Pathognomonic is a term, often used in medicine

Medicine

Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....

, that means characteristic for a particular disease

Disease

A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...

. A pathognomonic sign

Medical sign

A medical sign is an objective indication of some medical fact or characteristic that may be detected by a physician during a physical examination of a patient....

 is a particular sign whose presence means that a particular disease is present beyond any doubt. Labelling a sign or symptom

Symptom

A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...

 "pathognomonic" represents a marked intensification of a "diagnostic" sign or symptom.

The word is an adjective of Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 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

Sensitivity and specificity

Sensitivity and specificity are statistical measures of the performance of a binary classification test, also known in statistics as classification function. Sensitivity measures the proportion of actual positives which are correctly identified as such Sensitivity and specificity are statistical...

 but does not need to have high sensitivity

Sensitivity and specificity

Sensitivity and specificity are statistical measures of the performance of a binary classification test, also known in statistics as classification function. Sensitivity measures the proportion of actual positives which are correctly identified as such Sensitivity and specificity are statistical...

: 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, on the other hand, allows immediate diagnosis, since there are no other conditions in the differential diagnosis

Differential diagnosis

A differential diagnosis is a systematic diagnostic method used to identify the presence of an entity where multiple alternatives are possible , and may also refer to any of the included candidate alternatives A differential diagnosis (sometimes abbreviated DDx, ddx, DD, D/Dx, or ΔΔ) is a...

.

Singular pathognomonic signs are relatively uncommon. Examples of pathognomonic findings include Koplik's spots

Koplik's spots

Koplik spots are a prodromic viral enanthem of measles manifesting two days before the measles rash itself. They are characterized as clustered, white lesions on the buccal mucosa near each Stenson's duct and are pathognomonic for measles...

 inside the mouth

Mouth

The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....

 in measles

Measles

Measles, also known as rubeola or morbilli, is an infection of the respiratory system caused by a virus, specifically a paramyxovirus of the genus Morbillivirus. Morbilliviruses, like other paramyxoviruses, are enveloped, single-stranded, negative-sense RNA viruses...

, the palmar xanthoma

Xanthoma

A xanthoma , from Greek xanthos, ξανθος, "yellow", is a deposition of yellowish cholesterol-rich material in tendons or other body parts in various disease states...

ta seen on the hands of people suffering from hyperlipoproteinemia, or a tetrad of rash

Rash

A rash is a change of the skin which affects its color, appearance or texture. A rash may be localized in one part of the body, or affect all the skin. Rashes may cause the skin to change color, itch, become warm, bumpy, chapped, dry, cracked or blistered, swell and may be painful. The causes, and...

, arthralgia

Arthralgia

Arthralgia literally means joint pain; it is a symptom of injury, infection, illnesses or an allergic reaction to medication....

, abdominal pain

Abdominal pain

Abdominal pain can be one of the symptoms associated with transient disorders or serious disease. Making a definitive diagnosis of the cause of abdominal pain can be difficult, because many diseases can result in this symptom. Abdominal pain is a common problem...

 and kidney

Kidney

The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...

 disease in a child with Henoch-Schönlein purpura

Henoch-Schönlein purpura

Henoch–Schönlein purpura is a disease of the skin and other organs that most commonly affects children. In the skin, the disease causes palpable purpura ; often with joint and abdominal pain...

.

As opposed to symptom

Symptom

A symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...

s (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. A example is the hypersegmented neutrophil

Hypersegmented neutrophil

A hypersegmented neutrophil is a clinical laboratory finding. It is visualized by drawing blood from a patient and viewing the blood smeared on a slide under a microscope. Normally, the number of segments in the nucleus of a neutrophil increases as it matures and ages, after being released into the...

, which is seen only in megaloblastic anemia

Megaloblastic anemia

Megaloblastic anemia is an anemia that results from inhibition of DNA synthesis in red blood cell production. When DNA synthesis is impaired, the cell cycle cannot progress from the G2 growth stage to the mitosis stage...

s (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

Diabetes mellitus

Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...

 being defined in terms of chronic fasting blood glucose levels).

