Morphologic elements of skin rashes

When assessing the affected skin, the morphology of the rash is established first of all, their prevalence or limitation, localization, symmetry, asymmetry or linearity (for example, along a nerve or vessel), features of mutual arrangement (scattered, grouped, confluent) are analyzed. Monomorphism or polymorphism (true and evolutionary) of the rash is determined. Palpation of the rash, scraping, pressing on the surface with glass (vitropressure, or diascopy) and other additional research methods are used in the diagnosis of dermatoses.

Regardless of the location of changes on the skin, the morphological elements of the skin rash should be carefully analyzed - first primary, then secondary.

Primary rashes are those that appear on previously unchanged skin.

Secondary eruptive elements arise as a result of the evolution of primary ones.

In dermatology, there are six additional pathological conditions of the skin, which in some diseases appear on previously unchanged skin, and in others are the result of the evolution of other elements of skin rashes.

When examining dermatological patients, 23 morphological elements can be identified. Primary rash elements include a spot, blister, nodule, tubercle, node, vesicle, blister, pustule.

A spot (macula) is a change in the color of an area of skin or mucous membrane without changing its relief.

Spots are divided into vascular, pigmented and artificial.

Vascular spots have different shades of red. Their pathomorphological basis is unstable or persistent vascular dilation, excessive formation of the latter and the exit of blood from the vessels. Unstable vascular spots reflect a reflex vascular or inflammatory reaction. With vitropression, they disappear completely (hyperemic spots). Small (up to 2 cm in diameter) vascular spots are called "roseola", larger ones - "erythema". Persistent vascular spots are caused by paretically dilated vessels due to the restructuring of the microcirculatory bed (telangiectasia) or excessive neoplasm of blood vessels (hemangiomas). In cosmetology, the term "couperose" is often used, which means persistent telangiectatic erythema. Vascular spots that occur as a result of the exit of formed elements of the blood from the vessels into the tissue per rhexin or per diapedesim are called hemorrhagic. Fresh spots have a bluish-violet color and do not change during vitropressure. Over time, their color changes to brownish-yellow due to oxidation of hemoglobin (oxyhemoglobin - reduced hemoglobin - biliverdin - bilirubin). Hemorrhagic rashes have a special name - "purpura" (can appear on the skin as petechiae, vibices, ecchymoses).

Pigment spots are associated with an excess of the pigment melanin (hyperpigmented spots) or, conversely, an insufficient amount (absence) of it (hypopigmented and depigmented spots).

Artificial spots are formed by introducing a coloring substance into the skin from the outside, usually various dyes (tattooing, permanent makeup, etc.) or as a result of the deposition of certain coloring metabolic products in the skin (for example, carotenoderma).

A wheal (urtica) is an itchy, non-cavity formation of white or reddish-white color, smooth surface, dense consistency and short-term existence, rising above the skin level. The urticarial element exists from several minutes to several hours (up to 24 hours) and resolves without a trace. The mechanism of wheal formation is localized edema of the papillary layer of the dermis, which occurs due to acutely developing expansion and simultaneous increase in the permeability of blood vessels, when exposed to a number of biologically active substances (histamine, serotonin, acetylcholine, etc.). Most often occurs with urticaria and reflects an allergic reaction of the reaginic or immune complex type. In the case of development of diffuse edema of the subcutaneous tissue, a giant wheal (angioedema, or Quincke's edema) occurs.

A nodule, papule, is a non-cavity formation of varying density, inflammatory or non-inflammatory origin, that rises above the skin level.

Papules can form as a result of proliferation in the epidermis (acanthosis, hypergranulosis), infiltration in the dermis (lymphocytes, histiocytes, mast cells, etc.), proliferation of various structures in the dermis (vessels, secretory sections and excretory ducts of glands, etc.), deposition of metabolic products (lipids, mucin, amyloid, calcium, etc.).

Papules can be inflammatory and non-inflammatory. Nodules reflecting the inflammatory process are colored in various shades of red. Non-inflammatory elements can have the color of normal skin or be pigmented. According to shape, there are flat (epidermal and epidermodermal), hemispherical (dermal) and pointed (follicular) papules.

By size, papules are classified as: miliary (the size of a millet grain - up to 2 mm in diameter), lenticular (the size of a lentil - about 5-7 mm in diameter), nummular (the size of a coin - about 2-3 cm in diameter) and plaques (5 cm or more in diameter).

