Mineral metabolism disorders (mineral dystrophies): causes, symptoms, diagnosis, treatment

In the skin, the most important is the disruption of calcium metabolism (calcinosis of the skin). Calcium plays a major role in the permeability of cell membranes, excitability of nerve formations, blood clotting, regulation of acid-base metabolism, and formation of the skeleton.

Calcium metabolism is regulated by neurohormonal pathways, with the parathyroid glands (parathyroid hormone) and the thyroid gland (calcitonin), protein colloids, the pH of the environment and the level of calcium in the blood, as well as the condition of the tissues, being of greatest importance.

Calcinosis. Calcium metabolism disorder is accompanied by 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 regard, four forms of cutaneous calcinosis are distinguished: metastatic, dystrophic, metabolic and idiopathic. According to prevalence, the process is divided into limited and universal.

Metastatic calcinosis cutis is rare and develops as a result of hypercalcemia or hyperphosphatemia, which is usually associated with hyperthyroidism, bone diseases accompanied by their destruction (osteomyelitis, fibrous osteolystrophy, myeloma, hypervitaminosis B12, in chronic renal failure in patients who have received long-term hemodialysis. Clinical symptoms of metastatic calcinosis cutis are expressed in the appearance of symmetrical, most often located in the area of the joints, small and large nodular formations of "stony" density, painful when pressed. The skin is yellowish or bluish-red, fused with them. Over time, the nodes can soften with the formation of difficult-to-heal ulcers and fistulas, from which milky-white crumbling masses ("calcium gummas") are released.

Pathomorphology. Lime salts are stained dark purple by hematoxylin and eosin, and black by the Kossa method. In this type of calcification, massive salt deposits are found in the subcutaneous tissue, and individual granules and small clusters are detected in the dermis. Necrosis with a giant cell reaction around and subsequent fibrosis is often observed in places where lime salts are deposited.

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

Pathomorphology. Small accumulations of lime salts are found in the dermis and massive ones in the subcutaneous tissue, around which a giant cell reaction occurs, and in the later stages - encapsulation. Some authors point out the 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 some enzymes.

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

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

Idiopathic calcinosis cutis is divided into two types: tumor-like (nodular) and limited calcinosis of the scrotum.

Tumor-like calcinosis is characterized by the appearance of single tumor-like formations, most often located on the head of children. This is usually a familial disease accompanied by phosphatemia.

The pathomorphology is similar to that described above for other types of cutaneous calcinosis. Electron microscopic examination of the lesions showed that the deposits in this type of calcinosis consist of apatite crystals deposited within collagen fibers.

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

Electron microscopic examination shows that lime salts are deposited inside the sweat gland duct.

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