Sometimes in clinical practice there is such a phenomenon as parenchymal dystrophy. Pathological anatomy refers them to metabolic disorders in cells. In simple terms, the process of nutrition and accumulation of nutrients is disrupted in the body, which leads to morphological (visual) changes. You can identify such a pathology in the section or after a series of highly specific tests. Parenchymal and stromal-vascular dystrophies underlie many fatal diseases.
Definition
Parenchymal dystrophies are pathological processes that lead to changes in the structure of organ cells. Among the mechanisms of the development of the disease, there are disorders of cell self-regulation with energy deficiency, fermentopathy, dyscirculatory disorders (blood, lymph, interstitium, intercellular fluid), endocrine and cerebral dystrophies.
There are several mechanisms of dystrophy:
- infiltration, that is, excessive transport of metabolic products from the blood into the cell or intercellular space, due to a malfunction in the enzyme systems of the body;
- decomposition, or phanerosis, representsis a breakdown of intracellular structures, which leads to metabolic disorders and the accumulation of under-oxidized metabolic products;
- perverted synthesis of substances that normally the cell does not reproduce;
- transformation of nutrients entering the cell to build one type of end products (proteins, fats or carbohydrates).
Classification
Pathologists distinguish the following types of parenchymal dystrophies:
1. Depending on morphological changes:
- purely parenchymal;
- stromal-vascular;
- mixed.
2. By type of accumulated substances:
- protein or dysproteinoses;
- fat or lipidoses;
- carbohydrate;
- mineral.
3. By process prevalence:
- system;
- local.
4. By time of appearance:
- purchased;
- congenital.
Pathological anatomy determines certain parenchymal dystrophies not only by the damaging agent, but also by the specifics of the affected cells. The transition of one dystrophy to another is theoretically possible, but only a combined pathology is practically possible. Parenchymal dystrophies are the essence of the process occurring in the cell, but only part of the clinical syndrome, which covers the morphological and functional insufficiency of a particular organ.
Dysproteinoses
The human body is mostly made up of proteins and water. Protein molecules arecomponent of cell walls, membranes of mitochondria and other organelles, in addition, they are in a free state in the cytoplasm. As a rule, these are enzymes.
Dysproteinosis is otherwise called a pathology such as parenchymal protein dystrophy. And its essence lies in the fact that cellular proteins change their properties, as well as undergo structural changes, such as denaturation or colliquation. Protein parenchymal dystrophies include hyaline-drop, hydropic, horny and granular dystrophies. The first three will be written in more detail, but the last, granular, is characterized by the fact that protein grains accumulate in the cells, due to which the cells stretch, and the organ increases, becomes loose, dull. That is why granular dystrophy is also called dull swelling. But scientists have doubts that this is parenchymal dystrophy. The pathanatomy of this process is such that compensatory enlarged cellular structures can be mistaken for grains, as a response to functional stress.
Hyaline drip degeneration
With this type of dystrophies, large hyaline drops appear in the cells, which eventually merge with each other and fill the entire internal space of the cell, displacing organelles or destroying them. This leads to loss of function and even cell death. Most often, the disease occurs in the kidney tissue, less often in the liver and heart.
During a cytological examination after a kidney biopsy, in addition to the accumulation of hyaline in nephrocytes, destruction of allcellular elements. This phenomenon appears if the patient develops vacuolar-lysosomal insufficiency, which leads to a decrease in the reabsorption of proteins from the primary urine. Most often, this pathology occurs with nephrotic syndrome. The most common diagnoses of such patients are glomerulonephritis and amyloidosis of the kidneys. The appearance of the organ with hyaline drop dystrophy does not change.
The situation is somewhat different in cookie cells. During microscopy, Mallory bodies are found in them, consisting of fibrils and alcoholic hyaline. Their appearance is associated with Wilson-Konovalov disease, alcoholic hepatitis, as well as biliary and Indian cirrhosis. The outcome of this process is unfavorable - necrosis of liver cells, loss of its function.
