Introduction
Pigment disorders of the skin (medically called pigment nevi) are benign changes that can be clearly distinguished and distinguished from the surrounding skin in color. Almost everyone has a pigment disorder of the skin at some point on his or her body, but this has no disease value. Colloquially, terms such as “mole” or “birthmark” are often used to describe such pigment disorders.
There are different types of pigment disorders, which can each be divided into different subgroups. There are certain cells in the skin that are responsible for how dark our skin is. These cells are called melanocytes and produce melanin.
The melanin produced absorbs UV radiation and protects other cells from it. The melanin also gives the human skin its characteristic color. Depending on the type of pigment disorder, different causes can be the reason for a pigment disorder of the skin.
In most cases, however, the melanocytes and the melanin produced play an important role in explaining the symptoms. Another important cell group to explain a number of pigment disorders are the so-called nevus cells. These are very similar to melanocytes and share with them the ability to produce melanin, just like melanocytes.
Classification
In general, one can distinguish hyperpigmentation (overpigmentation) from hypopigmentation (underpigmentation). Depending on whether there are too many or too few melanocytes or melanin in the skin. In albinism, for example, a form of hypopigmentation, there is hardly any melanin in the skin, which is why the people affected have extremely light skin, hair and eyes.
In order to classify the various pigment disorders and divide them into specific groups, one uses the different layers of the skin. The skin consists roughly of three layers (from the outside to the inside): The pigment disorders are also classified according to whether they originate from melanocytes or nevus cells. Both cell types are responsible for the formation of melanin in the layers and for the pigmentation of the skin.
In the group of pigment disorders that originate from melanocytes, it is therefore still possible to distinguish whether they occur in the epidermis or in the dermis. The pigment disorders of the nevus cell group are not further subdivided. In the fourth group, pigment disorders are recorded which originate from atypical melanocytes or nevus cells.
Pigmentary disorders such as the changes colloquially called moles, freckles, or café-au-lait spots can be classified in the group of pigmentary disorders caused by melanocytes occurring in the epidermis. Other forms of pigmentation disorders are usually not known in the population, which is why changes that should actually be classified in other groups are erroneously called moles or similar.
- Epidermis,
- Dermis,
- Subcutis.
