pathogenesis of a disease is the biological mechanism (or mechanisms) that leads to a diseased state. The term can also describe the origin and development of the disease, and whether it is acute, chronic, or recurrent. The word comes from the Greek pathos ("suffering", "disease") and ? genesis ("creation").
Types of pathogenesis include
microbial infection, inflammation, malignancy and tissue breakdown. For example, bacterial pathogenesis is the mechanism by which bacteria cause infectious illness.
Most diseases are caused by multiple processes. For example, certain
cancers arise from dysfunction of the immune system ( skin tumors and lymphoma after a renal transplant, which requires immunosuppression).  
The pathogenic mechanisms of a disease (or condition) are set in motion by the underlying causes, which if controlled would allow the disease to be
prevented. Often, a potential cause is identified by  epidemiological observations before a pathological link can be drawn between the cause and the disease. The pathological perspective can be directly integrated into an epidemiological approach in the interdisciplinary field of molecular pathological epidemiology. Molecular pathological epidemiology can help to assess pathogenesis and causality by means of linking a potential risk factor to molecular pathologic signatures of a disease.  Thus, the  molecular pathological epidemiology paradigm can advance the area of causal inference.
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