Heterogeneous medical condition in medicine are those medical conditions which have several etiologies, like hepatitis or diabetes. Medical conditions are normally defined pathologically (liver inflammation) or clinically (excessive urination) and not etiologically, and therefore it is normal to have more than one cause for them. The word is used as an opposition to homogeneous, meaning that given a group of patients, the disease is the same for all of them.
When a condition is heterogeneous, it is normally divided in endotypes.
An endotype is a subtype of a 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 morphology, development, biochemical or physiological properties, or behavior, without any implication of a mechanism. It is envisaged that patients with a specific endotype present themselves within phenotypic clusters of diseases.
One example is asthma, which is considered to be a syndrome, consisting of a series of endotypes. This is related to the concept of disease entity
The term medical condition is a nosological broad term that includes all diseases, disorders, injuries and syndromes, 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 (DSM), the widely used psychiatric manual that defines all mental disorders, uses the term general medical condition to refer to all diseases, illnesses, and injuries except for mental disorders. This usage is also commonly seen in the psychiatric literature. Some health insurance policies also define a medical condition as any illness, injury, or disease except for psychiatric illnesses.