In contrast, a test with very high sensitivity

Sensitivity and specificity

Sensitivity and specificity are statistical measures of the performance of a binary classification test, also known in statistics as classification function. Sensitivity measures the proportion of actual positives which are correctly identified as such Sensitivity and specificity are statistical...

 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

Sine qua non

Sine qua non or condicio sine qua non refers to an indispensable and essential action, condition, or ingredient...

. An example of such test is a genetic test to find an underlying mutation in certain types of hereditary colon cancer.

Examples

Very few of the examples here are pathognomonic in the true sense of the word. For example, Parkinsonism is not only seen in Parkinson's disease.

Disease	Sign
Cytomegalovirus infection	Owl's eye appearance of inclusion bodies Inclusion bodies Inclusion bodies are nuclear or cytoplasmic aggregates of stainable substances, usually proteins. They typically represent sites of viral multiplication in a bacterium or a eukaryotic cell and usually consist of viral capsid proteins...
Lyme Disease Lyme disease Lyme disease, or Lyme borreliosis, is an emerging infectious disease caused by at least three species of bacteria belonging to the genus Borrelia. Borrelia burgdorferi sensu stricto is the main cause of Lyme disease in the United States, whereas Borrelia afzelii and Borrelia garinii cause most...	Erythema chronicum migrans Erythema chronicum migrans Erythema chronicum migrans refers to the rash often seen in the early stage of Lyme disease. It can appear anywhere from one day to one month after a tick bite. This rash does not represent an allergic reaction to the bite, but rather an actual skin infection with the Lyme bacteria, Borrelia...
Inclusion body myositis Inclusion body myositis Inclusion body myositis is an inflammatory muscle disease, characterized by slowly progressive weakness and wasting of both distal and proximal muscles, most apparent in the muscles of the arms and legs...	Filamentous material seen in inclusion bodies under electron microscopy
Hypocalcemia	Trousseau sign Trousseau sign of latent tetany Trousseau sign of latent tetany is a medical sign observed in patients with low calcium. This sign may become positive before other gross manifestations of hypocalcemia such as hyperreflexia and tetany, but is generally believed to be more sensitive than the Chvostek sign for hypocalcemia.To...  and Chvostek sign Chvostek sign The Chvostek sign is one of the signs of tetany seen in hypocalcemia. It refers to an abnormal reaction to the stimulation of the facial nerve. When the facial nerve is tapped at the angle of the jaw , the facial muscles on the same side of the face will contract momentarily because of...
Tetanus Tetanus Tetanus is a medical condition characterized by a prolonged contraction of skeletal muscle fibers. The primary symptoms are caused by tetanospasmin, a neurotoxin produced by the Gram-positive, rod-shaped, obligate anaerobic bacterium Clostridium tetani...	Risus sardonicus Risus sardonicus Risus sardonicus is a highly characteristic, abnormal, sustained spasm of the facial muscles that appears to produce grinning.The name of the condition derives from the appearance of raised eyebrows and an open "grin" - which can appear malevolent to the lay observer - displayed by those suffering...
Bulimia Nervosa Bulimia nervosa Bulimia nervosa is an eating disorder characterized by binge eating and purging or consuming a large amount of food in a short amount of time, followed by an attempt to rid oneself of the food consumed, usually by purging and/or by laxative, diuretics or excessive exercise. Bulimia nervosa is...	Chipmunk facies (parotid gland swelling) (Chipmunk facies also seen in marrow expansion secondary to Beta Thalassemia Thalassemia Thalassemia is an inherited autosomal recessive blood disease that originated in the Mediterranean region. In thalassemia the genetic defect, which could be either mutation or deletion, results in reduced rate of synthesis or no synthesis of one of the globin chains that make up hemoglobin...  Major)
Leprosy Leprosy Leprosy or Hansen's disease is a chronic disease caused by the bacteria Mycobacterium leprae and Mycobacterium lepromatosis. Named after physician Gerhard Armauer Hansen, leprosy is primarily a granulomatous disease of the peripheral nerves and mucosa of the upper respiratory tract; skin lesions...	Leonine facies Leonine facies Leonine facies: a face that resembles that of a lion. It is seen in multiple conditions and has been classically described for Lepromatous leprosy as well as Paget's disease of bone...  (thickened lion-like facial skin)
