A syndrome is a set of medical signs and symptoms which are correlated with each other and often associated with a particular disease or disorder. The word derives from the Greek σύνδρομον, meaning "concurrence". In some instances, a syndrome is so closely linked with a pathogenesis or cause that the wordssyndrome, disease, and disorder end up being used interchangeably for them. This is especially true of inherited syndromes. For example, Down syndrome, Wolf–Hirschhorn syndrome, and Andersen syndrome are disorders with known pathogeneses, so each is more than just a set of signs and symptoms, despite the syndrome nomenclature. In other instances, a syndrome is not specific to only one disease. For example, toxic shock syndrome can be caused by various toxins; premotor syndrome can be caused by various brain lesions; and premenstrual syndrome is not a disease but simply a set of symptoms. If an underlying genetic cause is suspected but not known, a condition may be referred to as a genetic association. By definition, an association indicates that the collection of signs and symptoms occurs in combination more frequently than would be likely by chance alone. Syndromes are often named after the physician or group of physicians that discovered them or initially described the full clinical picture. Such eponymous syndrome names are examples of medical eponyms. Recently, there has been a shift towards naming conditions descriptively rather than eponymously, but the eponymous syndrome names often persist in common usage.
Usage
General medicine
In medicine, a broad definition of syndrome is used, which describes a collection of symptoms and findings without necessarily tying them to a single identifiable pathogenesis. The more specific definition employed in medical genetics describes a subset of all medical syndromes.
The most important psychopathological syndromes were classified into three groups ranked in order of severity by German psychiatrist Emil Kraepelin. The first group, which includes the mild disorders, consists of five syndromes: emotional, paranoid, hysterical, delirious, impulsive. The second, intermediate, group includes two syndromes: schizophrenic syndrome and speech-hallucinatory syndrome. The third includes the most severe disorders, and consists of three syndromes: epileptic, oligophrenic and dementia. In Kraepelin's era, epilepsy was viewed as a mental illness; Karl Jaspers also considered "genuine epilepsy" a "psychosis"., and described "the three major psychoses" as schizophrenia, epilepsy, and manic-depressive illness.
Medical genetics
In the field of medical genetics, the term "syndrome" is traditionally only used when the underlying genetic cause is known. Thus, Trisomy 21 is commonly known as Down syndrome. Until 2005, CHARGE syndrome was most frequently referred to as "CHARGE association". When the major causative gene for the condition was discovered, the name was changed. The consensus underlying cause of VACTERL association has not been determined, and thus it is not commonly referred to as a "syndrome".
Other fields
In biology, "syndrome" is used in a more general sense to describe characteristic sets of features in various contexts. Examples include behavioral syndromes, as well as pollination syndromes and seed dispersal syndromes. In orbital mechanics and astronomy, Kessler syndrome refers to the effect where the density of objects in low Earth orbit is high enough that collisions between objects could cause a cascade in which each collision generates space debris that increases the likelihood of further collisions. A China Syndrome is a fictional scenario where a nuclear meltdown melts through a reactor containment vessel and then all the way through the earth to the opposite side.
Naming
There is no set common convention for the naming of newly identified syndromes. In the past, syndromes were often named after the physician or scientist who identified and described the condition in an initial publication, these are referred to as "eponymous syndromes". In some cases, diseases are named after the patient who initially presents with symptoms, or their home town. There have been isolated cases of patients being eager to have their syndromes named after them, while their physicians are hesitant. When a syndrome is named after a person, there is some difference of opinion as to whether it should take the possessive form or not. North American usage has tended to favor the non-possessive form, while European references often use the possessive. Even in Europe, there has been a trend away from the possessive form, over the period between 1970 and 2008.
History
, in The Canon of Medicine, pioneered the idea of a syndrome in the diagnosis of specific diseases. The concept of a medical syndrome was further developed in the 17th century by Thomas Sydenham.
Underlying cause
Even in syndromes with no known etiology, the presence of the associated symptoms with a statistically improbable correlation normally leads the researchers to hypothesize that there exists an unknown underlying cause for all the described symptoms.
