Generality
The possible alterations of the color of the skin can be substantially divided into two large groups:
- Variations due to increased color (hyperpigmentation);
- Dyschromias related to a loss of tone (hypopigmentation).
The underlying causes of skin color changes can be of various origins and nature: some can be inherited, while others can be acquired over a lifetime.
In this article the characteristics of the main types of hyperpigmentation and hypopigmentation involving the skin will be analyzed.
Hyperpigmentation
The hyperpigmentation of the skin can be spread to the entire skin surface, involve more or less extensive areas or even be limited to single points. In the latter case we speak of focal hyperpigmentation.
Focal hyperpigmentation
When we talk about focal hyperpigmentation we refer to a chromatic alteration of the skin that involves only certain and circumscribed points of the skin surface.
Freckles and freckles
Freckles are brownish spots that become more evident if the individual is exposed to sunlight. At the points where the aesthetic defect becomes evident, there is an increased local concentration of melanin (the skin pigment responsible, in fact, for the color of the skin, but also for the eyes and hair).
Freckles in many respects are similar to freckles, from which, however, they differ in a generally darker color and due to the fact that they are not influenced by solar radiation. Both of these absolutely harmless conditions manifest themselves at a young age and are more frequent among subjects with light skin and hair.
Solar and senile lentigo
Solar lentigo are hyper-pigmented spots that are the consequence of excessive sun exposure. They can occur in men and women of any age, although there is a higher incidence in individuals over 50 years of age.
Lentigo senili, on the other hand, occur in elderly people as a result of skin aging in association with excessive exposure to ultraviolet radiation.
The formation of these hyperpigmented spots is supported by a local melanin overproduction.
snows
The snows, commonly called moles, are the result of a mass of melanocytes, not sensitive to sunlight as is the case, on the other hand, with solar and senile lymph nodes. They can be flat or in relief, benign or malignant.
See also: Couperose
Local hyperpigmentation
The hyperpigmentation of the skin can involve more or less extensive areas of the skin surface: in this case we speak of local hyperpigmentation.
The typical example is that of melasma, also known as chloasma or gravidic mask when it occurs in pregnant women. This imperfection, which mainly affects the female sex, is characterized by the appearance of more or less extensive hyperpigmented spots, located at the level of the face.
The problem tends to increase with sun exposure. The main causative agent is represented by the hormonal imbalances that can affect a woman during her life. Considering the photosensitizing action of female sex hormones, melasma can also appear in women taking the contraceptive pill.
However, it is important to point out that melasma is not a disorder of purely female skin pigmentation, since it can also occur in men.
In addition to hormonal imbalances, other possible factors implicated in the onset of the disorder are represented by genetic factors, stress, exposure to UV rays, endocrine disorders and intake of some types of drugs.
Generalized hyperpigmentation
The generalized hyperpigmentation, that is extended to the whole cutaneous surface, is characteristic of some pathologies. These include Addison's disease, an adrenal disease (reduced production of corticosterids), which increases skin pigmentation, to the point of giving the skin a bronze color.
Skin discoloration
Similar to skin hyperpigmentation, hypopigmentation of the skin can also be local or generalized.
Local hypopigmentation
Vitiligo is the classic example of local hypopigmentation. It is a fairly common condition, which consists in the progressive depigmentation of some skin areas such as the hands, the face and the areas around the skin orifices.
The problem tends to worsen over time: at first the bleached areas are limited, but over the years they can expand, involving adjacent areas. In correspondence of these depigmented patches there is an almost total inactivation of the melanocytes (cells responsible for melanin production).
The causes of origin are not certain, it is believed that the problem has a psychosomatic nature. In practical terms, stress conditions (both physical and psychological) can determine the appearance of vitiligo in genetically predisposed individuals. Indeed, a certain familiarity with the disease has been documented, so much so that the son of a parent affected by vitiligo is more likely to be in the same condition.
See also: White spots on the skin
Localized hypopigmentation
Similarly to what occurs in generalized hyperpigmentation, even in generalized hypopigmentation the alterations in the color of the skin affect the entire skin surface; however, in this case there is a lack or loss of tone, hence the loss of the natural color of the skin.
The best known examples of generalized hypopigmentation are albinism and phenylketonuria.
Albinism
Albinism is a pathological condition of hereditary nature, due to a genetic mutation that leads to an amino acid substitution at the level of the tyrosinase enzyme. This protein is an essential cofactor of some reactions that transform tyrosine into melanin.
The absence of the protective role of melanin exposes albinos to a greater risk of developing skin neoplasms.
Phenylketonuria
Phenylketonuria is another pathological condition on a hereditary basis. The organism of people affected by this disease is unable to convert phenylalanine, an essential amino acid, to tyrosine, another fundamental amino acid for melanin synthesis.
Melanin deficiency is manifested by diffuse cutaneous hypopigmentation.
CONTINUE: Solar radiation ยป
