Examples of the first-mentioned type are that Turner syndrome and DiGeorge syndrome are still often called by the "syndrome" name despite that they can also be viewed as disease entities and not solely as sets of signs and symptoms. Predisease
Predisease is a subclinical or prodromal vanguard of a disease. Prediabetes and prehypertension are common examples. The nosology or epistemology of predisease is contentious, though, because there is seldom a bright line differentiating a legitimate concern for subclinical/prodromal/premonitory status (on one hand) and conflict of interest–driven disease mongering or medicalization (on the other hand). Identifying legitimate predisease can result in useful preventive measures, such as motivating the person to get a healthy amount of physical exercise, but labeling a healthy person with an unfounded notion of predisease can result in overtreatment, such as taking drugs that only help people with severe disease or paying for drug prescription instances whose benefit–cost ratio is minuscule (placing it in the waste category of CMS "waste, fraud, and abuse" classification). Three requirements for the legitimacy of calling a condition a predisease are:
a truly high risk for progression to disease – for example, a pre-cancer will almost certainly turn into cancer over time
actionability for risk reduction – for example, removal of the precancerous tissue prevents it from turning into a potentially deadly cancer
benefit that outweighs the harm of any interventions taken – removing the precancerous tissue prevents cancer, and thus prevents a potential death from cancer.
Types by body system
Mental
Mental illness is a broad, generic label for a category of illnesses that may include affective or emotional instability, behavioral dysregulation, cognitive dysfunction or impairment. Specific illnesses known as mental illnesses include major depression, generalized anxiety disorders, schizophrenia, and attention deficit hyperactivity disorder, to name a few. Mental illness can be of biological (e.g., anatomical, chemical, or genetic) or psychological (e.g., trauma or conflict) origin. It can impair the affected persons ability to work or study and can harm interpersonal relationships. The term insanity is used technically as a legal term. Organic
An organic disease is one caused by a physical or physiological change to some tissue or organ of the body. The term sometimes excludes infections. It is commonly used in contrast with mental disorders. It includes emotional and behavioral disorders if they are due to changes to the physical structures or functioning of the body, such as after a stroke or a traumatic brain injury, but not if they are due to psychosocial issues. Stages
In an infectious disease, the incubation period is the time between infection and the appearance of symptoms. The latency period is the time between infection and the ability of the disease to spread to another person, which may precede, follow, or be simultaneous with the appearance of symptoms. Some viruses also exhibit a dormant phase, called viral latency, in which the virus hides in the body in an inactive state.