Hydropic dystrophy
This type of dystrophy differs from the others in that new organelles filled with fluid appear in the affected cells. Most often, this phenomenon can be seen in the skin and tubules of the kidneys, in the cells of the liver, muscles and adrenal glands.
Microscopically the cells are enlarged, their cytoplasm is filled with vacuoles with transparent liquid contents. The nucleus is displaced or lysed, the remaining structures are eliminated. Ultimately, the cell is a "balloon" filled with water. Therefore, hydropic dystrophy is sometimes called ballooning.
Macroscopically, organs practically do not change. The mechanism of development of this disease is a violation of colloid osmotic pressure in the cell and in the intercellular space. Because of this, the permeability of cells increases, their membranes disintegrate and the cells die. The causes of such chemical changes can be glomerulonephritis, diabetes mellitus, kidney amyloidosis. Viral and toxic hepatitis contribute to cell changes in the liver. On the skin, hydropic dystrophy can be caused by the variola virus.
This pathological process ends with focal or total necrosis, so the morphology and function of the organs deteriorate rapidly.
Hornous dystrophy
Pathological keratinization of organs is an excessive accumulation of horny matter in the surface layers of the skin, for example, hyperkeratosis or ichthyosis, as well as the appearance of horny matter where, as a rule, it should not be - on the mucous membranes (leukoplakia, squamous cell carcinoma). This process can be both local and total.
The causes of this type of disease can be disorders of the ectodermal bud during embryogenesis, chronic inflammatory tissue changes, viral infections and vitamin deficiency.
If treatment is started immediately after the first symptoms appear, the tissues can still recover, but in advanced cases, recovery is no longer possible. Long-standing areas of horny degeneration can degenerate into skin cancer, and congenital ichthyosis is incompatible with fetal life.
Hereditary dystrophies
Hereditary parenchymal dystrophy occurs due to congenital fermentopathy. These diseases are otherwise called storage diseases, because due to metabolic disorders, metabolic products accumulate in cells andbody fluids, poisoning it. The best known members of this group are phenylketonuria, tyrosinosis, and cystinosis.
Target organs for PKU are the central nervous system, muscles, skin and fluids (blood, urine). Metabolic products in tyrosinosis accumulate in the cells of the liver, kidneys and bones. Cystinosis also affects the liver and kidneys, but also affects the spleen, eyeballs, bone marrow, lymphatic system, and skin.
Lipidoses
Lipids are contained in every cell, they can be both separately and in combination with proteins and be structural units of the cell membrane, as well as other ultrastructures. In addition, glycerol and fatty acids are found in the cytoplasm. In order to detect them in tissues, special methods of fixation and staining are used, for example, sudan black or red, osmic acid, Nile blue sulfate. After specific preparation, the preparations are carefully examined under an electron microscope.
Parenchymal fatty degeneration manifests itself in the form of excessive accumulation of fats where they should be, and the appearance of lipids where they should not be. As a rule, neutral fats accumulate. The target organs are the same as in protein dystrophy - the heart, kidneys and liver.
Fatty parenchymal degeneration of the myocardium begins with the appearance in myocytes of very small droplets of fat, the so-called. dusty obesity. If the process does not stop at this stage, then over time the drops merge and become larger,until they occupy the entire cytoplasm. At the same time, organelles disintegrate, the striation of muscle fibers disappears. The disease is locally manifested near the venous vascular bed.
Macroscopically, parenchymal fatty degeneration manifests itself in different ways, it all depends on the stage of the process. At the very beginning, the diagnosis can only be made under a microscope, but over time, the heart enlarges due to the expansion of the chambers, its walls become thin and flabby, dirty yellow stripes are visible when the myocardium is cut. Pathophysiologists came up with a name for this organ: “tiger heart.”
Fatty degeneration of parenchymal organs develops according to three main mechanisms.
