Eczematous skin reaction (eczema): causes, symptoms, diagnosis, treatment

Among various dermatoses, the eczematous reaction is one of the most common. It is an intolerant reaction to various stimuli. It can be caused by many factors of both endogenous and exogenous nature, leading to damage to the epidermis. Localized foci of damaged epidermis lead to a local increase in osmotic pressure, accompanied by increased movement of tissue fluid from the dermis to the epidermis, leading to the formation of vesicles in it, and when it moves to the surface - to the formation of so-called serous wells.

Clinically, this reaction is characterized by predominantly erythemato-vesicular manifestations in the acute period, and in the chronic course, polymorphism is expressed due to nodules, erosions, and scaly crusts. The main element of this reaction is the spongiotic vesicle.

The eczematous reaction is based on immune disorders similar to those in allergic contact dermatitis. Most often, the eczematous reaction is a consequence of the antigen-antibody reaction. Immunocompetent T-lymphocytes secrete mediators (lymphokines) as a result of exposure to the corresponding antigens, and transformed lymphocytes secrete a macrophage inhibitory factor and a free histamine cytotoxic factor, which leads to corresponding changes in the epidermis. A.A. Kubanova (1985) attaches great importance to prostaglandins of group E in the development of allergic reactions in patients with eczema, which are closely related to the formation of cAMP, which inhibits the release of mediators of allergic reactions (histamine, etc.). According to the author, increased synthesis of prostaglandins and disorders in the adenylate cyclase system lead to the development of an inflammatory reaction of the skin and are one of the links that determine the development of immune disorders and an increase in allergic reactivity.

Pathomorphology of eczematous skin reaction (eczema). With an eczematous reaction, regardless of its type, the histological picture is uniform and changes only depending on the severity of the process.

In acute eczematous reactions, the dynamics of the process are characterized by several successive clinical and morphological phases.

The erythematous phase is characterized by reddening of the skin in one or more places. Histologically, edema of the upper half of the dermis, limited, mainly lymphocytic infiltrates and dilation of the vessels of the papillary dermis are observed.

In the papular or papulovesicular phase, nodules appear on an erythematous base with a diameter of up to 1 mm, on the surface of which vesicles quickly form. Histologically, in addition to edema and lymphocytic infiltrates in the dermis, spongiosis, acanthosis with elongation of epidermal outgrowths, parakeratosis and slight vesiculation are detected.

In the vesiculation phase, which is most characteristic of this reaction, significant spongiosis with widening of intercellular spaces, destruction of desmosomes and formation of blisters of various sizes containing lymphocytes and serous fluid are observed in the vesicle zone. Subcorneal blisters also appear. If the process is complicated by pustulization, the blisters transform into pustules filled with a large number of granulocytes. In the epidermis, there is pronounced acanthosis and exocytosis, and a significant number of eosinophilic granulocytes appear in the perivascular infiltrates of the dermis.

The formation of crusts is associated with the drying of serous exudate on the surface of the epidermis. They are penetrated by disintegrated neutrophilic granulocytes and epithelial cells, while in the dermis edema and infiltration are less pronounced.

The squamous phase is characterized by epithelialization of the lesions and rejection of scales and scaly crusts. Histological examination reveals acanthosis and parakeratosis with exfoliation of the stratum corneum, slight edema of the upper dermis.

Electron microscopic examination of the skin in the acute period of this reaction revealed intracellular edema with the formation of vacuoles of various sizes in the cytoplasm of epithelial cells located around the nucleus (perinuclear edema). The nuclei are in various stages of edematous dystrophy, often with liquefaction of large areas of the karyoplasm. The tonofilaments are sharply swollen, homogeneous, and have no clear boundaries: mitochondria, cytoplasmic reticulum, and Godgi apparatus are not determined. Keratohyalin lumps are not visible in the granular layer, indicating severe hypoxia of the epithelial cells. With increasing edema, vacuoles appear not only near the nucleus, but also on the periphery of the cytoplasm of the epithelial cells. In the dermo-epidermal zone, a rupture of the dense plate is noted, through which fluid and formed elements of the blood move from the dermis into the epidermis. In the dermis, the venous plexus of the papillary layer is primarily involved in the process, participating in the formation of severe edema of these parts of the dermis. Hypertrophy of endotheliocytes without pronounced cell necrosis and a sharp narrowing of the lumens are detected in the vessels. When studying the morphology of the perivascular infiltrate cells, it was shown that inflammatory cells consist mainly of B-lymphocytes.

The chronic stage of the eczematous process may develop as a continuation of the acute or subacute stage as a result of constant exposure to an irritant for a long time. The foci of chronic eczema have a characteristic livid-red color. Skin infiltration, increased relief, a tendency to cracking and peeling are noted. Histologically, vasodilation is observed in the upper half of the dermis, perivascular infiltrates consisting of histiocytes with an admixture of a small number of lymphocytes; edema, as a rule, is weakly expressed. In the epidermis - acanthosis, massive hyperkeratosis, in places multi-row basal skin, sometimes parakeratosis. Electron microscopy in this phase revealed a decrease in edema, although the structure of desmosomes remains disrupted. A large number of ribosomes, many large mitochondria with dystrophic changes in them were found in the cytoplasm of epithelial cells.

