Sometimes in clinical practice there is such a thing as parenchymal dystrophy. Pathological anatomy refers them to metabolic disorders in cells. In simple terms, the organ disrupts the process of nutrition and accumulation of nutrients, 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, self-regulation disorders of the cell with energy deficiency, fermentopathy, discirculatory disorders (blood, lymph, interstitium, intercellular fluid), endocrine and cerebral dystrophies are distinguished.
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 failure in the enzyme systems of the body;
- decomposition, or phanerosis, is the breakdown of intracellular structures, which leads to metabolic disturbances and the accumulation of under-oxidized metabolic products;
- perverse synthesis of substances that normally the cell does not reproduce;
- the transformation of nutrients entering the cell to build one kind of final product (proteins, fats or carbohydrates).
Classification
Pathomorphologists distinguish the following types of parenchymal dystrophies:
1. Depending on morphological changes:
- purely parenchymal;
- stromal vascular;
- mixed.
2. By the type of accumulated substances:
- protein or dysproteinoses;
- fatty or lipidoses;
- carbohydrate;
- mineral.
3. The prevalence of the process:
- systemic;
- local.
4. By time of appearance:
- acquired;
- congenital.
These or other parenchymal dystrophies determine the pathological anatomy not only by the damaging agent, but also by the specificity 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 that occurs in the cell, but only part of the clinical syndrome, which covers the morphological and functional insufficiency of a particular organ.
Dysproteinosis
The human body for the most part consists of proteins and water. Protein molecules are a component 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 collocation. Protein parenchymal dystrophies include hyaline droplet, hydropic, horn and granular dystrophies. The first three will be described 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 grows, becomes loose, dull. That is why granular dystrophy is also called dull swelling. But scientists have doubts that this is parenchymal dystrophy. The pathology of this process is such that compensatory enlarged cell structures can be taken for grains as a response to functional stress.
Hyaline droplet degeneration
With this type of dystrophy , large hyaline drops appear in the cells, which eventually merge with each other and fill the entire inner space of the cell, displacing the 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, the destruction of all cellular elements is detected. This phenomenon appears if a patient develops vacuolar-lysosomal insufficiency, which leads to a decrease in protein reabsorption from primary urine. Most often, this pathology occurs with nephrotic syndrome. The most common diagnoses of such patients are glomerulonephritis and renal amyloidosis. The appearance of the organ with hyaline droplet dystrophy does not change.
In cells, the situation is somewhat different. During microscopy, they find Mallory bodies, consisting of fibrils and alcohol hyaline. Their appearance is associated with Wilson-Konovalov disease, alcoholic hepatitis, as well as with 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 rest 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 a clear liquid content. The nucleus is displaced or lysed, other structures are eliminated. Ultimately, the cell is a “balloon” filled with water. Therefore, hydropic dystrophy is sometimes called balloon.
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 cells die. The causes of such chemical changes can be glomerulonephritis, diabetes mellitus, renal amyloidosis. In the liver, viral and toxic hepatitis contribute to cell change. Hydropic dystrophy on the skin can be caused by smallpox virus.
This pathological process ends with focal or total necrosis, so the morphology and function of organs quickly deteriorates.
Horny 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 either local or total.
The causes of this type of disease can be violations of the ectodermal germ in the process of embryogenesis, chronic inflammatory tissue changes, viral infections and a lack of vitamins.
If treatment is started immediately after the onset of the first symptoms, then the tissue can still recover, but in advanced cases, recovery is no longer possible. Long-existing areas of horny dystrophy can degenerate into skin cancer, and congenital ichthyosis is incompatible with the life of the fetus.
Hereditary Dystrophies
Hereditary parenchymal dystrophies occur due to congenital fermentopathies. These diseases are also called accumulation diseases, because due to metabolic disorders, metabolic products accumulate in the cells and body fluids, poisoning it. The most famous representatives of this group are phenylketonuria, tyrosinosis, and cystinosis.
Target organs for phenylketonuria are the central nervous system, muscles, skin and fluids (blood, urine). Metabolic products with tyrosinosis accumulate in the cells of the liver, kidneys and bones. Cystinosis also affects the liver and kidneys, but besides them, the spleen, eyeballs, bone marrow, lymphatic system and skin suffer.
Lipidosis
Lipids are contained in each cell, they can be both separately and in combination with proteins and can be structural units of the cell membrane, as well as other ultrastructures. In addition, glycerol and fatty acids are located in the cytoplasm. In order to detect them in the 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 in 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.
Fat parenchymal myocardial dystrophy begins with the appearance of very small droplets of fat in myocytes, the so-called. dusty obesity. If the process does not stop at this stage, then over time the droplets merge and become larger until they occupy the entire cytoplasm. At the same time, the organelles disintegrate, the striation of the muscle fibers disappears. The disease locally manifests itself 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 be made only under a microscope, but over time, the heart grows due to the stretching of the chambers, its walls become thin and flabby, with a cut of the myocardium dirty yellow stripes are visible. Pathophysiologists have come up with a name for this organ: “tiger heart”.
Fatty degeneration of parenchymal organs develops according to three main mechanisms.
- Increased intake of free fatty acids in myocardial cells.
- Violation of fat metabolism.
- The breakdown of lipoprotein structures within 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 recover over time. But if the process is severely launched, then everything ends with the death of the tissue and organ. Clinicians distinguish the following diseases associated with the accumulation of fats in cells:
- Gaucher disease;
- Tay-Sachs disease;
- Nimann-Peak disease and others.
Carbohydrate Dystrophy
All carbohydrates that are in the body can be divided into polysaccharides (the most common of which is glycogen), glycosaminoglycans (mucopolysaccharides: hyaluronic and chondroitin sulfuric acids, heparin) and glycoproteins (mucins, i.e. mucus, and mucoids).
In order to identify carbohydrates in the cells of the body, they conduct a specific test - the SIC reaction. Its essence is that the tissue is treated with iodic acid, and then with fuchsin. And all the aldehydes turn red. If glycogen needs to be isolated, then amylase is added to the reagents. Glycosaminoglycans and glycoproteins are stained with methylene blue. Parenchymal carbohydrate dystrophies are associated, as a rule, with a violation of the exchange of glycogen and glycoproteins.
Glycogen exchange disorder
Glycogen is the body’s reserves for a “hungry black day”. He stores the bulk of them in the liver and muscles and consumes 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 glands of internal secretion.
A 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 fairly well understood: pancreatic cells 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 in the urine. The body "opens" its reserves, and parenchymal dystrophy of the liver primarily 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:
- Girke's disease ;
- Pompe disease ;
- McArdle's 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 the tissues. Otherwise, these dystrophies are also called mucous or mucus-like, due to the characteristic consistency of inclusions. Sometimes they accumulate on true mucins, but only substances similar to them that can condense. In this case, we are talking about colloid dystrophy.
Microscopy of the tissue allows us to determine not only the fact of the presence of mucus, but also its properties. Due to the fact that the remnants of the cells, as well as a viscous secretion interferes with the normal outflow of fluid from the glands, cysts form, 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 there is a hereditary disease, the pathogenetic picture of which fits well with the definition of mucous dystrophy. 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 excretion. The less time has passed from the beginning of the pathological process, the more likely that the mucous membrane will fully recover. But in some cases, desquamation of the epithelium, sclerosis and impaired function of the affected organ are observed.