Mesenchymal skin dysproteinosis: causes, symptoms, diagnosis, treatment

When mesenchymal dysproteinosis in the connective tissue of the dermis and the walls of the blood vessels, protein metabolism is disrupted. At the same time, metabolic products accumulate, which can come with blood or lymph, or are formed as a result of improper synthesis or disorganization of the main substance of the dermis and its fibrous substances. Mesenchymal dystrophies of the skin include, as in other organs, mucoid swelling, fibrinoid changes, hyalinosis and amyloidosis.

The main protein of connective tissue is collagen, which along with glycosaminoglycans is part of collagen, elastic and reticulin fibers, as well as basal membranes. Sometimes mucoid swelling, fibrinoid alteration and hyalinosis are the result of disorganization of the connective tissue resulting from increased tissue-vascular permeability (plasmorrhagia), the destruction of connective tissue elements and the formation of protein complexes.

Mucoid swelling is a concept first introduced by A.I. Strukovym (1961), represents metabolic disturbances of connective tissue of reversible character, consisting in the accumulation and redistribution in the main substance of glycosaminoglycans. Due to the hydrophilicity of glycosaminoglycans, tissue and vascular permeability increases, resulting in plasma proteins (globulins) and glycoproteins, which leads to swelling of the intercellular substance. At the same time, the basic substance becomes basophilic, and when it is painted with toluidine blue it acquires a pinkish-lilac color (metachromasia). Collagen fibers swell, are subjected to defibration, which can be accompanied by a cellular reaction in the form of lymphocytic, plasmacytic and histiocytic infiltrates. Mucoid swelling occurs mainly in the walls of the arteries, in the dermis with collagen diseases (lupus erythematosus, scleroderma), allergic dermatitis, hypoxia, thyroid dysfunction.

Fibrinoid swelling of the connective tissue is a metabolic disturbance of an irreversible nature, in which a fibrinoid is formed that does not occur normally. Fibrinoid-altered areas are sharply eosinophilic, according to van Gyzon's method they are colored yellow, often homogeneous. At the beginning of the process glycosaminoglycans are detected in these areas, metachromatically colored toluidine blue in lilac color, later giving a sharply positive Schick reaction. In the terminal stages (fibrinoid necrosis) the connective tissue is degraded to form amorphous detritus. It is pyroninophilic in coloring according to the method of Brother, Schick-positive and diatase-resistant. Fibrinoid changes in the connective tissue of the dermis develop in allergic vasculitis, sometimes with the formation of fibrinoids in the vascular walls themselves, in rheumatic nodules, in lupus erythematosus, especially in the subepidermal parts of the skin and under the phenomenon of Arthus.

Regarding the composition and origin of fibrinoids, there is no single pattern. There are different in composition and structure of fibrinoids in diseases caused by various pathogenetic factors. Among these factors, the joint venture. Lebedev (1982) considers the destruction of collagen fibers, changes in the polysaccharide composition of the basic substance of the connective tissue and the increase in vascular permeability, which ensures the exudation of high-molecular proteins and glycoproteins of the blood plasma. In diseases caused by immune disorders, the formation of fibrin is associated with immunocomplex damage to the microcirculatory bed and connective tissue, which is especially pronounced in systemic lupus erythematosus, when the action of immune complexes causes destruction of tissue and fibrin exudation. In immune complexes, complement and fibrin predominate, and this fibrinoid is called "fibrinoid immune complexes", "fibrinoid destruction". The fibrinoid, formed as a result of angioedema disorders (plasmorrhagia), is called the fibrinoid of insudation.

Hyalinosis is a dystrophic process that mainly affects connective tissue and is expressed in the deposition of homogeneous eosinophilic masses of different composition. Occasionally, as synonyms, the names "colloid", "hyaline or colloid bodies" are used.

Hyaline - fibrillar protein, which includes plasma proteins (fibrin). In it immunohistochemical methods detect immune globulins, components of complement, and also lipids. Hyaline is stained in the dermis with acidic dyes (eosin, sour fuchsin), Schick-positive, diastasis-resistant. There are three types of hyaline: simple, formed as a result of the release of unchanged blood plasma with angioedema; lipogialin, containing lipoids and beta-lipoproteins (in diabetes mellitus); and a complex hyaline consisting of immune complexes, fibrin and necrotically altered parts of the vascular wall (for example, in collagen diseases). Hyaline is found in the dermis with hyalinosis of the skin and mucous membranes, with porphyria and a cylinder. In addition to systemic hyalinosis, local hyalinosis occurs as a result of sclerosis in the scars, in the scarring necrotic tissue. In the places of fibrinoid changes.

An example of systemic skin hyalinosis is the hyalinosis of the skin and mucous membranes (Urbach-Vite syndrome), which is an autosomal recessive disease that occurs in the first years of life and is characterized by the deposition of extracellular amorphous masses in the connective tissue of the skin, mucous membranes and internal organon. It is believed that collagen metabolism is primarily disturbed. Dermal manifestations consist in the development of densely located yellowish-whitish nodules predominantly on the skin of the face (especially the eyelids and lips), fingers, elbows, armpits, and knee joints. Due to the nodules, there are infiltrated foci with a waxy, coarse, sometimes hypertrophic, verruccus surface reminiscent of acanthosis nigricans. Perhaps, especially in early childhood, the appearance of itchy bubbles, blisters, varioliform elements, erosions, ulcers, leading to ossicular-like scarring, dyschromia. Similar and, as a rule, earlier arising changes are observed in the mouth cavity on the mucous membrane of the cheeks resembling leukoplakia, or in the form of ulcers with scarring on tonsils, with periodic inflammatory reactions, including granulations in the pharynx and larynx. The defeat of the latter causes the earliest symptom - the hoarseness of the voice in infancy. There is macroglossia. Other mucous membranes are also affected, hypo- and aplasia of the teeth, especially the upper incisors, slow growth of nails and hair are common.

Pathomorphology. In the so-called infiltrative foci, a typical picture of hyalinosis with deposition of homogeneous weak-eosinophilic Schick-positive, diastasis-resistant substances in the dermis is found. These substances are positively stained with Sudan III, shards, Sudan in black, they reveal phospholipids. In the early stages of the process, homogeneous masses are deposited in the walls of the capillaries and in the region of the eccrine sweat glands, which then atrophy; in subsequent stages - ribbon-like homogeneous masses, in which there may be slits in places - places of lipid deposition. Similar changes are observed in clinically unchanged skin, but they are much weaker. Electron microscopic examination showed that, among normal collagen fibers, filaments appearing in an amorphous fine-granular material appear in various amounts, closely related to the active fibroblasts producing these masses. With hyalinosis, as a result of transudation, the basal membranes of the capillaries change. They significantly thicken, become multilayered, which is associated with an increase in the amount of collagen IV and V types.

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