Etiology

The etiology (from the Greek αἰτιολογία 'study of the cause') is the science focused on the study of causality. In medicine, pathogenesis refers to the origin of diseases. The word is used in philosophy, biology, criminal law, physics, and psychology to refer to the causes of phenomena.

History

Since the time of Hippocrates, doctors have been taught to begin medical histories by asking the patient:

• What's wrong with him?
• Since when?
• What do you attribute it to?

The doctor involves the patient, so that he expresses the cause, if he knows it, of his ills.

Throughout the history of medicine, physicians have debated whether the cause of a disease was a single factor or the result of a set of factors acting simultaneously. In the 19th century these two points of view were represented respectively by Pasteur and Bernard.

Bernard emphasized environmental factors, both external and internal. And he defended the idea of disease produced by a loss of internal balance (homeostasis) which generally involved the concurrence of a large number of factors.

Pasteur focused his efforts on clarifying the role played by bacteria in the appearance of a disease, linking different diseases with certain microbes. Pasteur demonstrated the correlation that exists between bacteria and certain diseases, and for this reason his theories had a decisive impact.

The position of Pasteur and his followers dominated the discussion, and as a result, the germ theory—according to which each disease was caused by a specific microbe—was quickly accepted by medical professionals.

The concept of scientific etiology was formulated by physician Robert Koch, who listed a series of Koch's postulates to test whether a given microbe caused a specific disease.

Advances in the field of biology in the 19th century were accompanied by the development of medical technology. New medical diagnostic instruments, including the stethoscope and blood pressure devices, were invented, and surgical technology became more sophisticated.

Well into the XX century, it is recognized that the cause of diseases is multiple where the determinants of the health that are the environment, the agent and the host.

Etiology in medicine

Etiology in the field of medicine refers mainly to the study of the causes of diseases

The three elements necessary for a disease to develop are:

• The environment.
• The agent.
• The guest.

These three "elements" by themselves they do not "cause" a problem. It is the concurrence of all three, in time and space, that results in disease. When the cause or causes of a disease are known, it facilitates the investigation of a specific treatment, or failing that, a treatment to improve the patient's quality of life.

Four basic types of factors are considered to influence the causes of disease:

• Predisposing: age, sex, previous illness or others can create greater sensitivity to a disease.
• Facilitators: low income, malnutrition, poor housing conditions, among others, can promote the development of certain diseases.
• Dismantling: Exposure to a pathogen-caused disease-can precipitate its development;
• Potential: repeated exposure to a pathogen can aggravate a disease already present.

Types of diseases

According to their etiopathogenesis (according to the cause and the consequent pathophysiology) diseases can be classified as:

• Endogenous diseases (attributable to guest alteration):

- Genetics

- Congenital

- Nutritional

- Metabolics

- Degenerative

- Autoimmune

- Inflammaries

- Endocrinas

- Mental

• Exogenous diseases (attributable to the effect of direct action by the agent on the host):

- Infectious

- Parasitic

- Venéreas

- Toxic

- Traumatics

- Allergies

- Iatrógens

• Environmental diseases (attributable to the effects of the environment and the agent - together - on the host):

- Environmental

- Professionals

- Mecanopostural

- For external reasons

• Multifactorial etiology diseases:

- Neopletic

- Development

- Idiopathic

- Psychosomatics

Currently, several of the health conditions that cause the different types of diseases are codified in the International Classification of Diseases, Tenth Version. Said classification is based on a wide variety of signs, symptoms, abnormal findings, complaints, social circumstances and external causes that produce damage and/or disease.