Etiology of internal diseases

Nature of disease and reactivity

According to E.M. Tareev's concept, any disease is a response reaction of the organism to the impact of various factors, as well as a consequence of impaired adaptability (adaptation) to changed environmental conditions. Pathogenesis is always based on the close interaction between the environment and reactivity of the organism.

Factors causing diseases are traditionally divided into two large groups:

• External factors: dietary habits, unfavorable environmental conditions, climatic conditions, and exposure to infectious agents.
• Internal factors: congenital developmental disorders and genetic abnormalities.

Internal factors often play a decisive role. The same etiological factor causes severe disease in one person while passing unnoticed in another. This means that the etiological significance of any external impact directly depends on the initial state of internal pathogenetic mechanisms and the reactivity of a specific patient.

Interrelation of Etiology and Pathogenesis

The basis of pathogenesis is formed by the physiological reactions of the body's internal environment. These pathogenetic mechanisms are based on hereditarily fixed physiological processes, which is why they are relatively constant.

The main principle of the internal environment's reaction is stereotypy. The organism reacts identically (constantly) even to influences that are completely different in nature.

A striking example of such a stereotyped response is the development of malignant tumors. Cancer can be triggered by a multitude of different chemical substances or physical radiations (i.e., there are many etiological causes), but the mechanism of its development (pathogenesis) always remains the same. The internal environment determines this stereotypy and homeostatic orientation of reactions dialectically linked to the cause of the disease.

Hemorrhagic syndrome: three levels of etiology

Let us examine the diversity of etiological factors using the example of hemorrhagic syndrome. This is pathological bleeding manifested by external or internal hemorrhages.

The causes of bleeding are divided into three main groups (pathogenetic levels):

1. Platelet link. Associated with platelet pathology. It can manifest as quantitative changes — thrombocytopenias (a classic example is Werlhof's disease), or qualitative changes — thrombocytopathies (dysfunction of the platelets themselves).
2. Coagulation link. Associated with disorders in the blood coagulation system. Most often, this is a deficiency of certain clotting factors (for example, in hemophilia).
3. Vascular link. Caused by damage to the vessel wall and changes in its permeability. This includes hereditary telangiectasia (Rendu-Osler disease) and hemorrhagic vasculitis (Schönlein-Henoch purpura).

Pathogenetic and syndromic treatment

In clinical practice, a physician does not always know the exact cause of a disease. However, knowledge of the mechanisms of development (pathogenesis) makes it possible to predict the course of the disease and provide effective therapy. Such treatment is called pathogenetic.

For example, the etiology of diabetes mellitus is not fully understood, but thoroughly studied metabolic disorders make it possible to treat patients successfully.

Due to the stereotypy of reactions, identical pathogenetic signs can occur in different nosologies. Thus, arterial hypertension can be a manifestation of primary hypertension or merely a symptom of other conditions: kidney disease, atherosclerosis, or an adrenal tumor (pheochromocytoma).

When the cause is unknown and severe manifestations come to the fore, syndromic treatment is used.

• Example: A patient is in a coma. Coma can be a stage of diabetes mellitus, severe malaria, or uremia.
• Tactic: The physician directs efforts to eliminate this life-threatening syndrome without waiting to determine the cause.

In essence, this is a variant of pathogenetic treatment that allows saving the patient's life before the etiology is finally clarified.

Class and exam questions

What else to study on this topic

• Mechanisms of formation of the body's reactivity
• Differential diagnosis of hemorrhagic syndrome
• Werlhof's disease: etiology and manifestations
• Symptomatic arterial hypertension in pheochromocytoma and renal pathology
• Types of coma (diabetic, uremic, malarial) and their pathogenesis

Other topics in the "Additional Topics" section

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