Pathogenesis

Interrelation of Etiology and Pathogenesis

Pathogenesis is inextricably linked to etiology, as it represents the direct realization of the causative factor's action. Pathogenesis is based on the physiological reactions of the body's internal environment.

The most important property of pathogenetic factors is their relative constancy. This is because they are based on physiologically inherited mechanisms. As a result, the body responds stereotypically (consistently) even to completely different external stimuli.

• Example: The development of a malignant tumor can be triggered by many different chemical and physical carcinogens. There are many etiological causes, but the mechanism of cancer development (its pathogenesis) always remains the same.

At the same time, internal factors play a decisive role, particularly the organism's reactivity. It is the state of the pathogenetic mechanisms that determines whether the same etiological factor (e.g., a carcinogen) will cause disease in a specific individual or not.

Morphogenesis and Conditions for Recovery

Morphogenesis (from Greek morphe — form and genesis — development) is the set of mechanisms leading to morphological (structural) changes during the development of a pathological process. Morphogenesis and pathogenesis represent an inseparable dialectical unity and always develop in parallel.

The classic chain of disease development looks as follows:

1. The onset of the disease triggers a change in the structure of tissues or organs.
2. Following structural damage, the function of these structures becomes impaired.
3. Functional failures lead to the manifestation of visible clinical symptoms and syndromes.

There is a clear correlation: the deeper the morphological changes, the more severe the disease course, and vice versa. Three conditions must be met for a patient's complete recovery:

• Elimination of the pathogenic etiological factor.
• Liquidation of morphological damage (the repair process).
• Cessation of the disease development mechanisms.

Structure of Pathogenesis and Homeostasis

Structurally, pathogenesis consists of two key components:

• Genesis proper is the origin, the very initial moment of the pathological process's emergence.
• Pathokinesis is the further dynamics and staging of the disease development.

From the standpoint of biological expediency, absolutely all pathogenetic reactions have a homeostatic orientation. Their main goal is to use both physiological and pathological mechanisms to eliminate the root cause and return the parameters of the body's internal environment to normal (a state of health).

Since the number of general pathological reactions in the body is limited, pathogenetic mechanisms are characterized by stereotypy and typicality. They feature uniform development and similar morphological manifestations. Classical examples of such stereotyped processes are inflammation, the infectious process, and tumor growth.

Clinical Significance and Pathogenetic Therapy

Knowledge of the mechanisms of disease development is critical for therapy. In clinical reality, patients most often seek medical help at the stage of overt symptoms. The moment of disease onset (genesis) is subjectively and objectively elusive. For example, a gastric tumor makes itself known only upon reaching a certain size, and the exact time of its onset is unknown.

In such cases, when prevention of onset is impossible, the physician acts on the dynamics of the process (pathokinesis). This is the essence of pathogenetic therapy. It is effective even when the etiology is unknown. For example, in diabetes mellitus, the exact cause is not fully understood, but thoroughly studied metabolic disorders allow for successful treatment.

The stereotypy of the body's responses leads to the fact that identical pathogenetic signs can characterize different diseases. Thus, arterial hypertension can be an independent hypertensive disease or act as a symptom of atherosclerosis, kidney disease, or pheochromocytoma.

A variant of the pathogenetic approach is syndromological treatment. If the cause is unknown, but the patient is in critical condition (e.g., in a coma resulting from diabetes, malaria, or uremia), the physician focuses on eliminating the life-threatening syndrome. Targeting a specific link in pathogenesis can save a life before the etiology is clarified.

Class and exam questions

What else to study on this topic

• The role of the body's reactivity in the realization of etiological factors
• Morphogenesis: mechanisms of structural changes
• Homeostatic orientation of general pathological reactions
• Syndromological treatment as a variant of pathogenetic therapy
• Stereotyped pathological processes: inflammation, infection, tumor growth

Other topics in the "Introduction to Nosology" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.