Measles Measles Measles, also known as rubeola or morbilli, is an infection of the respiratory system caused by a virus, specifically a paramyxovirus of the genus Morbillivirus. Morbilliviruses, like other paramyxoviruses, are enveloped, single-stranded, negative-sense RNA viruses...	Koplik's spots Koplik's spots Koplik spots are a prodromic viral enanthem of measles manifesting two days before the measles rash itself. They are characterized as clustered, white lesions on the buccal mucosa near each Stenson's duct and are pathognomonic for measles...
Diphtheria Diphtheria Diphtheria is an upper respiratory tract illness caused by Corynebacterium diphtheriae, a facultative anaerobic, Gram-positive bacterium. It is characterized by sore throat, low fever, and an adherent membrane on the tonsils, pharynx, and/or nasal cavity...	Pseudomembrane on tonsils, pharynx and nasal cavity
Chronic hemorrhagic pancreatitis Chronic pancreatitis Chronic pancreatitis is a long-standing inflammation of the pancreas that alters its normal structure and functions. It can present as episodes of acute inflammation in a previously injured pancreas, or as chronic damage with persistent pain or malabsorption....	Grey-Turner's sign Grey-Turner's sign Grey Turner's sign refers to bruising of the flanks.This sign takes 24–48 hours. It can predict a severe attack of acute pancreatitis, with mortality rising from 8-10% to 40%.It is a sign of retroperitoneal hemorrhage....  (ecchymosis in flank area)
Cholera Cholera Cholera is an infection of the small intestine that is caused by the bacterium Vibrio cholerae. The main symptoms are profuse watery diarrhea and vomiting. Transmission occurs primarily by drinking or eating water or food that has been contaminated by the diarrhea of an infected person or the feces...	Rice-watery stool Infectious diarrhea Infectious diarrhea or Contagious diarrhea may be defined as diarrhea caused by an infection of the digestive system by a bacterium, virus, or parasite that results in frequent bowel motions producing excessive amounts of liquidy feces.-Causes:...
Enteric fever	Rose spots Rose spots Rose spots are red macular lesions 2-4 millimeters in diameter occurring in patients suffering from enteric fever . These fevers occur following infection by Salmonella typhi and Salmonella paratyphi respectively...  in abdomen
Meningitis Meningitis Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...	Kernig's sign and Brudzinski's sign
Cholecystitis Cholecystitis -Signs and symptoms:Cholecystitis usually presents as a pain in the right upper quadrant. This is known as biliary colic. This is initially intermittent, but later usually presents as a constant, severe pain. During the initial stages, the pain may be felt in an area totally separate from the site...	Murphy's sign Murphy's sign In medicine, Murphy's sign refers to a maneuver during a physical examination as part of the abdominal examination and a finding elicited in ultrasonography. It is useful for differentiating pain in the right upper quadrant...  (pain on deep inspiration when inflamed gallbladder is palpated)
Angina pectoris	Levine's sign Levine's sign Levine's sign is a clenched fist held over the chest to describe ischemic chest pain. As the referred pain associated with ischemia radiates to the area of the left proximal forelimb, the right, unaffected arm is used to produce the gesture....  (hand clutching of chest)
Patent ductus arteriosus Patent ductus arteriosus Patent ductus arteriosus is a congenital disorder in the heart wherein a neonate's ductus arteriosus fails to close after birth. Early symptoms are uncommon, but in the first year of life include increased work of breathing and poor weight gain...	Machine-like murmur
Pleural Effusion Pleural effusion Pleural effusion is excess fluid that accumulates between the two pleural layers, the fluid-filled space that surrounds the lungs. Excessive amounts of such fluid can impair breathing by limiting the expansion of the lungs during ventilation.-Pathophysiology:...	Stony-dull percussion
Parkinson's disease Parkinson's disease Parkinson's disease is a degenerative disorder of the central nervous system...	Pill-rolling tremors Parkinsonism Parkinsonism is a neurological syndrome characterized by tremor, hypokinesia, rigidity, and postural instability. The underlying causes of parkinsonism are numerous, and diagnosis can be complex...
