Disorders of mineral metabolism (mineral dystrophy): causes, symptoms, diagnosis, treatment

In the skin, the most important is the violation of calcium metabolism (calcification of the skin). Calcium plays an important role in the permeability of cell membranes, the excitability of nerve formations, blood coagulation, regulation of acid-base metabolism, and the formation of the skeleton.

The exchange of calcium is regulated by the neurohormonal route, the most important are the parathyroid glands (parathyroid hormone) and the thyroid gland (calcitonin), protein colloids, the pH of the medium and the level of calcium in the blood, and the tissue state.

Calcification. Violation of calcium metabolism is accompanied by the deposition of lime salts in tissues, as well as in the skin (calcareous dystrophy, or calcification). The mechanism of calcification is different, and in this connection there are four forms of cutaneous calcification: metastatic, dystrophic, metabolic and idiopathic. The prevalence of the process is divided into a limited and universal.

Metastatic calcification of the skin is rare, it develops as a result of hypercalcemia or hyperphosphataemia, which is usually associated with hyperthyroidism, bone disease accompanied by their destruction (osteomyelitis, fibrosis osteolystrophy, myeloma, hypervitaminosis B12, chronic renal failure in patients who have been receiving hemodialysis for a long time. Metastatic calcification of the skin is expressed in the appearance of symmetrical, located most often in the area of the joints of small- and coarse- The skin is yellowish or cyanotic-red, it is soldered to them.In the course of time, the nodes may soften with the formation of difficult healing ulcers and fistulas, from which milky white crumbs ("calcium gum") are prominent, .

Pathomorphology. Lime salts are stained with hematoxylin and eosin in a dark purple color, according to the Cossa method, in black. In this form of calcification, massive deposits of salts are found in the subcutaneous tissue, and in the dermis separate granules and small clusters are identified. In places where lime salts are deposited, necrosis with a giant cell reaction around and subsequent fibrosis is often observed.

Dystrophic calcification of the skin is not accompanied by general disturbances of phosphorus-calcium metabolism. It can be observed in a variety of skin diseases: dermatomyositis, systemic scleroderma (Tibierja-Weissenbach syndrome), tumors, cysts, tuberculosis, varicose ulcers, Chernogubov-Ehlers-Danlos syndrome, elastic pseudocanthoma, perichondritis of the auricle, etc.

Pathomorphology. Detect small accumulations of lime salts in the dermis and massive in the subcutaneous tissue, around which a giant cell reaction develops, and in the later stages - encapsulation. Some authors indicate a lack of parallelism between the severity of tissue damage and the degree of calcification. It is noted that calcification is preceded by an increase in the metabolic activity of cells, proteins, glycosaminoglycans, and certain enzymes.

Metabolic calcification is also not accompanied by a change in the calcium content of the blood. Pathogenetic factors include increased calcium absorption by tissues, trophic and hormonal disorders. The main importance is usually attached to the instability of the buffer systems, and therefore calcium is not retained in the blood and tissue fluid. In the development of metabolic calcification, hereditary predisposition is important.

Metabolic calcification can be universal, widespread and local. Clinical manifestations on the skin are similar to those described above. In the universal process, a characteristic calcium deposit, in addition to calcification, is the progressive deposition of calcium in muscles and tendons in children and adolescents. Local or common forms of this type of calcification are observed in systemic lupus erythematosus, scleroderma, dermatomyositis and other diseases. The histological pattern is similar to that described above.

Idiopathic calcification of the skin is divided into two types: tumorous (nodular) and limited calcification of the scrotum.

Tumor calcification is characterized by the appearance of single tumor-like formations, often located on the head in children. This is usually a family illness accompanied by phosphatemia.

Pathomorphology is similar to that described above with other types of calcification of the skin. Electron-microscopic examination of the lesion sites showed that deposits in this form of calcification consist of apatite crystals deposited within the collagen fibers.

There are superficial deposits of calcium salts in the skin of the limbs and face in the form of verruzel nodules (subepidermal calcification). Calcium salts in this form of calcification are detected in the upper part of the dermis, sometimes in deeper parts of the dermis. They have globules and granules, around which a giant cell reaction often develops. The epidermis is often in a state of acanthosis, sometimes calcium granules are found in it.

Electron microscopy shows that the lime salts are deposited within the duct of the sweat gland.

[1], [2], [3], [4], [5], [6]