Description of albinism
Albinism is a rare, inherited disease that is characterized by lack of melanin pigment in the body.Pigment is a colored substance that contains cells, and depending on what color pigment has a colored and tissue that contains it. For example, plants are green because they contain the green pigment chlorophyll. Conversely jellyfish body may be completely transparent, because it contains no pigment. The human body contains a pigment called melanin, which has a brown-black color and is found mainly in the skin, hair, fur, and also in the eyes. People whose skin contains more pigment, have darker skin. The main function of melanin is that it prevents the ultraviolet rays contained in sunlight to penetrate deeper into the skin. The skin in fact occur cells called melanocytes, which produce melanin and are introduced it into the skin cells. So melanin accumulates in the surface skin cells, and through him because light can not penetrate fully, forming a kind of curtain. Ultraviolet radiation could otherwise cause damage to skin cells and especially their DNA, causing mutations in the genes and the possible formation of skin tumors. Melanin in the skin is therefore very necessary, as well as hair and fur, which also shields the incident light.
A similar function is performed by melanin in the eye. Eye perceives images through the retina, on which light passing through the cornea, aqueous humor and vitreous pupil. But in order to see in dim light as well as in broad daylight, the amount of incident light is adjusted according to the current environment. This serves iris that expands and contracts, thus changing the pupil size (that is a hole in the middle of the iris). So in broad daylight pupil narrows and released less light than in the dark, when it is the opposite. However iris to light shielding must contain a pigment and it’s just melanin.Different eye color is determined precisely the amount of melanin, which includes the iris. Melanin is also present in the retina, therefore, in its absence are developing retinal.
Albinism is a genetic disease that is inherited in an autosomal recessive frequently. This means that the disease will take effect when it is damaged gene on both chromosomes (Human DNA contains two sets of chromosomes, the chromosomes from one species we always have two, one gets from the mother and one from the father). The gene for the production of melanin is found in a particular place of a chromosome, and if this gene damage only on one chromosome, the individual is then called. “Heterozygote” and the disease is there reflected. However, if the damaged gene on both chromosomes, the individual is called. “Homozygote” and the disease is there reflected. By the time together will be a descendant of a man and a woman, both heterozygotes (will be healthy, but each will have one chromosome affected), the probability that the child will be an albino, will be 25%. Because albinism but it is a rare disease (incidence is about 1:20 000 live births), and the probability that a healthy individual has a damaged gene is very small. However, healthy individuals who are heterozygote (or carriers) can transmit the damaged gene to their offspring and therefore often albinism occurs in certain families. If you have a child together will homozygote and heterozygote, their child will never be an albino, but 50% will again be a carrier. If both parents are albino, their offspring will most likely also albino.
Thus the inheritance works with albinism, and now let’s see what are the risk factors and symptoms.
Risk factors albinism
The risk factor is the presence of the gene affected in the family tree, which is further transmitted, which can be known, so that a member of the family has been vyskytnul albinism.
symptoms of albinism
As already discussed above, with albinism lack melanin. This is expressed by changing the color of the skin, which has a whitish pink color (the surface is shining through the capillary). Hair and hair are white. The eyes have a red color, which is conditioned by the iris also show through the capillaries and larger blood vessels. Therefore, the iris is pink to red.
Other symptoms include reduced visual acuity, as well as twitching of the eyes (nystagmus), squint (strabismus), failure of three-dimensional vision, photophobia (patients avoid direct sunshine). Further, there may be failures field of vision and other visual disturbances.
Albinism occurs in three basic versions.
Generalized (oculocutaneous) Albinism occurs throughout the body suffers, the whole skin, hair and eyes.
Ocular albinism is a form, which are affected only the eyes and the skin and hair have normal color.
Albinism partial (partial) has a different mode of inheritance (autosomal dominant, when just one damaged chromosome to the manifestation of the disease), and manifests itself only at demarcated, variously vast stretches of skin and hair districts. Eyes are not affected.
Not all white spots on the body are but partial albinism. It is necessary to distinguish it from similar units, which are characterized by the loss of pigment in the skin areas. It vitiligo, which is the loss of melanocytes in the skin areas of different causes, and leukoderma, which is lost due to the pigment proběhlého skin inflammation. These units are disproportionately more frequent than the partial albinism, a disorder purely innate and very rare.
Absence of pigments, however, not only present in humans. For example, some plants have white spots on the leaves or annealing, where the white spots do not contain chlorophyll. It is also a failure of pigments. Albinism can be found even among animals, a very common example is the white guinea pigs and mice.
causes of albinism
Albinism cause lies in the failure of melanin production cycle. The enzyme tyrosinase, which is involved in the production of melanin is inoperative and therefore the synthesis (production) of melanin at some point stops. Disorder is caused by mutations in the gene for this enzyme.
But there is a particular type of generalized (oculocutaneous) of the mold when it is not damaged enzyme tyrosinase, but is breached distribution of melanin in the cells (so-called. “Tyrosinpozitivní type”). In this case, the melanin in the melanocytes, although produced, but is unable to be transported into the skin cells.
prevention of albinism
Patients should avoid direct sunlight or use protective equipment (sunglasses, sunscreen with a high factor). This reduces the impairment of eyes and the risk of skin cancer.
treatment with albinism
Therapy exists.
complications albinism
The big complication is eye disorders, such as loss of central vision (central scotoma), impaired visual acuity to blindness. The increased sensitivity of the skin to ultraviolet radiation is also a problem, patients must avoid direct sunlight. Indeed not tan, but burn (tan reaction to sunlight due to increased melanin content in skin cells). The resulting more serious complications are frequent carcinoma (cancer) of the skin. Additionally, there is a premature aging.