A tubercle (tuberculum) is a limited, cavity-free element from 2 to 7 mm in diameter, rising as a result of the formation of a chronic inflammatory infiltrate (granuloma) in the dermis. The mechanism of tubercle formation is productive granulomatous inflammation in the dermis. It occurs in some rare dermatoses (tuberculosis, tertiary syphilis, leprosy, sarcoidosis, etc.). At the onset, the tubercle has a great resemblance to an inflammatory papule. The color varies from reddish-brown to bluish-red, its consistency is dense or soft. Tubercles usually occur on limited areas of the skin, group together and can merge. Unlike a papule, a tubercle always leaves a scar (after ulceration) or cicatricial atrophy (without ulceration) upon its resolution.

A node is a large, non-angular formation of varying density, inflammatory or non-inflammatory in nature, located in the subcutaneous fat tissue and in the deep layers of the dermis.

Nodes can be inflammatory and non-inflammatory. Inflammatory nodes are colored red in various shades. They can rise above the skin or be located in its thickness. Nodes reflecting acute inflammation have unclear contours, a doughy consistency (for example, a furuncle). On the contrary, nodes representing chronic inflammation or a tumor are distinguished by varying degrees of density, clarity of boundaries. Nodes representing a clinical reflection of specific inflammation (in tuberculosis, tertiary syphilis - gumma, leprosy, sarcoidosis) or a malignant tumor can undergo disintegration

A vesicle (vescula) is a raised, cystic formation in the epidermis, 1 to 5-10 mm in size, containing serous fluid.

The cavity during the formation of a vesicle is always intraepidermal, sometimes multi-chambered. The mechanisms of vesicle formation are vacuolar dystrophy (intracellular edema), spongiosis (intercellular edema), ballooning dystrophy (a sign of damage to epithelial cells by herpes viruses).

A bladder (bulla, pemphig) is a raised, cystic formation, larger than 10 mm, containing serous or serous-hemorrhagic fluid.

The shape and size of the blister may vary, the cavity is single-chambered. The cavity may be located intraepidermally (subcorneal and suprabasal) and subepidermally. The cavity of the blister occurs only under the condition of preliminary damage to the epidermal cells, disruption of the connections between them or between the epidermis and the dermis. The causes of these damages may be exogenous and endogenous. Exogenous factors include obligatory physical factors (friction, high temperature), as well as chemical factors (obligatory concentrations of acids and alkalis) and biological factors (microbes). Endogenous factors are immune complexes that have an immunopathological effect on the desmosomes of epidermocytes (acantholysis in pemphigus), the basement membrane (epidermolysis in bullous pemphigoid) or on the connective tissue of the papillary tips (Duhring's dermatosis).

A pustule is a raised, cystic formation, 1 to 10 mm in size, containing pus.

A pustule is always a cavity inside the epidermis, sometimes under it. This primary cavity eruption element is formed as a result of necrosis of epidermal cells with the formation of a purulent cavity. The formation of a pustule is preceded by damage to keratinocytes by the products of the vital activity of pyogenic microbes (exogenous factors of an infectious nature) and enzymes of neutrophilic granulocytes. In some dermatoses, the formation of a pustule is caused by the action of well-studied endogenous factors of a non-infectious nature, called "microbial pustular dermatoses".

It should also be emphasized that after establishing the type of primary element of the rash, histological examination of the skin is of great importance for verifying the diagnosis of dermatosis.

Secondary morphological elements of skin rashes include secondary spots, erosions, ulcers, scars, scales, crusts, cracks, and abrasions. Their significance for retrospective diagnostics of dermatoses is not the same.

A secondary spot (macula) is a local change in skin color at the site of a previous rash.

The secondary spot may be hyperpigmented, which is often due to the deposition of hemosiderin and, less often, melanin, and hypopigmented due to a decrease in the amount of melanin due to a temporary disruption in the function of melanocytes that are in the area of the pathological focus.

Erosion (erosio) is a superficial skin defect within the epidermis.

Erosion occurs more often as a result of opening of intraepidermal cavity formations, less often as a result of disruption of epidermal trophism due to a pathological process in the dermis (for example, erosive syphiloma). The erosive defect is completely epithelialized without formation of a scar.

An ulcer (ulcus) is a deep defect in the dermis or underlying tissues.

An ulcer occurs as a result of the disintegration of a pathologically altered focus of purulent-necrotic inflammation, ischemia (trophic ulcer), infectious granuloma, malignant tumor (in this it differs from a wound, which occurs due to an exogenous violation of the integrity of the skin layers). During evolution, a scar is formed at the site of the ulcer, which often repeats its shape.

