Hypomelanosis is a condition of the skin characterized by a focal decrease in the amount of melanin caused by genetic or some physical (ultraviolet exposure) factors. The main symptom of hypomelanosis is the appearance of hypopigmentation foci of different sizes and intensity on the skin surface, depending on the form of the disease. Diagnosis of this condition is carried out on the basis of the results of physical examination, luminescent and histological examination. In many cases, etiotropic treatment of hypomelanosis is impossible, a variety of local medicinal, physiotherapeutic and cosmetic procedures are used.
General information
Hypomelanosis is one of the variants of leukoderma, in which, for various reasons, the formation of melanin or melanocytes in certain areas of the skin is disrupted. There are many forms of this condition, a large role in its development is played by the genetic characteristics of the organism. Also, in the development of some varieties of hypomelanosis, the provoking role of ultraviolet radiation, local hypothermia, and taking certain medications has been proven. In most cases, skin manifestations are the only symptom of this disease, but sometimes they can be accompanied by signs of dysembriogenesis – damage to the central nervous system, malformations of bones, heart, genitals. The occurrence of hypomelanosis is quite difficult to assess, since often patients do not turn to a dermatologist because of the low severity of symptoms.
Causes
Hypomelanosis of different types may have slightly different mechanisms of development of skin manifestations. However, in general, this condition results from a violation of the formation of melanocytes (most cases of idiopathic hypomelanosis), their increased destruction (with teardrop-shaped hypomelanosis) or migration disorders in the embryonic period (Ito hypomelanosis). As a result, foci with a reduced content of melanocytes in the dermis are formed in certain areas of the skin, which is visually assessed as lightening with smooth and clear contours. The mechanisms that lead to such processes have not been thoroughly studied, in some cases family forms of hypomelanosis have been described (which proves its genetic nature), but external environmental factors, such as ultraviolet radiation, also play a significant role.
Also, hypomelanosis, especially in children, can accompany some other hereditary diseases and conditions. The most common disease of this type is Waanderburg syndrome, in which a focus of hypopigmentation forms on the head and looks like a patch of white skin with light hair above the forehead. Another disease – tumorous scleroderma – is also characterized by hypomelanosis in the form of small foci scattered throughout the body. Sometimes vitiligo is also attributed to one of the forms of the disease, but a number of researchers believe that this is a separate dermatological condition, only superficially similar to hypomelanosis. The main argument in this case boils down to the fact that with vitiligo, the pigment completely disappears from the lesions of the skin, whereas with hypomelanosis, its amount only decreases.
Classification
There are several main types of hypomelanosis, which differ in clinical manifestations, age of onset of the disease, causes and other factors. At the same time, the classification takes into account only those forms of this condition that are independent diseases (with the exception of hypomelanosis Ito), and do not accompany other hereditary and other pathologies. Thus, the following main forms of hypomelanosis are distinguished:
- Teardrop–shaped hypomelanosis is the most common form of this condition. It occurs mainly in women over 30 years of age who have 1-3 skin types – that is, a light shade with a low content of melanin. It has been reliably established that teardrop-shaped hypomelanosis is provoked by prolonged exposure to ultraviolet radiation or sunlight. It is assumed that these factors accelerate the destruction of melanocytes in certain areas of the skin, and their loss is replenished much more slowly, which is why the total number of pigment cells eventually decreases. The relationship between the development of teardrop-shaped hypomelanosis and one of the forms of leukocyte antigen (HLA-DR8) was also found, which may indicate the involvement of immune mechanisms in the development of this condition.
- Hypomelanosis Ito is a genetic disease, mainly of sporadic origin, but hereditary forms are also described. Skin manifestations in this condition look like zigzag or wavy stripes of various sizes and localization. The cause of Ito hypomelanosis is a violation of the process of embryogenesis – migration of melanocyte progenitor cells from the neural tube to future skin tissues in the II-III trimester of pregnancy. At about the same time, the formation of the central nervous system also occurs, which is also disrupted. This leads to the fact that Ito hypomelanosis is accompanied by numerous neurological disorders and other malformations.
- Idiopathic hypomelanosis – in dermatology, it includes almost all forms of this condition with an unclear origin. It is assumed that this is a heterogeneous group of skin pigmentation disorders, the essence of which lies in the violation of one of the stages of migration or differentiation of melanocytes. Sometimes idiopathic teardrop-shaped hypomelanosis is isolated, which is similar in its manifestations to the classical form of the same name, but is caused not by destruction, but by slowing the formation of new melanocytes.
