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Generality
The possible alterations in the color of the skin can be basically divided into two large groups:
- Variations due to increased coloring (hyperpigmentation);
- Discoloration linked to a loss of tone (hypopigmentation).
The underlying causes of skin discolouration can be of various origins and nature: some can be inherited, while others can be acquired over the course of life.
In this article the characteristics of the main types of hyperpigmentation and hypopigmentation involving the skin will be analyzed.
Hyperpigmentation
Skin hyperpigmentation can spread to the entire skin surface, affect more or less large areas or even be limited to single points. In the latter case we speak of focal hyperpigmentation.
Focal hyperpigmentation
When we speak of "focal hyperpigmentation we refer to a" chromatic alteration of the skin that involves only certain and circumscribed points on the skin surface.
Freckles and freckles
Ephelides are brownish spots that become more evident if the individual is exposed to sunlight. In 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 of the eyes and hair).
Freckles in many respects are similar to freckles, from which, however, they differ in a generally darker color and in the fact that they are not affected by solar radiation. Both of these conditions, absolutely harmless, occur at a young age and are more frequent among subjects with fair skin and hair.
Solar and senile lentigo
Solar lentigos are hyperpigmented spots that represent the consequence of "excessive sun exposure. They can occur in men and women of any age, although there is a" greater incidence in individuals over 50 years of age.
Senile lentigos, on the other hand, occur in elderly people as a consequence of skin aging in association with excessive exposure to ultraviolet radiation.
The formation of these hyperpigmented spots is supported by a local overproduction of melanin.
Nevi
The nevi, commonly called moles, are the result of a mass of melanocytes, not sensitive to sunlight as is the case, however, for the solar and senile freckles or lentigos. They can be flat or raised, benign or malignant.
See also: Couperose
Local hyperpigmentation
Skin hyperpigmentation can affect more or less large 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 pregnancy 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, localized at the level of the face.
The problem tends to worsen with sun exposure. The main causative agent is represented by hormonal imbalances that can affect the woman during her life. Considering the photosensitizing action of female sex hormones, melasma can also appear in women who take the birth control pill.
However, it should be noted that melasma is not a purely female skin pigmentation disorder, as it can also occur in men.
In addition to hormonal imbalances, other possible factors involved in the onset of the disorder are represented by genetic factors, stress, exposure to UV rays, endocrine disorders and the intake of some types of drugs.
Generalized hyperpigmentation
Generalized hyperpigmentation, ie extended to the entire skin surface, is characteristic of some pathologies. Among these we remember Addison's disease, an adrenal disease (reduced production of corticosterides), which increases skin pigmentation, until the skin a bronze complexion.
Hypopigmentation
Similar to skin hyperpigmentation, skin hypopigmentation can also be local or generalized.
Local hypopigmentation
Vitiligo is the classic example of local hypopigmentation. It is a rather 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 discolored areas are limited, but over the years they can expand, involving the adjacent areas. In correspondence with these depigmented patches there is an almost total inactivation of the melanocytes (cells responsible for the production of melanin).
The causes of origin are not certain, it is believed that the problem has a psychosomatic nature. In practical terms, stressful conditions (both physical and psychological) can determine the appearance of vitiligo in genetically predisposed subjects. In fact, a certain familiarity with the disease, so much so that the child 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 happens in generalized hyperpigmentation, also in generalized hypopigmentation the skin color changes affect the entire skin surface; however, in this case there is a lack or loss of tone, therefore, the loss of the natural color of the skin. skin.
The best known examples of generalized hypopigmentation are albinism and phenylketonuria.
Albinism
Albinism is a hereditary pathological condition, 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 "hereditary condition. The bodies of people affected by this disease are unable to convert phenylalanine, an essential amino acid, into tyrosine, another essential amino acid for melanin synthesis."
Melanin deficiency manifests itself in widespread skin hypopigmentation.
CONTINUE: Solar radiation "
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