Carbohydrate dystrophies: causes, symptoms, diagnosis, treatment

Carbohydrate dystrophies can be parenchymatous and mesenchymal. Carbohydrates found in cells and tissues are identified using histochemical research methods. They are divided into polysaccharides and glucoproteins.

Mucopolysaccharides can be neutral, tightly bound to proteins (chitin) and acidic (glycosaminoglycans), which include hyaluronic acid, chondroitin sulfuric acid and heparin. Glucoprotsides differ from mucopolysaccharides in that the hexosamine content in them does not exceed 4%. These include mucin and mucoids. Mucin is found in mucus produced by mucous membranes, mucoids are part of many tissues (heart valves, arterial walls, skin, cartilage). Polysaccharides are detected in tissues by the PAS reaction, in which a crimson color appears at the sites of localization of polysaccharides. To identify glycogen, control sections are treated with diastase or amylase, after which the red color associated with the presence of glycogen disappears. Glycosaminoglycans and glucoproteins are determined in tissues by staining with toluidine blue as a reddish-lilac coloration in the areas where glycosaminoglycans are located.

Carbohydrate dystrophy caused by a disorder of glycogen metabolism is observed in the skin with hereditary carbohydrate dystrophy - glycogenoses, and with a disorder of glucoprotein metabolism it manifests itself as mucous dystrophy.

Mucous dystrophy - carbohydrate dystrophy caused by a disorder of glucoprotein metabolism in cells, leads to the accumulation of mucins and mucoids in them. In this case, not only mucus formation increases, but also changes in the physicochemical properties of mucus. Many cells die and desquamate, which leads to the formation of cysts. Examples of this type of dystrophy in the skin can be follicular mucinosis and mucous mesenchymal dystrophy of the skin.

Mucous dystrophy can develop in both the epidermis and the dermis. Dermal mucin normally forms the main substance of the connective tissue of the dermis and consists of glycosaminoglycans, especially hyaluronic acid. This type of mucin is PAS-negative, stains with Alcian blue at pH from 2.5 to 0.4 metachromatically, hyaluronidase-labile. Epithelial mucin, called sialomucin, contains neutral mucopolysaccharides, often glycosaminoglycans. It is found in the granules of dark mucoid-secreting cells of the eccrine glands, a little in the granules of the apocrine glands, in the cells of cysts of the oral mucosa, in tumor cells in Paget's disease with perianal localization of lesions and adenocarcinoma of the digestive tract. Epithelial mucin is PAS-positive, hyaluronidase- and diastase-resistant, can be stained with alcian blue at pH from 2.5 to 0.4, will give a weak metachromasia of toluidine blue.

Cutaneous mucinosis is a mesenchymal carbohydrate dystrophy characterized by the release of chromotropic substances (glycosaminoglycans) from protein bonds and accumulating in the intercellular substance. In this case, collagen fibers of the connective tissue are replaced by a mucus-like mass (mucinosis), and its cells become branched and acquire a star-shaped appearance.

Cutaneous mucinosis can be localized or diffuse, often associated with dysfunction of the thyroid gland (hypo- and hyperthyroidism), although these changes can also be observed with normal function. In this case, mucin is found in the tissues, stained bluish with hematoxylin and eosin, possessing pronounced metachromatic properties when stained with toluidine blue and cresyl violet. On a general blue background, mucin looks reddish-violet. Mucicarmine stains it red.

In hypothyroidism, the cause of which is primary atrophy and inflammatory changes in the thyroid gland, the skin is pale, dry, waxy. Along with this, generalized or tuberous myxedema of the skin develops. In the generalized form, continuous edema of the skin develops, most often on the face, neck, hands, shins and feet. The skin is slightly mobile, poorly gathers into folds, the hair is dull and brittle, eyebrows may be absent, and the legs also become brittle.

In tuberous myxedema, skin lesions, although widespread, are less diffuse, appearing as nodular compactions, limited foci resembling plaques with a shagreen surface, resulting from the close arrangement of elements. General symptoms of hypothyroidism are less pronounced than in diffuse myxedema.

Pathomorphology. The epidermis is mostly unchanged, with the exception of the skin of the elbows and knee joints, where acanthosis may be observed. The dermis is significantly thickened, with swelling of collagen fibers and their spreading by bluish masses of mucin, which are located in the form of a delicate mesh mainly around the vessels and in the connective tissue capsules of the hair follicles. The content of glycosaminoglycans increases compared to the norm by 6-16 times. Electron microscopy reveals changes in fibroblastic elements, in which collagen fibers are found.