Whipple's disease Whipple's disease Whipple's disease is a rare, systemic infectious disease caused by the bacterium Tropheryma whipplei. First described by George Hoyt Whipple in 1907 and commonly considered a gastrointestinal disorder, Whipple's disease primarily causes malabsorption but may affect any part of the body including...	Oculo-Masticatory Myorhythmia
Acute Myeloid Leukemia Acute myeloid leukemia Acute myeloid leukemia , also known as acute myelogenous leukemia, is a cancer of the myeloid line of blood cells, characterized by the rapid growth of abnormal white blood cells that accumulate in the bone marrow and interfere with the production of normal blood cells. AML is the most common acute...	Auer rod
Multiple Sclerosis Multiple sclerosis Multiple sclerosis is an inflammatory disease in which the fatty myelin sheaths around the axons of the brain and spinal cord are damaged, leading to demyelination and scarring as well as a broad spectrum of signs and symptoms...	Bilateral internuclear ophthalmoplegia Internuclear ophthalmoplegia Internuclear ophthalmoplegia is a disorder of conjugate lateral gaze in which the affected eye shows impairment of adduction. When an attempt is made to gaze contralaterally , the affected eye adducts minimally, if at all. The contralateral eye abducts, however with nystagmus...
Congestive heart failure Congestive heart failure Heart failure often called congestive heart failure is generally defined as the inability of the heart to supply sufficient blood flow to meet the needs of the body. Heart failure can cause a number of symptoms including shortness of breath, leg swelling, and exercise intolerance. The condition...	Third heart sound Third heart sound The third heart sound or S3 is a rare extra heart sound that occurs soon after the normal two "lub-dub" heart sounds .-Physiology:It occurs at the beginning of diastole approximately 0.12 to 0.18 seconds after S2...
Pericarditis Pericarditis Pericarditis is an inflammation of the pericardium . A characteristic chest pain is often present.The causes of pericarditis are varied, including viral infections of the pericardium, idiopathic causes, uremic pericarditis, bacterial infections of the precardium Pericarditis is an inflammation of...	Pericardial friction rub Pericardial friction rub A pericardial friction rub, also pericardial rub, is an audible medical sign used in the diagnosis of pericarditis. Upon auscultation, this sign is an extra heart sound of to-and-fro character, typically with three components, two systolic and one diastolic. It resembles the sound of squeaky...
Neurofibromatosis Neurofibromatosis Neurofibromatosis is a genetically-inherited disorder in which the nerve tissue grows tumors that may be benign or may cause serious damage by compressing nerves and other tissues...  I	Plexiform neurofibroma
Hodgkin's lymphoma Hodgkin's lymphoma Hodgkin's lymphoma, previously known as Hodgkin's disease, is a type of lymphoma, which is a cancer originating from white blood cells called lymphocytes...	Pain within minutes after drinking alcohol. Reed-Sternberg cells (giant mono- and multinucleated cells).
Pyelonephritis Pyelonephritis Pyelonephritis is an ascending urinary tract infection that has reached the pyelum or pelvis of the kidney. It is a form of nephritis that is also referred to as pyelitis...	White blood cell casts
Rheumatic fever Rheumatic fever Rheumatic fever is an inflammatory disease that occurs following a Streptococcus pyogenes infection, such as strep throat or scarlet fever. Believed to be caused by antibody cross-reactivity that can involve the heart, joints, skin, and brain, the illness typically develops two to three weeks after...	Aschoff nodules
Rabies Rabies Rabies is a viral disease that causes acute encephalitis in warm-blooded animals. It is zoonotic , most commonly by a bite from an infected animal. For a human, rabies is almost invariably fatal if post-exposure prophylaxis is not administered prior to the onset of severe symptoms...	Hydrophobia Hydrophobia Hydrophobia or hydrophobe may refer to:* Rabies, especially a set of symptoms of the later stages of an infection, in which the victim has difficulty swallowing, shows panic when presented with liquids to drink, and cannot quench his or her thirst....  and Negri bodies Negri bodies Negri bodies are eosinophilic, sharply outlined, pathognomonic inclusion bodies found in the cytoplasm of certain nerve cells containing the virus of rabies, especially in Ammon's horn of the hippocampus. Often also found in the cerebellar cortex of postmortem brain samples of rabies victims.They...