCA) genotype, “OCA3”.
People can be carriers of genes for albinism without exhibiting any traits, and albinistic offspring can be produced by two non-albinistic parents.
Albinism usually occurs with equal frequency in both sexes.
However, ocular albinism, which it is passed on to offspring through X-linked inheritance, and occurs more frequently in males as they have a single X and Y chromosome, unlike females, whose genetics are characterized by two X chromosomes.
Two different forms of albinism exist: partial lack of the melanin is known as hypomelanism, or hypomelanosis, and the total absence of melanin is known as amelanism or amelanosis.
The enzyme defect responsible for OCA1-type albinism is tyrosine 3-monooxygenase or tyrosinase, which synthesizes melanin from the amino acid tyrosine.
In Nigeria, very few people with albinism appear to survive to old age.
Genetic testing can confirm albinism and what variety it is.
Diagnosis of albinism involves clinical exam of person’s eyes, skin and hairs.
It is managed through lifestyle adjustments: preventing sunburn, visual rehabilitation, surgery on the extra-ocular muscles to decrease strabismus, and nystagmus-damping surgery can also be performed
Glasses, low vision aids, large-print materials, and bright angled reading lights can help.
Photophobia may be ameliorated by the use of
Sunglasses which filter out ultraviolet light can be beneficial.
The abnormal development of the optic nerve can occur as sunlight may damage the retina of the eye as the iris cannot filter out excess light due to a lack of pigmentation.
Some use bioptics, glasses which have small telescopes mounted on, in, or behind their regular lenses.
Its prevalence varies considerably by population, and is highest overall in people of sub-Saharan African descent.
The prevalence of albinism in sub-Saharan Africa is around 1 in 5,000, while in Europe and the US it is 1 in 20,000.
Rates as high as 1 in 1,000 have been reported for some populations in Zimbabwe and other parts of Southern Africa.
Certain ethnic groups and populations have exhibit heightened susceptibility to albinism include: Native American Kuna, Zuni and Hopi nations, Japan, and Ukerewe Island.
Humans with albinism often face social and cultural threats, ridicule, discrimination, or even fear and violence.
Oculocutaneous albinism (OCA) is a set of seven types of genetic mutations which reduce or completely prevent the synthesis of eumelanin or pheomelanin, resulting in reduced pigmentation.
Type I oculocutaneous albinism (OCA1a) is the form most commonly recognized as albino.
It results in a complete absence of melanin in the skin, hair and pink pupils.
Of the seven types recognized most of which do not result in red or pink pupils.
Melanin is an organic pigment that produces most of the color seen in people.
Melanin comes in two color ranges, eumelanin: producing dark browns and blacks and pheomelanin: producing light reddish tans and blondes.
Besides the TYR gene, several other genes can cause albinism.
Other hormones and proteins are involved in melanin production, the presence of which is genetically determined.
All the genetic traits for albinism are recessive traits.
Melanin functions in the normal development of various parts of the eye, including the iris, retina, eye muscles, and optic nerve.
The absence of melanin results in abnormal development of eyes and leads to: problems with focusing, and depth perception.
The eyes of am albino animals appear red because the color of the red blood cells in the retina can be seen through the iris, as it has no pigment to obscure this.
Albinos exposed to intense light typically lose photoreceptors due to apoptosis.
The overwhelming majority of photoreceptors are rods rather than cones, and albinism specifically affects the rod cells, but the number and distribution of the cones is unaffected.
Melanin protects the skin from ultra-violet radiation in sunlight.
Melanosomes block harmful electromagnetic radiation from the sun while allowing beneficial frequencies to enter the body.