In hyperthyroidism, or thyrotoxicosis, in addition to the characteristic triad - goiter, tachycardia, exophthalmos - myasthenia is observed, associated with the accumulation of glycosaminoglycans in the muscle stroma, sometimes osteoarthropathy with subperiosteal ossifying periostitis of the distal ends of the phalanges, which look like drumsticks. On the skin of the face and trunk there may be erythema, dermographism with an urticarial reaction. Hyperhidrosis, hyperpigmentation, trophic disorders (hair loss, nail dystrophy) are often encountered. diseases of the sebaceous glands. Typical pretibial myxedema may be observed, clinically characterized by the development of flat cushion-shaped seals of various sizes, the color of normal skin or yellowish-gray with a distinct pattern of hair follicles. Sometimes, with a long course, elephantiasis may develop. In the development of this form of mucinosis, in addition to thyroid dysfunction, other factors probably play a role, in particular diencephalic disorders, hypersecretion of thyroid-stimulating hormone, and autoimmune reactions.

Pathomorphology. Massive hyperkeratosis with smoothing of epidermal outgrowths. In the dermis - large accumulations of mucin, especially in the middle sections, as a result of which it is thickened, collagen fibers are loosened. The number of fibroblasts is increased, some of them are transformed into mucous cells of stellate outlines, surrounded by munin. GW Korting (1967) called these cells mucoblasts. In them, electron microscopy reveals a large number of organelles. In addition to these cells, a large number of tissue basophils are found. The capillaries of the upper third of the dermis are dilated, their walls are thickened, in places there are small lymphocytic infiltrates.

Cutaneous mucinosis may be observed with normal thyroid function. The following forms are encountered: Arndt-Gottron scleromyxedema, lichen myxedema (papular myxedema), Buschke's adult scleredemia, follicular mucinosis, and reticulate erythematous mucinous syndrome (REM syndrome).

Myxedema lichen (papular myxedema) is manifested by a rash of small shiny hemispherical nodules, densely located mainly on the skin of the trunk, face and upper limbs. In Arndt-Gottron scleromyxedema, the rash is similar, but there is a more pronounced tendency to merge with the formation of extensive foci, often sharply edematous, especially on the face and hands. In the area of large joints, seals are formed with the formation of rough skin folds, on the face there may be nodularity and diffuse infiltration. With a long course of the disease, as a result of skin sclerosis, facial expressions are impaired, movements of the upper limbs are difficult. There is a point of view that Arndt-Gottron scleromyxedema is a variant of myxedema lichen.

Pathomorphology. In myxedematous lichen, large mucin fields are found in the skin, especially in the upper parts of the dermis, which look like basophilic masses when stained with hematoxylin and eosin. Collagen fibers in these areas are loosened, thinned, palely stained, cellular elements are scanty, stellate cells predominate. Vessels are dilated, their walls are edematous, do not contain mucin, sometimes there may be a small number of lymphocytes and fibroblasts around them.

In Arndt-Gottron scleromyxedema there is diffuse thickening of the dermis without intensive proliferation of fibroblasts. Mucin is usually detected in its upper third. Electron microscopy revealed an increase in the number of connective tissue elements and tissue basophils. There is close contact of numerous cells with collagen fibrils. L. Johnson et al. (1973) identified two types of fibroblasts: elongated and stellate. The former synthesize glycosaminoglycans, the latter - collagen fibers.

Scleredema of adults Buschke belongs to a group of connective tissue diseases of unclear genesis. Many point to the development of scleredema after acute infectious diseases, especially those caused by streptococcus. Sometimes scleredema is combined with diabetes mellitus, especially resistant to therapy, and can be observed in children. It manifests itself as swelling of the neck and face, which symmetrically spreads down to the shoulders, trunk and arms. The hands and lower body are usually not affected. In most cases, the disease regresses within a few months, but in some patients the process takes on a protracted, multi-year course; in rare cases, systemic changes in the heart muscle and other organs are possible.

Pathomorphology. The dermis is 3 times thicker than normal. Edema is observed throughout its thickness, especially in the deep sections, as a result of which the collagen bundles become split, and the elastic fibers are fragmented. The edema can be so strong that it leads to the formation of cracks of various sizes (fenestration). The terminal parts of the sweat glands are localized in the lower or middle sections of the dermis, and not at the border with the subcutaneous tissue, as is normal. The subcutaneous tissue is sometimes mixed with dense connective tissue. In some areas of the dermis, an increase in the number of fibroblasts is detected, among which there are many tissue basophils. In the early stages of the disease, histochemical reactions often reveal hyaluronic acid between the bundles of collagen fibers, especially in the fenestration areas, which can be detected by staining with colloidal iron, toluidine blue or alcian blue. In cases of prolonged disease, hyaluronic acid in collagen bundles may not be detected. Focal infiltrates are found around the vessels. Electron microscopy reveals an increase in the number of connective tissue cells with a large number of organelles, as well as an increase in the main substance of the dermis, especially near the elastic fibers. Collagen fibers in places form dense bundles or are loosened, which resembles the early stages of scleroderma. The disease is differentiated from scleroderma, in which collagen fibers in the subcutaneous tissue are usually homogenized and hyalinized, weakly stained with eosin using the Masson method. In Buschke's adult scleredema, collagen bundles are without any special changes and are stained with hematoxylin and eosin as usual. In some cases, it is very difficult to draw a line between these two diseases.

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