Acne: etiology, pathogenesis, types and classification by severity

Pathophysiology of acne

Acne is a chronic, genetically determined disease of the sebaceous glands, which is associated with their increased activity in response to stimulation by androgens (male sex hormones), follicular hyperkeratosis, the activity of microorganisms, the inflammatory reaction of tissues and is manifested by the appearance in areas of the skin with a large number of sebaceous glands of non-inflammatory and inflammatory elements.

This disease is based on one or another degree of inflammation of the sebaceous gland and hair follicle, and the main morphological element is the papulopustule.
The etiology and pathogenesis of acne includes a number of unfavorable factors: dysfunction of the endocrine system, follicular hyperkeratosis, hypertrophy of the sebaceous glands, overproduction and changes in the composition of sebum, activation of saprophytic and opportunistic flora.

A significant role in the development of the disease is played by hereditary predisposition, gastrointestinal pathologies, the presence of foci of chronic infection, the use of certain medications, external use of certain creams and medications, in particular corticosteroids, and irrational cosmetic care.

Let's take a closer look at three mechanisms that occur in the hair follicle and provoke the appearance of such dermatological pathology as acne.

1. Hyperseborrhea (oily skin)

Sebum produced by the sebaceous gland is directly influenced by androgens - male hormones. Puberty is characterized by an increase in the secretion of androgens, which contribute to an increase in sebum production. Hyperseborrhea is a prerequisite for the appearance of acne lesions.

In addition, acne is located in areas of the body that are richest in hair follicles. In 95% of cases, the lesions are located on the face, especially at the level of the T-zone, which is very rich in follicles - the chin, nose and forehead. Lesions can also be found on the back, torso and shoulders, especially in boys, as the density of follicles there is high. This does not necessarily indicate an increase in the level of circulating androgens, which could cause acne, but is more often associated with increased sensitivity of the skin receptors to androgens.

2. Blockage of the follicular canal

In addition to hyperseborrhea, keratinization disorders are observed when the keratinocytes that create the inner surface of the skin-fat follicle divide abnormally quickly. As a result of excessive accumulation of sebum and keratinocytes sticking together, a horny plug is created, which clogs the follicular canal and prevents sebum from reaching the surface of the skin. This accumulation of cells leads to the formation of storage lesions - open comedones (blackheads) and/or closed comedones (whiteheads).

3. Inflammation

From under the horny plug, sebum can no longer be removed, an extremely lipophilic anaerobic environment arises, which creates an ideal environment for Propionibacterium acnes - bacteria naturally present in the hair follicle, which multiply intensively under these conditions.

Continuous sebum secretion creates constant pressure in the follicle, which can rupture. Bacterial antigens spread and come into contact with the dermis, causing inflammation.

The clinical manifestations of these inflammatory lesions are as follows:

• papules (slightly raised skin lesions without pus, pink or red),
• pustules (superficial skin elevations containing pus),
• nodules (round formations more than 5 mm in diameter, palpable under the skin).

Fig. 1 Mechanism of acne development

The exact etiology of the disease remains controversial. The leading role in the pathogenesis of acne belongs to hormonal imbalance and disruption of the normal microbiocenosis of the skin surface, in which opportunistic and transient microflora are activated, in particular, anaerobic gram-positive diphtheroids Propionobacterium acne, which have been in the follicle since puberty.

Clinical manifestations of acne

Clinical manifestations of acne are varied and include non-inflammatory and inflammatory phenomena.

Non-inflammatory type of lesion - closed and open comedones, milia.

Inflammatory type of lesion : the presence of papules and pustules, nodes and deep pustules, characteristic of deep inflammation. Most patients simultaneously exhibit signs of two types of lesions.

Mild acne is characterized by the presence of closed and open comedones or papules with single pustules, which can resolve without therapeutic intervention within 1-2 weeks (Table 1).

Acne of moderate severity is characterized by numerous papules and pustules, deep pustules, more than half of the face area is affected. Numerous pustular papules, comedones are observed, and nodules may be present (Table 1).

In severe cases, the entire face is affected. Numerous pustular papules and comedones, nodules, severe inflammation, and scars are observed (Table 1).

A very severe degree is characterized by an inflammatory stage, in which the entire face is covered with nodules, numerous comedones, pustular papules, nodes are observed, very severe inflammation is present, as well as scars (Table 1).

Table 1 Assessment of the severity of various stages of acne

Modern classifications of acne evaluate acne according to severity and clinical forms. The second, third and fourth stages definitely need the help of a doctor. In the treatment of acne, a cosmetologist should remember that this is a polyetiological disease, therefore, when choosing tactics, it is necessary to take into account the anamnesis, etiology, pathogenesis, and also prescribe consultations with related specialists.

This article is part of the special project "AKNE" .

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