Any symptom, disease or condition for which the cause can't be determined or is of unknown origin. The word comes from Greek: idios means separate and pathos means suffering.
Many allergies are idiopathic. When a patient breaks out in a rash, or hives, or any form of swelling, and the cause can't be determined, the allergy will be considered idiopathic until (or if) the cause is later determined.
A symptom, disease or condition can be idiopathic for one person, but not necessarily for another. For example, if a patient has a seizure and is known to have epilepsy, then the cause for the seizure is known. But if a patient with no known disease or condition has a seizure, it may be considered idiopathic until a diagnosis is assigned later.
