Evolution of views: from causalism to reactivity
Historically, two polar directions formed in medicine. The first is causalism (from Latin causalis — causal). In the 19th century, Claude Bernard put forward the idea that every disease has its own cause, but certain objective conditions are necessary for it to manifest. Later, in the 1870s, against the background of the rapid development of microbiology and Louis Pasteur's discoveries, monocausalism emerged. Its essence was that any disease has only one cause—bacteria—while environmental conditions were considered secondary and insignificant.
However, monocausalism soon faced a severe crisis. It turned out that the mere presence of a microorganism in the body is not enough for a disease to develop. The phenomena of bacillary carriage and dormant infection were discovered. It became obvious that different people react completely differently to the same pathogen under identical conditions. This led to a crucial consequence: the focus of scientists' attention shifted to studying the reactivity of the organism, which ultimately gave rise to the study of allergy.
Conditionalism and denial of the cause
As a reaction to the obvious flaws of causalism, a second direction arose — conditionalism (from Latin condicio — condition). Its founder was the 19th-20th century German philosopher Max Verworn.
The essence of this theory lay in the complete denial of the very cause of diseases. Conditionalists recognized exclusively the conditions of their origin. Moreover, the specifics of this approach were such that it predominantly considered subjective conditions, while crucial socio-economic factors were often simply excluded from the analysis.
Verworn's main tenets stated that the concept of "causality" should be entirely excluded from scientific thinking and replaced by abstract mathematical concepts. Disease, in his view, is associated with a complex of various conditions. Verworn believed that a doctor should know three basic things: the conditions of health (to maintain them) and the conditions for the development of diseases (to prevent or treat them).
Modern concepts of disease origin
Modern medicine has found a balance and views disease as the result of a complex interaction between cause and conditions. The mechanism of pathological development is triggered when, under the influence of a cause in specific conditions, homeostasis—the organism's equilibrium with the external environment—is disrupted. The essence of this process lies in the insufficiency of the organism's adaptability (adaptation) to environmental factors.
Living conditions affecting this process are divided into two groups:
- External environment: social, geographical, biological, and physical factors.
- Internal environment: conditions originating within the organism itself (e.g., heredity and constitution).
Interestingly, in cases where the true cause of a disease is still unknown, modern medicine is forced to rely on the tenets of conditionalism, focusing specifically on the conditions of pathological development.
Clinical significance of etiology
A key postulate of modern pathological anatomy: there can be no disease without a cause. It is the cause that determines the specificity (qualitative features) of a particular disease. Causes can be external (environmental factors) and internal (genetic defects, congenital malformations).
To date, etiology is well studied for most infectious and endocrine diseases, as well as injuries. However, a vast layer of diseases with an undetermined etiology remains: psychiatric disorders, malignant tumors, atherosclerosis, sepsis, sarcoidosis.
Knowledge of etiology is critically important for clinical practice:
- Etiological treatment: aimed at the complete elimination of the cause. This is the most effective approach if the cause is known.
- Role of conditions: understanding the conditions explains individual patient reactivity (why some get sick under the same exposure while others do not).
- Treatment without knowing the cause: even if the etiology is unknown, successful treatment is possible by influencing the mechanisms of development (pathogenesis). A striking example is appendicitis: its clinical presentation, course, and outcomes are well known, surgical treatment is well established, but the exact etiology remains unestablished to this day.
Briefly: answers to topical questions
What types of etiological factors (causes) are distinguished in general pathology?
In general pathology, etiological factors are classified as external and internal.
- External — environmental factors: social, geographical, biological, and physical; chemical factors include exogenous and endogenous substances.
- Internal — disorders within the organism itself, including genetic defects and congenital malformations.
According to the nature of the damaging effect, they are distinguished as:
- Physical — mechanical trauma, radiation energy.
- Chemical — exogenous (acids, alkalis, drugs, alcohol, nicotine, heavy metal salts) and endogenous (metabolic products in renal and hepatic failure).
- Biological — infectious agents, antigens, and autoantibodies.
What types of organism reactivity exist?
Organism reactivity is classified by biological properties, adequacy of response, and manifestations in infections. Depending on biological properties:
- Species reactivity — determined by the characteristics of a particular species.
- Group reactivity — depends on group affiliation (age, sex, constitutional).
By adequacy of response:
- Physiological reactivity — an adequate response with adaptive significance.
- Pathological reactivity — an inadequate reaction that reduces adaptive capabilities.
In infectious processes, the following are distinguished:
- Allergy — an increased reaction to a pathogen.
- Hyperergia — a manifestation of allergy in the form of hypersensitivity.
- Hypoergia — decreased reactivity.
- Anergy — absence of reaction (positive or negative).
What specifically belongs to biological environmental factors in etiology?
Biological environmental factors include infectious agents, antigens, and autoantibodies.
Pathogens of infectious diseases include:
- bacteria;
- viruses;
- fungi;
- protozoa;
- helminths;
- prions.
Biological factors also include microorganism cell components, predominantly proteinaceous, as well as foreign proteins, including those part of vaccines.
What is the role of various constitutional types in disease predisposition?
Constitutional type acts as a risk factor and indicates the probability of developing specific pathological processes.
- Asthenic type — predisposes to kidney and gallstones, atherosclerosis, obesity, and arterial hypertension. With high height measurements, Marfan syndrome is possible (risk of aortic defects).
- Hypersthenic type — in men, causes a predisposition to ischemic heart disease (IHD) and arterial hypertension.
- Lymphatic-hypoplastic and exudative-catarrhal constitutions are risk factors for the development of primary paratrophy.
In addition, predisposition to somatic disorders is considered a manifestation of psychophysiological constitution.
To avoid confusing historical schools: Causalism looks for the Root (cause), while Conditionalism looks for the Context (conditions).
Class and exam questions
Can a disease occur without a cause?
No. Modern medicine postulates that there is no disease without a cause. It is the root cause that determines the specificity and qualitative characteristics of any disease.
Why did the theory of monocausalism fail?
It turned out that the mere presence of a microbe is not enough for a disease to develop. The phenomena of bacilli carriage and latent infection were discovered, proving that different people react differently to the same pathogen.
Is it possible to cure a patient if the etiology of their disease is unknown?
Yes, this is possible. If the cause is unclear, the physician targets pathogenesis—the mechanisms of disease development. A classic example is appendicitis, which is successfully treated surgically, although its exact cause is still not established.
What else to study on this topic
- Mechanisms of homeostasis disruption and adaptation failure
- The role of organism reactivity in the development of infectious diseases
- Internal causes of diseases: genetic defects and congenital malformations
- Diseases with unknown etiology: theories of tumor and atherosclerosis pathogenesis
- Pathogenesis as the basis of treatment when etiology is unknown
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