An endotype is a subtype of a
health condition, which is defined by a distinct functional or
pathobiological mechanism. This is distinct from a
phenotype
In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological proper ...
, which is any observable characteristic or trait of a
disease
A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...
, such as development, biochemical or physiological properties without any implication of a mechanism. It is envisaged that
patient
A patient is any recipient of health care services that are performed by healthcare professionals. The patient is most often ill or injured and in need of treatment by a physician, nurse, optometrist, dentist, veterinarian, or other health c ...
s with a specific endotype present themselves within phenotypic clusters of diseases.
One example is
asthma
Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...
, which is considered to be a
syndrome
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". When a syndrome is paired ...
, consisting of a series of endotypes.
This is related to the concept of disease entity.
Disease entity
The main concept in
nosology
Nosology () is the branch of medical science that deals with the classification of diseases. Fully classifying a medical condition requires knowing its cause (and that there is only one cause), the effects it has on the body, the symptoms that ...
is the disease entity. Normally there are two ways to define a disease entity: Manifestational criteria and causal criteria.
* Manifestational criteria. These are a set of criteria based on signs, symptoms and laboratory findings that define a disease. They define a disease by its symptoms and medical findings.
* Causal criteria. These are a causal chain of events that defines the disease describing how it develops. They describe the disease by its
etiology
Etiology (pronounced ; alternatively: aetiology or ætiology) is the study of causation or origination. The word is derived from the Greek (''aitiología'') "giving a reason for" (, ''aitía'', "cause"); and ('' -logía''). More completely, e ...
.
Following
Fred Gifford,
these criteria lead one to view any disease entity in three different forms:
* Disease as symptoms: The disease is defined by the symptoms and
signs that it produces. In fact, it can be said that the disease is the collection of them. It is the classical way to define a disease or a condition.
* Disease as state: The disease is not defined by a set of symptoms but by the underlying state of the body, including pathological tissues, abnormal cells and any other general medical findings. This kind of definition allows the researchers to speak about
silent diseases, which cannot be considered as such by the previous definition. Proponents of this kinds of entity are for example
Rudolph Virchow
Rudolf Ludwig Carl Virchow (; or ; 13 October 18215 September 1902) was a German physician, anthropologist, pathologist, prehistorian, biologist, writer, editor, and politician. He is known as "the father of modern pathology" and as the founde ...
.
* Disease as a process: In the 20th century, a third concept of disease has appeared, based on the works of
Caroline Whitbeck in 1977. Whitbeck proposed that a disease may be defined by the clinical course of a set of untreated patients. She also argues that diseases are complex processes of which both clinical and underlying pathophysiological manifestations are proper parts (as contrasted with effects).
Following again F. Gifford, in fact each of the previous definitions can include the
aetiology
Etiology (pronounced ; alternatively: aetiology or ætiology) is the study of causation or origination. The word is derived from the Greek (''aitiología'') "giving a reason for" (, ''aitía'', "cause"); and ('' -logía''). More completely, e ...
or can be aetiologically agnostic. Other authors simply continue with the classification of Whitbeck, leaving just three kinds of definition (clinical, pathological and aetiological).
It is important to note that a real-world definition is normally a hybrid between these above kinds, and an endotype should use all three of the descriptors - including aetiology - to ensure
specificity.
See also
*
Heterogeneous condition
Notes
References
* {{Cite journal , last=Anderson , first=GP , s2cid=13161535 , title=Endotyping asthma: new insights into key pathogenic mechanisms in a complex, heterogeneous disease , journal=Lancet , date=20 September 2008 , volume=372 , issue=9643 , pages=1107–19 , doi=10.1016/s0140-6736(08)61452-x , pmid=18805339
Medical terminology