Oculocutaneous Albinism is a group of hereditary diseases characterized by depigmentation of the skin, hair and eyes. Indeed, the presence of melanin pigment in the iris and the retina make albinism always accompanied by ophthalmological damage.
what is Albinism ?
Definition of Albinism
The oculo-cutaneous albinism is due to a lack of production of the melanic pigment by the melanocytes, because of a genetic mutation.
The different types of albinism:
Albinism type 1
They result from mutations of the tyrosinase enzyme gene that plays a fundamental role in pigment production by melanocytes
Albinism type 1A
There is a total abolition of tyrosinase enzyme activity. Patients therefore have no pigment in their skin, hair and eyes from birth, making them white to white-haired with red eyes (the defect of pigment in the iris makes one see the red retina through)
Albinism type 1B
The diminution of 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, in the first months of life, signs of pigment production of varying intensity appear on the skin and iris (ranging from blue to yellow-orange). We speak of albinism “yellow mutant” or yellow.
Albinism type 2
It is the most common albinism, especially in Africa. The gene responsible is the P gene on chromosome 15, which plays a role in the transport of tyrosine.
At birth, black children have white skin, but blond hair. Growing up, the hair becomes straw color and the skin can acquire some freckles, brown spots or moles. Irises are blue or yellow to light brown.
Albinism type 3
It is very rare and present only on black skin. It is linked to mutations in the gene encoding TRP-I: the skin is white, the irises green-light brown and the red hair.
Other rare forms of albinism
By mutation of a chromosome 10 gene encoding a lysosome protein. This syndrome associates albinism with coagulation disorders, pulmonary fibrosis, granulomatous colitis, renal failure and cardiomyopathy.
By mutation of a chromosome 1 gene encoding a protein involved in the transport of the pigment. This syndrome associates a depigmentation often moderate, hair with metallic silver gray reflection, and a very increased risk of lymphoma as of adolescence.
By mutation of a chromosome 15 gene coding for a protein involved in the expulsion of the pigment, it associates a moderate cutaneous depigmentation, silver hair and cutaneous infections, ENT and respiratory frequent and a risk of blood disease deadly.
Causes of Albinism
Albinism is an inherited disease by gene mutation coding for the production or delivery of skin pigment by melanocytes. The skin and the integuments do not have the possibility of pigmentation properly.
The mode of transmission of this mutation from a parent to the child is in the majority of cases autosomal recessive, that is to say that both parents must carry a gene that is not expressed by they and these two genes (one paternal, the other maternal) are found in the child.
We are all carriers of two genes, one of which is dominant (which expresses itself) and the other recessive (it does not express itself). If the recessive gene has a mutation, it is not expressed in the person with a non-mutated dominant gene. On the other hand, during the formation of gametes (spermatozoa in humans and ovules 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 is derived from a sperm bearing the mutated recessive gene and an egg bearing the same recessive gene. Since the child has no dominant gene but two recessive genes mutated, he then expresses the disease. This probability being rather weak, it does not
Who is the most affected?
Albinism can affect Caucasian populations but is more common in Africa on black skin.
Evolution and possible complications
The main problems caused by albinism are ocular and cutaneous. There are other problems of blood or organs only in the very rare syndromes of Hermansky-Pudlak, Chediak-Higashi and Griscelli-Prunieras.
The cutaneous risk
White light is made up of several “assembled” colors, which “separate” for example during the formation of a rainbow. One color results from the property that molecules have to absorb all the 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 absorbs the colors of the light but also and especially the Ultra Violets (UV) which cause a carcinogenic risk for the skin. The lack of pigment resulting from the disease makes the skin of the patients “transparent” to the UV because nothing absorbs them and they can penetrate the skin and to create damage on the cells, causing a risk of cancer of the skin.
Children suffering from albinism should therefore avoid any contact of their skin with UV by the development of their activities (indoor sports rather than outdoors for example), the wearing of protective and protective clothing and solar products.
Patients with albinism are not blind, but their visual acuity, from near and far, is diminished, sometimes severely, requiring the use of corrective lenses most often tinted to protect the eyes from the sun because they too are devoid of pigment.
From the nursery school, the visually impaired albino child is placed as close as possible to the painting and if possible assisted by a specialized educator.
Symptoms of Albinism
At the level of the skin
In the most severe forms, the diagnosis is usually obvious from birth: the skin is pinkish white, hair and white hairs like snow or even blond.
In less severe forms, the hair is blond and darkens after a few months, gradually becoming light brown in adolescence.
We have seen that the most common forms including “positive Tyrosinase” could appear freckles, brown spots, and moles over childhood.
The skin is very sensitive to UV: in the absence of sun protection, skin cancers appear.
At eye level
In the most severe forms, the irises are bluish gray, translucent, thus appearing red (we see the retina through). Babies do not support light and often have strabismus. Visual acuity is severely impaired.
In less severe forms, the irises are blue, orange-yellow or even light brown. Visual acuity is less diminished.
Albinism is a genetic disease. The only risk factor is therefore inheritance. Mutations are more common in Africa.
The opinion of our doctor
It should be kept in mind that patients with albinism, even if they are often visually impaired, have a perfectly normal physical and intellectual development. It is therefore very important to inform the teaching team from Kindergarten so that the child can attend normal schooling.
In addition, there is sometimes a poor understanding or poor compliance of the entourage during the occurrence of albinism on black skin, because the close family (parents, siblings …), the cousins with whom the child plays have never used to protect themselves from the sun, you have to ask them to play inside with the affected child …
Treatments and care of albinism
There is currently no effective gene therapy for abinism. The only treatment is therefore solar prevention to avoid carcinogenic risk: seek shade and protect the skin and eyes of the sun by the use of covering clothing, hat, glasses and high index sun creams on the skin. discovered areas.
Regular monitoring by a dermatologist and an ophthalmologist is desirable throughout life.