Albinism in human – People with albinism are often conspicuous for their white skin, white hair and light eyes. The rare hereditary disease means that the body can produce little or no melanin, the skin’s natural pigment. Read more about the topic here: What is the cause of albinism in human? What types are there? And is albinism in human curable?
ICD codes for albinism disease: E70
- What is albinism in human? A genetic metabolic disorder in which the body’s own pigment melanin can only be produced to a limited extent or not at all.
- Frequency : The clinical picture albinism occurs worldwide. It is estimated that one in 20,000 people is affected.
- Symptoms : Light or white skin, hair, and eyes; rarely only the eyes are affected; often associated with visual disturbances, reduced vision, squinting, sensitivity to light and glare.
- Causes : mutation in one or more genes, which means that little or no melanin can be formed.
- Diagnosis : Visual diagnosis in newborns with pronounced symptoms; in case of doubt, dermatological and ophthalmological examination, urine test, genetic test.
- Treatment : There is no cure. However, visual disturbances can be compensated for (e.g. with aids, if necessary surgery for strabismus) and the risk of albinism-related damage can be reduced (consequent UV protection to reduce the risk of skin cancer).
What is albinism in human?
By definition, albinism is the name given to a group of inborn errors of metabolism. Due to genetic defects, the production of the body’s own dark pigment melanin is disturbed in those affected. Normally, melanin is responsible for the color of the skin, hair and eyes.
Thus, in people with albinism, the skin and hair are white, and the eyes are pink or blue-grey. In rarer cases, only the eyes are affected. Then one speaks of ocular albinism.
The term “albus” comes from Latin and means “white”. People with albinism are also called albinos.
However, people with albinism do not only stand out visually. The lack of the pigment melanin has negative effects on the body. For example, those affected are more likely to develop skin cancer because the skin does not tan and burns more quickly in the sun. The eyes can also be damaged more easily as a result of the lack of melanin.
In addition to this “pure” albinism, there is another group of hereditary diseases in which albinism features appear in combination with blood clotting disorders (eg Hermansky-Pudlak syndrome).
Albinism is found around the world and in all ethnic groups. In addition to humans, animals can also be affected.
On average, one in 20,000 people worldwide is an albino, although the frequency varies in different regions of the world. Most cases of albinism occur in Africa: Here the risk of albinism is significantly increased – approximately one in 10,000 people is affected.
Symptoms of albinism in human
The symptoms of albinism can vary in severity – depending on how severely the melanin production is restricted by the genetic defect. Albinism is obvious to some of those affected, but not to others.
Basically, the typical albinism features are above all:
- Very light or completely white skin.
- Very light or white hair (on the head and rest of the body).
- Pale blue-grey or pink eyes (if the iris does not contain any color pigments, the fine blood vessels of the eyeball can shine through – the eyes then appear pink or red).
People with less severe symptoms of albinism have very fair skin and mostly reddish-tinted hair. Their eyes are often blue or brown.
Albinism: eye problems
In addition to the visible symptoms of albinism in human, hereditary disease also manifests itself with other signs. The eyes in particular are often affected. Possible effects of albinism on the eyes include:
- Impaired spatial vision.
- Squinting (strabismus).
- Sensitivity to light and glare (photophobia).
- Ametropia (nearsightedness or farsightedness).
- Uncontrollable, rhythmic shaking of the eye (nystagmus).
The lack of melanin is also responsible for the eye problems in albinism. Namely, the pigment is involved in the development of some anatomical components of the visual complex. Without melanin, the structures do not develop properly.
An example of this is the retina. Without melanin, their development during the embryonic period is disturbed. Therefore, the place of sharpest vision in the eye (fovea centralis) is not properly formed in those affected, which explains the limited vision.
People with albinism can also suffer psychologically. Many experience exclusion and bullying because of their conspicuous and unfamiliar appearance – especially in childhood. This can lead to anxiety disorders, depression and social withdrawal.
Albinism in human: causes and types
The causes of albinism in human are various genetic disorders. The affected genes show a change (mutation) that can also be passed on to offspring. The inheritance for albinism is usually autosomal recessive:
“Autosomal” means that the genes responsible for albinism are located on autosomes (= chromosomes that do not belong to the sex chromosomes). “Recessive” means that the gene mutations in question only appear if a child has inherited this mutation from both the father and the mother.
On the other hand, if a child gets a “healthy” gene copy from one parent and a mutated gene copy from the second parent, it will not develop albinism in human.
This means that not everyone with the potential for albinism will actually develop the disease.
Types of albinism
Depending on the severity of the disease, doctors distinguish between two different types:
- Oculocutaneous albinism : hair, skin, and eyes are involved.
- Ocular albinism : Only the eyes are affected.
A further subdivision of these forms of albinism is possible according to the underlying genetic cause. The formation of the pigment melanin is a complex process in which many different components such as cells, enzymes and proteins are involved. Depending on which building block in melanin production is defective due to a genetic defect, a distinction is made:
Oculocutaneous Albinism Type 1 (OCA1)
In type 1, the erroneous information resides on a gene that contains the information for an enzyme called tyrosinase. This enzyme is important for melanin production. If it is completely missing, the body cannot produce any melanin at all. Those affected have full-blown albinism: the skin is white, the hair is colorless, and the eyes are light blue or pink. Often there is a severe visual impairment. Doctors then also speak of the OCA1A type.
In the weakened variant, the enzyme is present, but only with reduced activity – not enough melanin is formed. The albinism symptoms are then less pronounced. The designation for this subtype is OCA1B.
Oculocutaneous Albinism Type 2 (OCA2)
In this form, the mutation affects a gene that contains the information for a specific membrane protein (P protein) that is responsible for the transport of tyrosinase through the cell membrane. This P protein is not formed correctly as a result of the genetic defect, which then leads to melanin deficiency (type 2 albinism).
