A heterogeneous medical condition or heterogeneous disease is a medical term referring to a

medical condition A disease is a particular abnormal condition that negatively affects the structure or function (biology), function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medica ...

with several

etiologies Cause, also known as etiology () and aetiology, is the reason or origination of something. The word ''etiology'' is derived from the Greek , ''aitiologia'', "giving a reason for" (, ''aitia'', "cause"; and , ''-logia''). Description In medicine, ...

(root causes), such as

hepatitis Hepatitis is inflammation of the liver tissue. Some people or animals with hepatitis have no symptoms, whereas others develop yellow discoloration of the skin and whites of the eyes ( jaundice), poor appetite, vomiting, tiredness, abdominal ...

diabetes Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ...

. Medical conditions are normally defined pathologically (i.e. based on the state of the patient), as in "liver inflammation," or clinically (i.e. based on the apparent symptoms of the patient), as in "excessive urination," and not etiologically (i.e. based on the underlying causes of the symptoms), and so it is not unusual for conditions to have multiple etiologies. Heterogeneous conditions are sometimes contrasted with homogeneous conditions, which have the same root cause for all patients in a given group. Heterogeneous conditions are often divided into

endotype 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, which is any observable characteristic or trait of a disease, such as development, biochem ...

s based on etiology.

Endotype

An endotype is a subtype of a 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 pr ...

, 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

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts * Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...

, development, biochemical or physiological properties, or behavior, 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 hea ...

s with a specific endotype present themselves within phenotypic clusters of diseases. One example is asthma, 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 language, Greek σύνδρομον, meaning "concurrence". When a sy ...

, consisting of a series of endotypes. This is related to the concept of

disease entity 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, which is any observable characteristic or trait of a disease, such as development, biochem ...

Heterogeneity in medical conditions

The term medical condition is a

nosological 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 ...

broad term that includes all diseases, disorders, injuries and

s, and it is specially suitable in the last case, in which it is not possible to speak about a single disease associated to the clinical course of the patient. While the term ''medical condition'' generally includes mental illnesses, in some contexts the term is used specifically to denote any illness, injury, or disease except for mental illnesses. The

Diagnostic and Statistical Manual of Mental Disorders The ''Diagnostic and Statistical Manual of Mental Disorders'' (DSM; latest edition: DSM-5-TR, published in March 2022) is a publication by the American Psychiatric Association (APA) for the classification of mental disorders using a common langua ...

(DSM), the widely used psychiatric manual that defines all

mental disorder A mental disorder, also referred to as a mental illness or psychiatric disorder, is a behavioral or mental pattern that causes significant distress or impairment of personal functioning. Such features may be persistent, relapsing and remitt ...

s, uses the term ''general medical condition'' to refer to all diseases, illnesses, and injuries except for

s. This usage is also commonly seen in the psychiatric literature. Some

health insurance Health insurance or medical insurance (also known as medical aid in South Africa) is a type of insurance that covers the whole or a part of the risk of a person incurring medical expenses. As with other types of insurance, risk is shared among ma ...

policies also define a ''medical condition'' as any illness, injury, or disease except for psychiatric illnesses. As it is more

value-neutral A value judgment (or value judgement) is a judgment of the rightness or wrongness of something or someone, or of the usefulness of something or someone, based on a comparison or other relativity. As a generalization, a value judgment can refer to ...

than terms like ''disease'', the term ''medical condition'' is sometimes preferred by people with health issues that they do not consider deleterious. It is also preferred when etiology is not unique, because the word disease is normally associated to the cause of the clinical problems. On the other hand, by emphasizing the medical nature of the condition, this term is sometimes rejected, such as by proponents of the autism rights movement. The term is also used in specialized areas of the medicine. A genetic or allelic heterogeneous condition is one where the same disease or condition can be caused, or contributed to, by varying different genes or alleles. In clinical trials and statistics the concepts of homogeneous and heterogeneous populations is important. The same applies for

epidemiology Epidemiology is the study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in a defined population. It is a cornerstone of public health, and shapes policy decisions and evidenc ...

References

{{reflist Diseases and disorders

Endotype

Heterogeneity in medical conditions

See also

References