A scar (cicatrix) is newly formed connective tissue at the site of damaged skin and deeper tissues.

There is no skin pattern in the area of the scar, a decrease in the amount or absence of hair is noted. There are normotrophic, hypertrophic, atrophic and keloid scars. A normotrophic scar is located at the skin level, a hypertrophic scar protrudes above it, and an atrophic scar is located below the skin level. Keloid scars are classified as pathological scars, they protrude above the skin level and are characterized by active peripheral growth, especially after their excision, and subjective sensations (itching, paresthesia). If connective tissue forms at the site of the pathological scar without prior damage to the integrity of the skin, then this process is called cicatricial atrophy.

A scale (squama) is a conglomerate of loosened horny plates.

Normally, there is constant desquamation of the epithelium, but this process is invisible to the naked eye (physiological peeling). The mechanisms of scale formation are parakeratosis (the presence of cells with nuclei in the stratum corneum) and hyperkeratosis (thickening of the stratum corneum). Parakeratotic peeling is a characteristic post-peeling reaction of the skin.

Depending on the size and type of scales, a distinction is made between flour-like (resembles the dispersion of “flour”), pityriasis-like or pityriasis-like (resembles the dispersion of “bran”), lamellar (large and small lamellar) and exfoliative (in large layers) peeling.

The crust is a dried exudate.

The color of the crusts can be used to judge the origin of the exudate: serous exudate dries into crusts of a honey-yellow color, purulent - greenish-gray, hemorrhagic - brownish-black. In some cases, scaly crusts are diagnosed, i.e. scales soaked with exudate. Crusts often form after the regression of cystic elements (vesicles, blisters, pustules) and on ulcers.

A fissure (fissura, rnagas) is a linear skin defect associated with a violation of its elasticity.

Causes of cracks include decreased sebum production (dry skin), maceration (swelling of the stratum corneum in a humid environment), keratosis (thickening of the stratum corneum) and infiltration in the dermis. The crack can be superficial (within the epidermis) or deep (penetrating into the dermis).

An abrasion (excoriatio) is the result of mechanical trauma to the skin when scratching it.

It is a consequence of itching. Excoriations have a linear, comma-shaped or triangular shape. Clinically, they are white stripes of loosened horny layer, or erosions covered with hemorrhagic crusts, located dotted, or continuous linear erosions covered with hemorrhagic crusts.

Scab (eschara) - limited dry necrosis of the skin, black or grayish in color, spreading to varying depths and firmly connected to the underlying tissues

It may occur as a result of exposure of the skin surface to obligatory factors of a physical or chemical nature (high temperature, concentrated acids, for example, during deep peeling, alkalis, etc.) or as a result of impaired microcirculation in the area directly adjacent to the lesion.

Pathological conditions of the skin include keratosis, lichenification, vegetation, dermatosclerosis, anetoderma and atrophoderma.

Keratosis is a build-up of dense, dry, hard-to-remove horny masses of a waxy yellow or grayish color.

Lichenification (Lichenificafio) is characterized by a pronounced skin pattern, its thickening, dryness and brownish-bluish color, often peeling.

Vegetation (vegetatio) - a formation raised above the skin (mucous membranes) in the form of a "comb". The surface of the vegetation can be dry, with a normal or thickened stratum corneum, as well as wet and eroded (in folds).

Dermatosclerosis is an area of skin compaction with decreased mobility in relation to the underlying tissues. The skin does not fold, and when pressed with a finger, no impression remains.

Anetoderma (anetodermia) - small areas of atrophy of the skin itself (dermis) of a whitish color with a wrinkled or slightly hernia-like protruding surface. When pressing on these areas with a button probe, the latter easily "falls" into the skin - a symptom of a "bell button", as if into a void (Greek anetos - empty).

Atrophoderma (alrophodermia) - varying depth of skin depression or brownish color over areas of atrophy of subcutaneous fat tissue. The skin pattern is not changed. In cosmetology, secondary atrophoderma is encountered, which is residual phenomena at the site of resolved inflammatory nodes in places of intramuscular injections or after liposuction (lipoaspiration), as its complication.

An objective examination of the patient is carried out according to generally accepted rules and includes both clinical and other research methods (laboratory, instrumental). In addition, special laboratory examination methods (for example, cytological, immunological) are used in the diagnosis and differential diagnosis of some dermatoses. Dermatocosmetologists also widely use additional invasive methods for assessing the condition of the skin

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