Lax skin: causes, symptoms, diagnosis, treatment

Flabby skin (syn.: dermatochalasis, generalized elastolysis) is a heterogeneous group of generalized connective tissue diseases with common clinical and histological changes in the skin. Hereditary and acquired forms are distinguished. Among the hereditary lesions, autosomal dominant and autosomal recessive types are distinguished. A sex-linked type of the disease has been described, in which the symptoms of flabby skin were combined with hyperelasticity. The autosomal dominant type of the disease has a benign course, the connective tissue lesion affects mainly the skin, while the recessive type is characterized by generalized connective tissue lesion.

The causes and pathogenesis of flaccid skin have not been sufficiently studied. The possibility of a disruption in collagen synthesis with intracellular accumulation of procollagen, a decrease in tropoplastin production, an increase in elastase activity with a decrease in the function of its inhibitors, lysine oxidase deficiency (in the X-linked form), a decrease in copper concentration, and the role of autoimmune reactions are indicated. Infectious processes and immune disorders are important in the development of the acquired form of the disease.

The clinical picture of skin lesions is the same for all types of the disease. The skin is mobile, easily stretched, after the stretching stops it very slowly returns to its original position, under the weight of its own mass it hangs down, forming folds and wrinkles, especially pronounced on the face in the eyelid area (blepharochalasis), nasolabial fold, on the neck, chest, abdomen, back, which is why young patients look prematurely aged. A hooked nose with everted nostrils and a long upper lip, drooping ears, a low hoarse voice, which is due to stretching of the vocal cords, are characteristic.

In the case of autosomal recessive inheritance, two clinical forms of lax skin are distinguished. The first is characterized by a generalized disorder of the structure of elastic fibers, manifested as pulmonary emphysema, with progressive pulmonary insufficiency, anomalies in the structure of the cardiovascular system with damage to the elastic membrane of arterial vessels, including the pulmonary artery and aorta, diverticula in the gastrointestinal tract and genitourinary organs. Such defects can be the cause of death at an early age. The second form is manifested by developmental defects: pre- and postnatal growth retardation, congenital hip dislocation, various bone defects and non-closure of the anterior fontanelle.

The X-linked variant of lax skin is characterized by the presence of bony protrusions on either side of the foramen magnum and bladder diverticula. Patients usually have a hooked nose and an elongated upper lip. Fibroblasts from patients and heterozygous carriers in culture contain a lot of copper, suggesting a defect in its metabolism and an associated decrease in lysine oxidase activity.

Pamomorphology of flaccid skin. The epidermis is slightly changed, sometimes slightly atrophic. Collagen fibers of the upper part of the dermis are loosened, in the reticular layer their random arrangement is revealed. The amount of elastic fibers throughout the dermis is noticeably reduced, especially in its upper parts. Oxytalan fibers are absent, elaunin fibers are barely noticeable in the subpapillary plexus. Elastic fibers of the reticular layer of the dermis are of varying thickness, fragmented or have a granular appearance with unclear contours, sometimes in the form of dust-like granules located between bundles of collagen fibers; in the lower part of the dermis, elastic fibers are thin, long, wavy, they are absent around the sebaceous-hair follicles. Histochemical examination revealed an increase in the content of glycosaminoglycans in the ground substance of the dermis, which is possibly associated with changes in elastic fibers. A similar pathology of elastic fibers was found in the aortic wall, in the lung tissue of patients with cardiorespiratory manifestations of the disease. Electron microscopy in the papillary layer of the dermis revealed only microfibrils resembling oxytalan fibers, elaunin fibers are absent. In the reticular layer, short, irregularly shaped or spherical elastic fibers are found, located among slightly changed collagen fibers. Their matrix is electron-transparent, without microfibrils, which are usually visible among the amorphous matrix. In places where microfibrils are normally visible along the periphery of the elastic fiber, a granular-fibrillar substance is revealed. Separate bundles of microfibrils are located near the elastic fibers. In these places, SR Sayers et al. (1980) found electron-dense deposits of amorphous substance of the same localization. In the deeper parts of the dermis, elastic fibers are less altered, although they appear thin and short, and fibroblasts show signs of enhanced protein-synthetic function.

Histogenesis of lax skin. Normally, microfibrils form a network that plays an important role in the orientation of elastin molecules (the so-called vector synthesis) in lateral and end-to-end junctions, which ensures the normal structure of the elastic fiber and its physiological usefulness. In lax skin, the ratio between the two main components of the elastic fiber is disrupted - the protein elastin, which makes up the amorphous matrix of the fiber, and the microfibrils. M. Ledoux-Corbusier (1983) believes that in the autosomal recessive type of lax skin, there is no destruction of elastic fibers, but their underdevelopment. The absence of elaunin fibers and a small amount of oxytalan fibers indicate a violation of elastogenesis in its early stages. Elastogenesis is completely absent in the papillary layer and is blocked in the reticular layer. In this regard, the term "elastolysis" is inappropriate to use and it is more correct to consider the main process as a generalized disorder of elastogenesis. Some authors, in addition to elastic ones, find changes in collagen fibers in the form of unevenness of their diameter and splitting, similar to that in Chernogubov-Ehlers-Danlos syndrome. Apparently, this is associated with the commonality of enzymatic regulation of individual stages of the biosynthesis of collagen and elastic fibers.

Acquired, or secondary, elastolysis, unlike hereditary types, usually occurs in adults as a result of various inflammatory skin diseases (post-inflammatory dermatochalasis): urticaria, burns, contact dermatitis, eczema, but can also occur without previous inflammation.

Elastolysis can also be a manifestation of Chernogubov-Ehlers-Danlos syndrome with autosomal recessive inheritance, elastic pseudoxanthoma, autosomal dominant amyloidosis. It is believed that the development of acquired elastolysis is based on hereditary predisposition, and previous skin diseases are only a resolving factor.

Unlike hereditary forms, in addition to the usual manifestations of flabby skin, residual manifestations of the dermatosis against which it developed are often visible on the skin. At the same time, lesions of internal organs - lungs, heart, gastrointestinal tract, similar to those described in the autosomal recessive type of flabby skin - are not uncommon, which makes the above division of this disease into hereditary and acquired forms very conditional and requires the development of additional criteria.

Pathomorphology of lax skin. The histological picture of acquired elastolysis, in addition to the changes listed, may include an inflammatory reaction indicating changes preceding the development of lax skin. Lymphohistiocytic infiltrates, giant cells of foreign bodies, admixture of eosinophilic granulocytes, eosinophilic spongiosis, calcium deposits are sometimes noted in the dermis. H. Nanko et al. (1979) believe that skin changes in acquired elastolysis occur as an autoimmune reaction, which is confirmed by the description of several cases of a combination of acquired elastolysis with autoimmune diseases - multiple myeloma, systemic lupus erythematosus and cutaneous amyloidosis. Electron microscopic examination of the skin in acquired elastolysis revealed altered elastic fibers along with normal ones. They are fragmented, surrounded by small short filaments, and the remains of elastic fibers are visible in the form of electron-dense amorphous material. Thus, in the acquired form, the destruction of normally formed elastic fibers is observed.

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