- Increased supply of free fatty acids to myocardial cells.
- Impaired fat metabolism.
- Decomposition of lipoprotein structures inside the cell.
Most often these mechanisms are triggered during hypoxia, infection (diphtheria, tuberculosis, sepsis) and intoxication of the body with chlorine, phosphorus or arsenic.
As a rule, fatty degeneration is reversible, and violations of cellular structures are restored over time. But if the process is strongly launched, then everything ends with the death of the tissue and organ. Clinicians distinguish between the following diseases associated with the accumulation of fat in cells:
- Gaucher disease;
- Tay-Sachs disease;
- Niemann-Pick disease and others.
Carbohydrate dystrophies
All carbohydrates that are in the body can be divided into polysaccharides (the most common of whichis glycogen), glycosaminoglycans (mucopolysaccharides: hyaluronic and chondroitinsulfuric acids, heparin) and glycoproteins (mucins, i.e. mucus, and mucoids).
In order to detect carbohydrates in the cells of the body, a specific test is carried out - the CHIC reaction. Its essence is that the fabric is treated with iodic acid, and then fuchsin. And all aldehydes turn red. If it is necessary to isolate glycogen, then amylase is added to the reagents. Glycosaminoglycans and glycoproteins are stained with methylene blue. Parenchymal carbohydrate dystrophies are usually associated with impaired glycogen and glycoprotein metabolism.
Disruption of glycogen metabolism
Glycogen is the body's reserves for a “black hungry day”. It stores the main part of them in the liver and muscles and spends this energy very sparingly. The regulation of carbohydrate metabolism occurs through the neuroendocrine system. The main role is assigned, as usual, to the hypothalamic-pituitary system. It produces tropic hormones that control all other endocrine glands.
Violation of glycogen metabolism is an increase or decrease in its amount in tissues, as well as the appearance where it should not be. Most clearly, such changes are manifested in diabetes mellitus or hereditary glycogenoses. The pathogenesis of diabetes mellitus is quite well understood: the cells of the pancreas stop producing insulin in the required amount, and the energy reserves of the cells are quickly depleted, since glucose does not accumulate in the tissues, but is excreted frombody with urine. The body "reveals" its reserves, and first of all, parenchymal dystrophy of the liver develops. Light gaps appear in the nuclei of hepatocytes, and they become light. Therefore, they are also called "empty cores".
Hereditary glycogenoses are caused by a lack or absence of enzymes involved in the accumulation of glycogen. Currently, 6 such diseases are known:
- Gierke's disease;
- Pompe disease;
- McArdle disease;
- Hers disease;
- Forbes-Corey disease;
- Andersen's disease.
Their differential diagnosis is possible after a liver biopsy and the use of histoenzyme analysis.
Disruption of glycoprotein metabolism
These are parenchymal dystrophies caused by the accumulation of mucins or mucoids in tissues. Otherwise, these dystrophies are also called mucous or mucus-like, because of the characteristic consistency of the inclusions. Sometimes they accumulate on true mucins, but only substances similar to them, which can be compacted. In this case, we are talking about colloid dystrophy.
Tissue microscopy allows you to determine not only the presence of mucus, but also its properties. Due to the fact that the remnants of cells, as well as a viscous secret, prevent the normal outflow of fluid from the glands, cysts are formed, and their contents tend to become inflamed.
The causes of this type of dystrophy can be very different, but most often it is catarrhal inflammation of the mucous membranes. In addition, if a hereditary disease, the pathogenetic picturewhich fits well into the definition of mucosal degeneration. This is cystic fibrosis. The pancreas, intestinal tube, urinary tract, bile ducts, sweat and salivary glands are affected.
The resolution of this type of disease depends on the amount of mucus and the duration of its release. The less time has passed since the onset of the pathological process, the more likely it is that the mucosa will recover completely. But in some cases, there is desquamation of the epithelium, sclerosis and impaired function of the affected organ.
