etiologie

Etiology, or étiologie in French, is the study of the causes or origins of a disease or condition. In medicine, etiology denotes the specific factor or combination of factors that is responsible for the disease, as distinct from its mechanisms of development (pathogenesis). Causes may be genetic, infectious, environmental, nutritional, immune-mediated, toxic, or a combination of these.

Causes can be categorized as necessary, sufficient, or contributory. A necessary cause is present for disease to occur, but not all diseases have a single necessary cause. A sufficient cause alone may produce disease, but most diseases have multifactorial etiologies, with several factors acting together. Etiologies are also described as congenital (present at birth) or acquired later in life.

Common etiologic categories include genetic disorders (eg, cystic fibrosis, Huntington disease); infectious agents (bacteria, viruses); environmental exposures (tobacco smoke, air pollutants); immune or autoimmune processes; nutritional deficiencies or excesses; toxins and medications (iatrogenic causes); and physical factors such as trauma. In many cases, the etiology remains unknown (idiopathic), or is classified as multifactorial.

Diagnosis of etiology relies on patient history, clinical examination, epidemiology, and targeted laboratory or imaging tests to identify a likely cause and exclude alternatives. Understanding etiology informs prognosis, prevention, and treatment, and is an active area in research as new causal factors are discovered.