A heterogeneous medical condition or heterogeneous disease is a medical term referring to a medical condition with several etiologies (root causes), such as hepatitis or diabetes. 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 endotypes based on etiology.
