Etiologies

Etiology refers to the study of the causes or origins of diseases and other phenomena. In medicine, the etiologic factor is the agent or process responsible for producing a disease or condition. Identifying etiologies informs prevention, diagnosis, and treatment, and can influence public health strategies.

Etiologies can be classified in many ways. Broad categories include genetic (inherited mutations or chromosomal abnormalities), congenital (present at birth), infectious (pathogens such as bacteria, viruses, fungi), environmental and occupational (exposures), immune-mediated or autoimmune, metabolic, degenerative, nutritional, and iatrogenic (caused by medical treatment). Some conditions have multifactorial etiologies, and others are idiopathic when the cause remains unknown.

Determining etiology relies on clinical history, physical examination, and targeted testing, including laboratory assays, imaging, genetic testing, and epidemiologic analysis. In some cases, animal or cell models and trial interventions help establish causality. The term etiology is distinct from pathogenesis (the mechanisms by which a cause leads to disease) and from risk factors (factors that increase likelihood but are not necessarily causal).

Examples include peptic ulcer disease with Helicobacter pylori infection or NSAID use as etiologies; cystic fibrosis caused by CFTR gene mutations; and acquired liver injury related to alcohol or toxins. In epidemiology, identifying etiologies supports preventive measures and public health interventions.