Pathognomonic

Pathognomonic (often misspelled as pathognomic and sometimes as pathomnemonic) is a term, often used in medicine, that means characteristic for a particular disease. A pathognomonic sign is a particular sign whose presence means that a particular disease is present beyond any doubt. Labelling a sign or symptom "pathognomonic" represents a marked intensification of a "diagnostic" sign or symptom.

The word is an adjective of Greek origin (παθογνωμονικόν [σύμπτωμα]), derived from páthos ("πάθος" meaning "disease") and gnōmon ("γνώμον" meaning "judge").

Practical use

While some findings may be classic, typical or highly suggestive in a certain condition, they may not occur uniquely in this condition and therefore may not directly imply a specific diagnosis. A pathognomonic sign or symptom has very high specificity but does not need to have high sensitivity: for example it can sometimes be absent in a certain disease, since the term only implies that, when it is present, the doctor instantly knows the patient's illness. The presence of a pathognomonic finding allows immediate diagnosis, since there are no other conditions in the differential diagnosis.