Pathognomonic

Pathognomonic (rare synonym pathognomic[1]) 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 derived from πάθος pathos "disease" and γνώμων gnomon "indicator" (from γιγνώσκω gignosko "I know, I recognize").

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 positive predictive value 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.

Singular pathognomonic signs are relatively uncommon. Examples of pathognomonic findings include Koplik's spots inside the mouth in measles, the palmar xanthomata seen on the hands of people suffering from hyperlipoproteinemia, Negri bodies within brain tissue infected with rabies, or a tetrad of rash, arthralgia, abdominal pain and kidney disease in a child with Henoch–Schönlein purpura.

As opposed to symptoms (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 the hypersegmented neutrophil, which is seen only in megaloblastic 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 as diabetes mellitus being defined in terms of chronic fasting blood glucose levels).

In contrast, a test with very high sensitivity 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 termed sine qua non. An example of such test is a genetic test to find an underlying mutation in certain types of hereditary colon cancer.[2][3]

Examples
DiseaseSign
Cytomegalovirus infectionOwl's eye appearance of inclusion bodies[4][5]
Hodgkin's lymphoma

Reed-Sternberg cells (giant mono- and multinucleated cells) upon microscopy

Lyme diseaseErythema chronicum migrans[6]
Inclusion body myositisFilamentous material seen in inclusion bodies under electron microscopy
HypocalcemiaTrousseau sign and Chvostek sign
Tetanus or Strychnine poisoningRisus sardonicus
MeaslesKoplik's spots
Wilson's diseaseKayser–Fleischer ring
DiphtheriaPseudomembrane on tonsils, pharynx and nasal cavity
Chronic hemorrhagic pancreatitisGrey-Turner's sign (ecchymosis in flank area)
CholeraRice-watery stool
Enteric feverRose spots in abdomen
MeningitisKernig's sign and Brudzinski's sign
Angina pectorisLevine's sign (hand clutching of chest)[7]
Patent ductus arteriosusMachine-like murmur
Parkinson's diseasePill-rolling tremors
Whipple's diseaseOculo-masticatory myorhythmia
Acute myeloid leukemiaAuer rod
Multiple sclerosisBilateral internuclear ophthalmoplegia
PericarditisPericardial friction rub
Rheumatic feverAschoff bodies
RabiesHydrophobia and negri bodies
GoutTophi
MASCETV6-NTRK3
Acute tubular necrosisMuddy brown casts
Granulosa cell tumour Call-Exner bodies
Malakoplakia Michaelis–Gutmann bodies
Narcolepsy (with cataplexy) Cataplexy
Endodermal sinus tumor Schiller–Duval body
Sickle cell disease Vaso-occlusive crises[8]

See also

References
  1. "Pathognomic". Oxford Dictionaries.
  2. 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. PMID 17999161. S2CID 20103607.
  3. 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. PMID 21044965.
  4. Page 268 in: Gibbs RD, Sweet RL (2009). Infectious Diseases of the Female Genital Tract. Hagerstwon, MD: Lippincott Williams & Wilkins. ISBN 978-0-7817-7815-2.
  5. Mattes FM, McLaughlin JE, Emery VC, Clark DA, Griffiths PD (August 2000). "Histopathological detection of owl's eye inclusions is still specific for cytomegalovirus in the era of human herpesviruses 6 and 7". Journal of Clinical Pathology. 53 (8): 612–4. doi:10.1136/jcp.53.8.612. PMC 1762915. PMID 11002765.
  6. Ogden NH, Lindsay LR, Morshed M, Sockett PN, Artsob H (January 2008). "The rising challenge of Lyme borreliosis in Canada". Canada Communicable Disease Report. 34 (1): 1–19. PMID 18290267.
  7. Swartz MH (2014). Textbook of Physical Diagnosis: History and Examination. Elsevier. p. 354. ISBN 9780323225076.
  8. Rami Helvaci M, Ayyildiz O, Gundogdu M (July 2013). "Gender differences in severity of sickle cell diseases in non-smokers". Pakistan Journal of Medical Sciences. 29 (4): 1050–4. PMC 3817781. PMID 24353686.
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