What is trophics and why is it impaired?
Trophics ensures proper metabolism and structural organization of tissues, which is necessary for them to perform their specialized functions. It is maintained at two levels:
- Cellular: through genetically determined autoregulation and the structure of the cell itself.
- Extracellular: via transport systems (blood, lymph) and integrative systems (nervous, endocrine, humoral).
If these mechanisms fail, dystrophy develops. The etiology of the process is extremely diverse. Causes may include hypoxia, exposure to toxins (including microbial) and drugs, physical and chemical agents, viruses, as well as nutritional imbalance. Dystrophies often occur against the background of nervous and endocrine system disorders, changes in the composition of blood or urine, and due to genetic enzyme defects (enzymopathies).
Morphologically, dystrophy manifests in various ways:
- Substances accumulate in tissues above normal levels.
- The physicochemical properties of habitual compounds are altered.
- Common substances appear in atypical locations.
- Completely new substances emerge that are not normally present (inside cells, in the stroma, intercellular matrix, or vascular walls).
Classification principles
The pathological process is systematized according to several key criteria.
By type of metabolic disorder:
- Protein.
- Lipid.
- Carbohydrate.
- Mineral.
- Fluid.
- Mixed.
By predominant localization:
- Parenchymal (disorders within cells).
- Stromal-vascular (disorders in the intercellular matrix and vascular walls).
- Mixed.
By genetic factors:
- Hereditary: occur due to a genetic enzyme defect. Metabolic products are not broken down, forming storage diseases (thesaurismoses).
- Acquired: associated with secondary enzymopathies, often proceeding against the background of impaired substance transport or energy supply.
Also, depending on the prevalence of the process, general and local dystrophies are distinguished.
Morphogenetic mechanisms of development
There are four basic pathways through which morphological changes develop in dystrophies:
- Infiltration. Excessive penetration of substances into a cell or intercellular matrix with their subsequent accumulation. This occurs either due to an excess of a substance in the inflowing fluid or a lack of enzymes for its processing. Examples: protein accumulation in renal tubular epithelium in proteinuria; lipid accumulation in the myocardium in diphtheria (due to disruption of carnitine shuttle transport); deposition of non-excreted exogenous particles (e.g., carbon).
- Decomposition (phanerosis). Breakdown of complex chemical compounds or cellular ultrastructures, leading to the accumulation of breakdown products. Example: fibrinoid changes in connective tissue in rheumatic diseases due to the breakdown of polysaccharide-protein complexes.
- Transformation. Chemical conversion of one type of substance into another. Example: conversion of carbohydrates into fats against the background of diabetes mellitus.
- Perverted synthesis. Formation of completely new, abnormal substances in tissues. Example: synthesis and deposition of amyloid in the intercellular space.
Features of the course and outcomes
Morphogenetic mechanisms rarely work in isolation: they can combine or transition into one another (e.g., infiltration is often a preceding stage to decomposition). Each specific organ is characterized by its own typical damage mechanism due to its structural and functional features — this phenomenon is called orthology (from Greek orthos — typical).
Among the morphological types, granular, hyaline-droplet, hydropic, and horny dystrophies are distinguished (the mechanism of the latter differs from the rest).
If the process becomes irreversible, the cell dies. The type of developing necrosis (focal or total) directly depends on the preceding pathology:
- Hyaline-droplet dystrophy leads to coagulative necrosis.
- Hydropic dystrophy terminates in colliquative necrosis (ballooning degeneration).
Briefly: answers to topical questions
What types of parenchymal protein dystrophies (dysproteinoses) are distinguished in pathological anatomy?
Pathological anatomy distinguishes four main morphological types of parenchymal protein dystrophies. These include:
- Granular dystrophy — characterized by hyperplasia of cell ultrastructures or their swelling.
- Hyaline-droplet dystrophy — manifests as the formation of large eosinophilic droplets in the cytoplasm.
- Hydropic dystrophy — accompanied by fluid accumulation and vacuole formation in the cytoplasm.
- Horny dystrophy — the development mechanism of which differs from previous types.
What sequential stages are distinguished in the development of stromal-vascular protein dystrophies?
During the development of stromal-vascular protein dystrophies, three sequential stages of connective tissue disorganization are distinguished. The dynamics of the process include the following stages:
- Mucoid swelling — the initial stage, characterized by the accumulation of glycosaminoglycans in the ground substance.
- Fibrinoid swelling — the next stage, in which organ function decreases or ceases.
- Hyalinosis — the final stage, caused by the destruction of fibrous structures and increased vascular permeability.
Amyloidosis is distinguished separately; it is characterized by the formation of an abnormal fibrillar protein and is not part of this sequential chain.
What specific diseases belong to hereditary storage diseases (thesaurismoses)?
Hereditary storage diseases (thesaurismoses) include systemic lipidoses arising from genetic enzyme deficiencies. This group includes the following specific diseases:
- Cerebroside lipidosis — Gaucher's disease, characterized by the accumulation of abnormal lipid and carbohydrate complexes.
- Sphingomyelin lipidosis — Niemann-Pick disease.
- Ganglioside lipidosis — Tay-Sachs disease.
- Generalized ganglioside lipidosis — Norman-Landing disease.
In these pathologies, metabolic products are not metabolized, but accumulate in the cells of the liver, spleen, bone marrow, and central nervous system.
To easily remember the 4 mechanisms of dystrophy development, use the mnemonic IDTI: Infiltration, Decomposition, Transformation, Inverted synthesis.
Class and exam questions
What are thesaurismoses?
These are storage diseases. They develop in hereditary dystrophies when, due to a genetic enzyme defect (enzymopathy), metabolic products are not metabolized but are instead stored in tissues.
How does infiltration differ from perverted synthesis?
During infiltration, normal substances accumulate (either coming from outside or not metabolized due to enzyme deficiency), whereas in perverted synthesis, the cell begins to produce abnormal compounds that do not normally occur (e.g., amyloid).
What does the term «orthology» mean in the context of dystrophies?
This concept means that in specific organs and tissues, due to their unique structure and functions, one single morphogenetic mechanism of dystrophy—the one most typical for them—predominates.
What else to study on this topic
- Parenchymal protein dystrophies: granular, hyaline-droplet, hydropic
- Stromal-vascular dysproteinosis and mechanisms of amyloid formation
- Morphological features of fatty dystrophies of the myocardium and liver
- Disorders of carbohydrate metabolism using diabetes mellitus as an example
- Differences between coagulation and liquefactive necrosis as outcomes of dystrophies
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