R. Jones (1983), as a result of an ultrastructural study of the skin at various stages of the process, showed that early changes always begin with the dermis, or more precisely with its vascular apparatus, accompanied by a sharp swelling of the papillae, from which the edematous fluid is eliminated into the epidermis through the dermoepidermal membrane, then intracellular edema appears in the form of vacuolization of epithelial cells with subsequent rupture of their membranes and cell death with the formation of spongiotic vesicles.

Histogenesis of eczematous skin reaction (eczema). Humoral immune factors play a significant role in the development of eczematous reactions. Having conducted a quantitative study of immune-competent cells of the peripheral blood (T- and B-lymphocytes), V.L. Loseva (1981) showed that the number of T-lymphocytes is slightly increased in patients with various forms of eczema. When studying the infiltrate of the dermis, it turned out that the basis of the infiltrate is immune lymphocytes and degranulated tissue basophils, as well as macrophages. Studying smears-imprints and tissue fluid using the "skin window" method at various stages of the eczematous reaction, the same author showed that in the acute period, along with the migration of a large number of lymphocytes, tissue eosinophilia is observed. In the subacute phase, it is mainly macrophages that migrate, which indicates the role of hypersensitivity of both types in the pathogenesis of eczematous reactions. The clinical, physiological, biochemical and pathomorphological studies she conducted give reason to believe that all clinical forms of eczema are essentially a single pathological process with a common pathogenetic mechanism.

It should be noted that the most pronounced immunomorphological changes are observed in contact and especially in microbial eczema. In the latter, electron microscopy of the dermal infiltrate reveals clusters of small lymphocytes, including activated forms with well-developed organelles and large cerebriform nuclei, macrophages, cells with high synthetic activity of protein, differentiating into plasma cells, degranulated forms of tissue basophils. Contacts of epidermal macrophages with lymphocytes are noted. In contact eczema, an increase in the number of epidermal macrophages is observed, often in contact with lymphocytes, edema of the epidermis with the presence of lymphocytes and macrophages in the expanded intercellular spaces. A large number of macrophages with multiple lysosomal structures are found in the dermal infiltrate. Lymphocytes sometimes have a cerebriform nucleus and well-developed organelles.

Changes in the vessels are similar to those in experimental contact dermatitis and are characterized by signs of hypertrophy and hyperplasia of the endothelium and perithelium, thickening and duplication of the basement membrane.

The above data on the histogenesis of the eczematous reaction indicate processes characteristic of delayed-type hypersensitivity.

In the development of the eczematous reaction, in various cases a certain clinical and morphological picture is revealed depending on the action of a complex of unfavorable factors, including infection. In this regard, a distinction is made between dyshidrotic, microbial and seborrheic eczema.

Dyshidrotic eczema is characterized by a rash, mainly on the palms and canvases, of small blisters that can merge to form small blisters, and after opening - erosive surfaces. Weeping is less pronounced than with true eczema. With a long course, eczema-like lesions can appear on other areas of the skin. Secondary infection is often observed.

Pathomorphology. Intraepidermal blisters are found, sometimes so closely adjacent to each other that only thin layers of dead epidermal cells are visible between them. The blisters may be spongiotic, as in true eczema. Some authors associate the formation of blisters with stretching and rupture of the sweat gland duct.

Microbial eczema. Sensitization to pyogenic bacteria is of great importance in the development of the disease; it often develops as a complication of chronic inflammatory processes (varicose ulcers, osteomyelitis, etc.). Clinically, it appears as the presence of isolated, asymmetrically located lesions on the skin of the distal parts of the extremities (especially on the shins), quite sharply outlined, infiltrated, often weeping, covered with scaly crusts, along the periphery of which vesicular-pustular rashes are detected. With a long-term recurrent course, eczematous rashes may appear in places remote from the main lesion.

Pathomorphology of eczematous skin reaction (eczema). The picture resembles that of seborrheic eczema, but is usually distinguished by massive spongiosis and the presence of blisters filled with serous fluid with an admixture of neutrophilic granulocytes, often acanthosis.

Seborrheic eczema. Constitutional factors, metabolic disorders, and dysfunction of the sebaceous glands are important in the development of the disease. The lesions are located on the so-called seborrheic areas in the form of rather sharply defined yellowish-red plaques, oval, round or irregular in shape, abundantly covered with scaly crusts, which gives them a psoriasiform appearance. Diffuse bran-like peeling on the scalp and acne are often found. Weeping is usually insignificant, with the exception of lesions located in folds.

Pathomorphology of eczematous skin reaction (eczema). Usually hyperkeratosis, parakeratosis, intra- and intercellular edema and slight acanthosis are observed. Sometimes exocytosis, edema and varying degrees of dermal infiltration, mainly of a lymphocytic nature, can be observed. In the area of varicose ulcers, fibrosis of the dermis is added to these changes, in which lymphohistiocytic infiltrates are visible, often with the presence of plasma cells. Sometimes acanthosis with elongation of epidermal outgrowths can be observed, which resembles a picture of neurodermatitis or psoriasis. Perifolliculitis is often observed. Sometimes lipids are found in the superficial cells of the germinal and horny layers, as well as in the endothelium of the vessels of the superficial dermal network, which does not happen in true eczema. In addition, a distinctive feature of seborrheic eczema is the presence of coccal flora in the superficial parts of the horny layer. In the dermis there is a perifollicular infiltrate containing lymphocytes, neutrophilic granulocytes, and sometimes plasma cells. A slight thickening of the vessel walls is possible. Elastic and collagen fibers are usually not affected.

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