Everything that gives us individuality, color of eyes, hair and skin tone, exists due to the presence of melanin in cells. Its absence is a genetic pathology of the congenital type. Albinism in humans is not very common, it is inherited from parents, especially if they are both carriers of a recessive mutated gene.
Types and causes of albinism
Synthesis of melanin is due to a special enzyme - tyrosinase. The blockade of its development can lead to an absolute lack of pigment or its deficiency, which provokes albinism.
Methods of inheritance of the disease are divided into autosomal dominant and autosomal recessive type. Depending on the type, the pathology is classified as follows:
- Partial albinism . To make the disease manifest, it is enough to have one parent with a recessive gene.
- Total albinism . Occurs only in the case when both the father and mother have a mutated gene in the DNA.
- Incomplete albinism . It is inherited as autosomal dominant as well as autosomally recessive.
In accordance with clinical manifestations, there is an ophthalmic and an ocular type of pathology. Let's consider in more detail
Eye albinism
This type of disease is outwardly almost invisible. It is characterized by the following symptoms:
- reduced visual acuity;
- strabismus ;
- nystagmus - involuntary movements of the eyeballs.
Skin and hair remain normal or slightly lighter than those of relatives.
It is worth noting that only men are affected by eye albinism, whereas women are only carriers of it.
Oculomotor albinism or HCA
There are three types of considered form of albinism:
- HCA 1. This form is considered with subgroup A (melanin is not produced at all) and B (melanin is produced in insufficient quantity). In the first case, hair and skin are absolutely not pigmented (white), contact with sunlight causes burns, the iris is transparent, the color of the eyes appears red due to translucent blood vessels. The second type is accompanied by a weak pigmentation of the skin, which increases with age, as well as the intensity of hair color, iris;
- HCA 2. The only characteristic feature is white skin irrespective of the race of the patient. Other symptoms are variable - yellow or reddish-yellow hair, light gray or blue eyes, the appearance of freckles in contact areas of the skin with sunlight;
- HCA 3. The most rare type of albinism with inconspicuous manifestations. The skin, as a rule, has a yellowish or rust-brown hue, like hair. Eyes - bluish-brown, and visual acuity remains normal.