Albinism

Albinism is a rare, hereditary (AR) metabolic disorder due to a defect in the enzyme tyrosinase . The disorder results in a partial or complete absence of melanin. It can occur in humans, animals and plants.

Albinism is phenotypically divided into tyrosinase-positive and tyrosinase-negative, genotypically into OCA 1 to OCA 3 .

Biochemical essence[edit | edit source]

Melanin is a pigment synthesized in the melanosomes (derived from the Golgi apparatus) of melanocytes (epidermal cells) from the amino acid tyrosine (see figure). This enzyme has dual activity: tyrosine hydroxylase and dopaoxidase. Under normal circumstances, tyrosine is first hydroxylated by tyrosinase to DOPA – i.e. 3,4-dihydroxyphenylalanine, and then oxidized to dopaquinone. The next enzyme in the sequence catalyzes the tautomerization of the intermediate. The final product subsequently polymerizes into eumelanin.

If there is a defect in the region of the gene encoding tyrosinase (facial protein), the metabolic pathway cannot proceed and the pigment is not synthesized.

OCA 1[edit | edit source]

Mutation of the structural gene for tyrosinase.

OCA 1A (tyrosinase negative) – complete absence of tyrosinase

OCA 1B (yellow albinism - xanthoalbinism) - weak enzyme activity in the hair

OCA 2[edit | edit source]

Mutation of the structural gene for P protein (melanosomal transmembrane protein with a transport function – tyrosine transport), the most common type of albinism.

OCA 3[edit | edit source]

The so-called brown albinism – mutation of the gene for TRP-1 , is known only in blacks Albinism is also often accompanied by phenylketonuria (AR disease, caused by a defect in the enzyme phenylalanine hydroxylase ).

Clinical Picture[edit | edit source]

Total albinism[edit | edit source]

Albinism is manifested by white skin and hair, red or light blue eyes. The skin is very sensitive to UV radiation and at the same time there is a higher risk of developing skin tumors. It also causes faster aging of the skin.

Partial albinism[edit | edit source]

This is partial albinism manifested only locally, for example on areas of the skin and areas of hair. The eyes are not affected in this type.

Links[edit | edit source]

External links[edit | edit source]

Sources[edit | edit source]

ŠTORK, Jiří, et al. Dermatovenerologie. 2. vydání. Praha : Galén, 2013. 502 s. ISBN 978-80-7262-898-8.
MATOUŠ, Bohuslav. Základy lékařské chemie a biochemie. 1. vydání. Praha : Galén, 2010. 540 s.