Albinism

Albinism (oculocutaneous albinism) is a hereditary defect in melanin production, resulting in widespread hypopigmentation of the skin, hair and eyes; melanin deficiency (and hence depigmentation) may be complete or partial, but all areas of the skin are affected. Eye involvement causes strabismus, nystagmus and visual impairment. Diagnosis is usually obvious, but an eye examination is necessary. There is no effective treatment other than protecting the skin from sunlight.

There are 2 forms of albinism: oculocutaneous and ocular. The oculocutaneous form can be tyrosine negative or tyrosine positive and is inherited in an autosomal recessive manner linked to the X chromosome.

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Oculocutaneous albinism

Tyrosine negative albinism

These albinos do not produce melanin, which results in light hair and very pale skin.

The iris is transparent, transillumination, a symptom of "pink" eyes.

Fundus of the eye

• Lack of pigment with suspiciously large choroidal vessels.
• Hypoplasia of the vessels of the perimacular arcades.
• Hypoplasia of the fovea and optic nerve.
• Refractive errors, visual acuity <6/60.

Nystagmus is usually pendulum-shaped horizontal, increasing in bright light. The amplitude decreases with age.

Chiasma with decreased number of crossing fibers. Pathology of the visual pathways: from the lateral geniculate body to the visual cortex.

Tyrosinase-positive albinism

In this form of albinism, varying amounts of melanin are synthesized, and hair and skin color can range from very light to normal.

• The iris is blue or dark brown, transillumination.
• The fundus of the eye shows varying degrees of hypopigmentation.
• Visual acuity is reduced due to foveal hypoplasia.

Associated syndromes

• Cbediak-Higashi syndrome is a white blood cell abnormality characterized by recurrent purulent infections and early death.
• Hermansky-Pudlak syndrome is a lysosomal storage disease of the reticuloendothelial system, characterized by a tendency to hematomas due to platelet dysfunction.

Ocular albinism

Ocular albinism is characterized by predominantly eye involvement, with less noticeable changes in skin and hair color.

The type of inheritance of ocular albinism is X-linked, less commonly autosomal recessive.

Female carriers are asymptomatic, with normal vision, partial transillumination of the iris, and a finely dispersed zone of depigmentation and pigment granularity at the midperiphery. Male patients have hypopigmented irises and fundi.

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Forms of albinism

Oculocutaneous albinism is a group of rare hereditary disorders in which melanocytes do not produce melanin or produce it in insufficient quantities, resulting in eye and skin pathologies. Ocular albinism is a decrease in retinal pigmentation, strabismus, nystagmus, decreased visual acuity, monocular vision. These disorders arise as a result of pathology of the visual tract of the central nervous system. Ocular albinism can occur in addition to skin lesions.

There are four main genetic forms of albinism, which have a variety of phenotypes. All forms are autosomal recessive.

Type I is caused by the absence (type IA; 40% of all cases) or insufficient amounts (type IB) of tyrosinase. Tyrosinase catalyzes several steps in the synthesis of melanin.

Type IA - classic tyrosinase-negative albinism: skin and hair are milky white, eyes are blue-gray.

Type IB - pigmentation disorder may be pronounced or slightly noticeable.

Type II (50% of all cases) is due to a mutation in the P gene. The function of the P protein is not yet understood. The range of pigmentation disorder phenotypes varies from minimal to moderate. With sun exposure, pigmented nevi and lentigines may form, which may enlarge and darken.

Type III is found only in black patients. It is caused by mutations in the tyrosinase-related protein gene, which is responsible for the synthesis of melanin. The skin is brown, the hair is red.

Type IV is an extremely rare form in which the genetic defect is in the gene that codes for protein transport.

In the group of hereditary diseases, oculocutaneous albinism is accompanied by increased bleeding. In Chediak-Higashi syndrome, the number of platelets decreases, resulting in hemorrhagic diathesis. Patients develop an immunodeficiency state due to a violation of the granularity and structure of leukocytes. Progressive neurological degeneration develops.

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How to recognize albinism?

The diagnosis of all types of albinism is obvious from examination of the skin, but it is necessary to ensure that the iris is translucent, the pigmentation of the retina is reduced, visual acuity is reduced, and eye movement disorders (strabismus and nystagmus) are present.

Treatment of albinism

There is no treatment for albinism. Patients are at risk of developing skin cancer and should avoid sunlight, wear sunglasses with UV filtering and use sunscreen with SPF> 30