Albinism: what is it to be albino?

Albinism: what is it to be albino?

Oculocutaneous albinism is a group of hereditary diseases characterized by depigmentation of the skin, hair and eyes. In fact, the presence of melanin pigment in the iris and the retina means that albinism is always accompanied by ophthalmological involvement.

Albinism, what is it?

Definition of albinism

Oculocutaneous albinism is due to a defect in the production of the melanin pigment by the melanocytes, due to a genetic mutation.

The different types of albinism:

Albinism type 1

They result from mutations in the gene for the enzyme tyrosinase which plays a fundamental role in the production of pigment by melanocytes

Albinism type 1A

There is a total abolition of the tyrosinase enzyme activity. Patients therefore have no pigment in the skin, hair and eyes from birth, making them white to white hair with red eyes (the pigment defect in the iris causes the retina to be seen red through)

Albinism type 1B

The decrease in tyrosinase activity is more or less marked. Patients have no pigment in the skin and eyes at birth, making them white with red eyes, but from the first months of life signs of pigment production of varying intensity appear on the skin and iris. (varying from blue to orange-yellow). We speak of yellow mutant or yellow albinism.

Albinism type 2

It is the most common of albinisms, especially in Africa. The responsible gene is the P gene of chromosome 15 playing a role in the transport of tyrosine.

At birth, black children have white skin but blond hair. As the hair grows older, it turns straw-colored and the skin may acquire freckles, dark spots or even moles. The irises are blue or yellow to light brown.

Albinism type 3

It is very rare and only present on black skin. It is linked to mutations in the gene encoding TRP-I: the skin is white, the irises light green-brown and the hair red.

Other rare forms of albinism

Hermansky-Pudlak syndrome

By mutation of a gene on chromosome 10 encoding a lysosome protein. This syndrome associates albinism with coagulation disorders, pulmonary fibrosis, granulomatous colitis, renal failure and cardiomyopathy.

Syndrome de Chediak-Higashi

By mutation of a gene on chromosome 1 encoding a protein involved in the transport of the pigment. This syndrome associates an often moderate depigmentation, hair with a metallic “silvery” gray reflection, and a very increased risk of lymphoma from adolescence.

Griscelli-Pruniéras syndrome

By mutation of a gene on chromosome 15 encoding a protein playing a role in the expulsion of the pigment, it associates moderate skin depigmentation, silver hair and frequent skin, ENT and respiratory infections as well as a risk of blood disease. deadly.

Causes of albinism

Albinism is a hereditary illness by mutation of a gene encoding the production or delivery of the skin pigment by melanocytes. The skin and integuments therefore do not have the possibility of pigmenting properly.

The mode of transmission of this mutation from parent to child is in the majority of cases autosomal recessive, i.e. both parents must be carriers of a gene that is not expressed in them and that these two genes (one paternal, the other maternal) are found in the child.

We all carry two genes, one of which is dominant (which expresses itself) and the other recessive (which does not express itself). If the recessive gene has a mutation, it is therefore not expressed in the person with a dominant gene that is not mutated. On the other hand, during the formation of gametes (spermatozoa in men and ova in women), half of the gametes inherit the mutated gene. If two people conceive a child and are carriers of the mutated recessive gene, then there is a risk that the child will have originated from a sperm carrying the mutated recessive gene and from an egg carrying the same recessive gene. As the child does not have a dominant gene but two mutated recessive genes, he then expresses the disease. This probability is quite low, so there are usually no other cases of albinism in the rest of the family.

Who is most affected?

Albinism can affect Caucasian populations but it is more common in Africa on black skin.

Evolution et complications possible

The main problems caused by albinism are eye and skin. There are no other blood or organ problems except in the very rare Hermansky-Pudlak, Chediak-Higashi and Griscelli-Prunieras syndromes.

Skin risk

White light is made up of several colors “assembled”, which “separate” for example during the formation of a rainbow. A color results from the property that molecules have of absorbing all colors of light except one, for example blue absorbs everything except blue, which is reflected on our retina. Black results from the absorption of all colors. The black pigment of the skin makes it possible to absorb the colors of the light but also and especially the Ultra Violets (UV) which cause a carcinogenic risk for the skin. The absence of pigment resulting from the disease makes patients’ skin “transparent” to UV rays because nothing absorbs them and they can penetrate the skin and damage the cells there, causing a risk of skin cancer.

Children suffering from albinism must therefore avoid any contact of their skin with UV rays by organizing their activities (indoor rather than outdoor sports for example), wearing covering and protective clothing and sun products.

Eye risk

Patients with albinism are not blind, but their visual acuity, near and far, is reduced, sometimes severely, requiring the wearing of corrective lenses, most often tinted to protect the eyes from the sun because they too are deprived of pigment.

From kindergarten, the albino child suffering from a visual deficit is placed as close as possible to the board and is, if possible, assisted by a specialized educator.

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