In medicine, disease pathogenesis is a term used to refer to the origin and development of a disease. The study of disease pathogenesis, which is more often referred to simply as pathogenesis, forms a sub-branch of the wider fields of pathobiology and pathology. While pathobiology and pathology refer to the general biology, development, and progress of a disease, pathogenesis usually focuses on the factors that lead to the initial origin of the disease.
In the case of many diseases, multiple factors affect the disease pathogenesis. For example, an individual may have a genetic predisposition to a disease, but the disease may not actually occur unless certain environmental factors are also present. Similarly, some kinds of infectious disease are often fought off by an infected individual without any symptoms ever appearing. Such infections might cause disease, for example, only if the bacteria or virus that causes it are present, and at the same time the immunity of the infected person is weakened by malnutrition or a disorder of the immune system.
There are many different types of disease pathogenesis. These include invasion of the body by viruses or bacteria, inflammation as a response to chemicals, physical trauma, the presence of cancerous cells, and many different kinds of genetic disorders. As there are so many possible origins of disease, doctors and researchers who study disease pathogenesis often specialize in one particular field of pathogenesis.
Some specialist fields of pathogenesis include hematopathology, clinical microbiology, genetics, and immunopathology. Hematopathology relates to abnormalities of the blood, the bone marrow, and the lymphatic system, and how such abnormalities may lead to disease. In clinical microbiology, the study of pathogenesis includes examining how bacteria and viruses spread and multiply. Genetics has a very important bearing on pathogenesis, as a great number of diseases originate partly, or wholly, as a result of a particular gene, a mutation, or an abnormality in the genetic material of the patient. Immunopathology is of particular importance in the disease pathogenesis of infectious diseases, as it relates to the immune system, including how immunity weaknesses may allow a virus or bacterium to take hold and cause a disease.
While some doctors specialize in one of the above fields of pathogenesis, other doctors and researchers may work in multiple fields. This is often the case with individuals who are studying pathogenesis as it relates to a specific disease. In the case of some cancers, understanding the full disease pathogenesis may include genetic, infectious, chemical, and immunological factors.