Some dermatologists may distinguish additional forms and varieties of hypomelanosis, but today the above classification is considered generally accepted.
Symptoms
Common to all types of hypomelanosis is the appearance of lighter areas of the skin of various sizes, shapes and localization. If they are located on the skin that has a hairline (head, face in men, groin area), then the hair in these areas also loses pigment and becomes light. Almost all forms of the disease (with the exception of hypomelanosis Ito) are accompanied only by skin manifestations and do not cause other symptoms or organ damage.
Teardrop-shaped hypomelanosis occurs in women aged 30-50 years, who often exposed the skin to prolonged insolation. The first foci of reduced pigmentation occur on the shins in the area of the extensor surface of the knees, they have the shape of circles or ovals with a diameter of up to 1 centimeter. Gradually, foci appear on the forearms and trunk (back, abdomen, chest area), the spread of hypopigmentation to the neck and face with teardrop-shaped hypomelanosis most often does not occur. The spread of foci accelerates when exposed to ultraviolet radiation (in a solarium) and sunlight, in some cases, an increase in the area of skin lesions may be due to metabolic disorders.
Hypomelanosis Ito often occurs in childhood, with an equal degree of probability affects both men and women. Areas of reduced pigmentation in the form of lines and zigzags occur throughout the body in the first weeks and months of life, their size and intensity may vary in different patients. However, as the child grows, their severity gradually decreases, and in adolescence they may disappear altogether. Hypomelanosis Ito is more dangerous for its neurological symptoms – epileptic seizures, mental retardation. Convulsive seizures in this pathology are often persistent and react very poorly to traditional anticonvulsants. Children with Ito hypomelanosis may suffer from autism and motor disinhibition. In addition, numerous malformations of the skeleton and other organs are possible – macrocephaly, curvature of the spine, deformities of the feet, anomalies of the development of the genitals, eyes, teeth.
Idiopathic hypomelanosis is characterized by a significant variety of symptoms, since it can have many mechanisms of development. These may be small rounded spots of the teardrop-shaped type (idiopathic teardrop-shaped hypomelanosis), more extensive foci, areas of hair lightening and much more. The age of development of manifestations of this type of hypopigmentation of the skin is also very variable – from infancy to adulthood. That is why idiopathic hypomelanosis is very difficult to differentiate from other conditions accompanied by loss of skin pigments – partial albinism, vitiligo.
Diagnosis
Diagnosis of hypomelanosis in dermatology is based on the results of examination of the patient, including with the help of a Wood lamp, as well as in controversial cases – histological examination of the tissues of the hypopigmentation site. On examination, foci with a lighter color than the surrounding skin and smooth, clear contours are revealed. The latter is regarded by many dermatologists as a pathognomonic sign of hypomelanosis, unlike other forms of leukoderma. To confirm this, you can make an additional inspection using a Wood lamp with a magnifying glass – in ultraviolet rays, it is much better to see the border between unchanged skin and the focus of reduced pigmentation.
If there is a need for additional histological examination, then a skin biopsy is performed in the focus of hypomelanosis. Microscopic examination will show a decrease in the number of melanocytes relative to the norm. In addition, in some forms of idiopathic hypomelanosis, degradation of the processes of these cells can be noticed. This further aggravates the processes of depigmentation of the skin, which is the cause of the development of the disease. In hypomelanosis, Ito diagnostics also includes an MRI of the brain, an assessment of the main neurological functions. In some cases, focal changes in brain tissue, an increase in the lateral ventricles, and disturbances in the electroencephalogram are detected.
Treatment and prognosis
Etiotropic treatment of hypomelanosis does not exist, basically therapy is reduced to attempts to eliminate pigmented disorders by local means. To do this, intradermal injections of corticosteroids are used (to enhance the activity of melanogenesis) directly into the foci of reduced pigmentation. Similarly, retinoids are used, as well as a drug based on placenta extract. The latter activates the formation of melanocytes due to the high content of biogenic stimulants. However, the effectiveness of all of the above measures varies in different patients, so the prospects for recovery from hypomelanosis are quite ambiguous.
The prognosis of hypomelanosis regarding the patient’s life is favorable (with the exception of severe forms of Ito hypomelanosis), but in terms of recovery it is uncertain. Prevention of the teardrop-shaped form of the disease consists in refusing to abuse sunbathing and visiting a solarium, especially for women with fair skin. In relation to other forms of hypomelanosis, genetic factors and disorders of embryogenesis play an important role, so there is no effective prevention of them.