How severe the symptoms are in those affected varies. The palette ranges from a barely visible lightening of the skin and hair to complete albinism. Some sufferers develop dark pigment spots on the light skin. Sometimes hair gets darker over time. The visual impairments also vary in severity.
OCA2 is the most common type of albinism worldwide.
Oculocutaneous Albinism Type 3 (OCA3)
It is a rare occurrence of the hereditary disease. The so-called TYRP1 gene is the cause of albinism. This gene stores information for an enzyme that plays an important role in the formation of the pigment melanin.
This type of albinism occurs in black Africans. Those affected have brown or red-brown skin, brown hair, and green-brown or completely brown eyes.
Oculocutaneous Albinism Type 4 (OCA4)
A gene is affected by a mutation that allows the production of transport agents for the proteins of the melanin-forming cells. The symptoms of those affected range from a slight lightening of the skin and hair to complete albinism. Visual impairments can occur and vary in severity.
Oculocutaneous Albinism Type 5 (OCA5)
In 2013, another variant of albinism was first described: OCA5. It was discovered in a family in Pakistan whose members were characterized by fair skin, golden hair and eye symptoms (such as sensitivity to light and glare). The underlying mutation lies at a previously unknown gene locus on chromosome 4 (chromosome band 4q24).
Oculocutaneous Albinism Type 6 (OCA6) and Type 7 (OCA7)
The albinism types OCA6 and OCA7 have also been described for the first time in recent years. The extent of skin and hair pigmentation is very heterogeneous in these forms of albinism. In addition, there may be marked involvement of the eyes.
The cause is a mutation in the SLC24A5 gene (in OCA6) or the C10orf11 gene (in OCA7). These genes contain information for transport proteins. These are involved in the differentiation of the melanin-forming cells.
Types of ocular albinism
There are different types of ocular albinism. The symptoms are limited to the eyes: The iris is very light (light blue or reddish). In addition, visual disturbances occur. Hair and skin are normally colored.
Ocular albinism is usually inherited in an X-linked recessive manner, such as ocular albinism type 1 (Nettleship Falls type). The underlying gene mutation is therefore on the female sex chromosome (X chromosome). Because men basically only have one X chromosome, the gene mutation always has an effect on them.
Women, on the other hand, are mostly symptom-free because they have two X chromosomes. If only one has the relevant gene mutation, the body resorts to the “healthy” gene copy on the second X chromosome. Only in rare cases do women show symptoms of ocular albinism, for example when the “healthy” gene copy is inactivated or when both X chromosomes have the relevant gene mutation.
The autosomal recessive form of ocular albinism is very rare.
Piebaldism (partial albinism)
Piebaldism is a rare congenital pigment disorder. During the embryonic development of those affected, no or hardly any melanocytes form in various skin areas. These are the cells that produce the pigment melanin. This results in clearly delineated areas with little or no pigment.
The light, very light-sensitive pigment spots are mainly found on the forehead, chest, abdomen, upper arms and legs. In addition, those affected have a white forelock and sometimes light or white eyebrows and eyelashes.
The mutation underlying partial albinism is inherited in an autosomal dominant manner. So it is enough that you inherit this mutation from only one parent for this form of albinism to appear.
Diagnosis of albinism in human
In the case of pronounced albinism in human, doctors can already diagnose the newborn based on the strikingly light coloring of the skin and hair.
If visual diagnosis is not sufficient, doctors have various diagnostic methods at their disposal:
- Skin biopsy : The doctor takes a tissue sample (biopsy) and examines the existing melanocytes. He can determine whether they can form melanin or not.
- Urine test : In albinism, the urine may contain higher levels of homogentisic acid – a breakdown product of melanin metabolism.
- Ophthalmologic examination : Babies with albinism often have trouble fixing a spot with their eyes. Children usually learn this within the first two months of life.
- Genetic testing : Genetic testing can detect the mutation and therefore albinism.
A genetic test is recommended for people with albinism who want to have children. The result can be used to assess the risk of inheritance of the metabolic disorder and its possible severity.
Albinism in human: course and consequences
Albinism in human is not yet curable. Those affected must therefore learn to live with the hereditary disease – especially with the increased risk of skin cancer :
The coloring of the skin by melanin is an important protection against the carcinogenic UV rays . The lack of melanin in albinism therefore makes the skin particularly susceptible to sunburn. Just a few minutes of unprotected exposure to the sun leads to burns in those affected. This in turn increases the risk of skin cancer. Skin tumors are therefore a common consequence of albinism.
People with albinism have a normal life expectancy.
Treatment of albinism in human
Those affected are usually interested in one question: Can albinism be treated? The clear answer: albinism is not yet curable. Therefore, the therapy concentrates on preventing consequential damage from the disease on the one hand and on compensating for existing visual disturbances on the other.
Prevention and early detection of consequential damage
Consistent sun protection for fair skin belongs here in order to reduce the risk of skin cancer:
People with albinism should expose their sensitive skin to as little sunlight as possible. They should avoid the sun or wear long clothing, especially around midday and in summer. In addition, the conscientious use of sunscreen with a sufficiently high sun protection factor is advisable.
It is also recommended for people with albinism to see a dermatologist once a year for skin cancer screening . Especially the malignant melanoma (black skin cancer) should be recognized and treated early because of its danger.
Compensation for visual disturbances
Treatment for albinism in human also includes correcting existing visual impairments. Those affected can compensate for reduced eyesight with suitable visual aids (e.g. glasses). Surgery may help against strabismus. People with albinism, who are particularly sensitive to light and glare, can use tinted glasses or contact lenses.