Medical term meaning "characteristic for a particular disease"
Pathognomonic (synonympathognomic[1]) is a term, often used inmedicine, that means "characteristic for a particulardisease". A pathognomonicsign is a particular sign whose presence means that a particular disease is present beyond any doubt. The absence of a pathognomonic sign does not rule out the disease. Labelling a sign orsymptom "pathognomonic" represents a marked intensification of a "diagnostic" sign or symptom.
The word is an adjective ofGreek origin derived from πάθοςpathos 'disease' and γνώμωνgnomon 'indicator' (from γιγνώσκωgignosko 'I know, I recognize').
While some findings may be classic, typical or highly suggestive in a certain condition, they may not occuruniquely in this condition and therefore may not directly imply a specific diagnosis. A pathognomonic sign or symptom has very highpositive predictive value and highspecificity but does not need to have highsensitivity: 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 thedifferential diagnosis.[citation needed]
As opposed tosymptoms (reported subjectively by the patient and not measured) and signs (observed by the physician at the bedside on physical exam, without need for a report) a larger number of medical test results are pathognomonic. An example is thehypersegmented neutrophil, which is seen only inmegaloblastic anemias (not a single disease, but a set of closely related disease states). More often a test result is "pathognomonic" only because there has been a consensus to define the disease state in terms of the test result (such asdiabetes mellitus being defined in terms of chronic fastingblood glucose levels).[citation needed]
In contrast, a test with very highsensitivity rarely misses a condition, so a negative result should be reassuring (the disease tested for is absent). A sign or symptom with very high sensitivity is often termedsine qua non. An example of such test is a genetic test to find an underlying mutation in certain types ofhereditary colon cancer.[2][3]
^Lynch HT, Lynch JF, Lynch PM, Attard T (2007). "Hereditary colorectal cancer syndromes: molecular genetics, genetic counseling, diagnosis and management".Familial Cancer.7 (1):27–39.doi:10.1007/s10689-007-9165-5.PMID17999161.S2CID20103607.
^Lynch HT, Lanspa SJ (November 2010). "Colorectal cancer survival advantage in MUTYH-associated polyposis and Lynch syndrome families".Journal of the National Cancer Institute.102 (22):1687–9.doi:10.1093/jnci/djq439.PMID21044965.
^Page 268 in:Gibbs RD, Sweet RL (2009).Infectious Diseases of the Female Genital Tract. Hagerstwon, MD: Lippincott Williams & Wilkins.ISBN978-0-7817-7815-2.
