Signs and symptoms are diagnostic indications of anillness, injury, or condition.
Signs are objective and externally observable; symptoms are a person's reported subjective experiences.[1]
A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showing on amedical scan. A symptom is something out of the ordinary that is experienced by an individual such as feeling feverish, a headache or other pains in the body,[2][3] which occur as the body's immune system fights off an infection.[4][5][6]
A medical sign is anobjective observable indication of a disease, injury, ormedical condition that may be detected during aphysical examination.[7] These signs may be visible, such as arash orbruise, or otherwise detectable such as byusing a stethoscope or takingblood pressure. Medical signs, along withsymptoms, help in forming adiagnosis. Some examples of signs arenail clubbing of either the fingernails or toenails[8] or anabnormal gait.[9]
A symptom is something felt or experienced, such as pain or dizziness. Signs and symptoms are not mutually exclusive, for example a subjective feeling of fever can be noted as sign by using a thermometer that registers a high reading.[10] TheCDC lists various diseases by their signs and symptoms such as formeasles which includes a highfever,conjunctivitis, andcough, followed a few days later by the measlesrash.[11]
Cardinal signs and symptoms are very specific even to the point of beingpathognomonic. A cardinal sign or cardinal symptom can also refer to the major sign or symptom of a disease.[12] Abnormalreflexes can indicate problems with thenervous system. Signs and symptoms are also applied to physiological states outside the context of disease, as for example when referring to thesigns and symptoms of pregnancy, or the symptoms ofdehydration. Sometimes a disease may be present without showing any signs or symptoms when it is known as beingasymptomatic.[13] The disorder may be discovered through tests including scans. Aninfection may be asymptomatic but still betransmissible.[13]
Signs and symptoms are often non-specific, but some combinations can be suggestive of certaindiagnoses, helping to narrow down what may be wrong. A particular set of characteristic signs and symptoms that may be associated with a disorder is known as asyndrome.
When a disease is evidenced by symptoms it is known assymptomatic. There are many conditions includingsubclinical infections that display no symptoms, and these are termedasymptomatic.
Signs and symptoms may be mild or severe, brief or longer-lasting when they may become reduced (remission), or then recur (relapse orrecrudescence) known as aflare-up. A flare-up may show more severe symptoms.[14]
The termchief complaint, also "presenting problem", is used to describe the initial concern of an individual when seeking medical help, and once this is clearly noted ahistory of the present illness may be taken. The symptom that ultimately leads to adiagnosis is called a cardinal symptom.[citation needed] Some symptoms can be misleading as a result ofreferred pain, where for example a pain in the right shoulder may be due toan inflamed gallbladder and not to presumed muscle strain.[15]
Many diseases have an earlyprodromal stage where a few signs and symptoms may suggest the presence of a disorder before further specific symptoms may emerge.Measles for example has a prodromal presentation that includes a hacking cough, fever, andKoplik's spots in the mouth.[16] Over half ofmigraine episodes have a prodromal phase.[17]Schizophrenia has a notable prodromal stage,[18] as hasdementia.[19]
Some symptoms arespecific, that is, they are associated with a single, specific medical condition.[citation needed]
Nonspecific symptoms, sometimes also calledequivocal symptoms,[20] are not specific to a particular condition. They include unexplained weight loss, headache, pain, fatigue, loss of appetite, night sweats, andmalaise.[21] A group of three particular nonspecific symptoms – fever, night sweats, and weight loss – over a period of six months are termedB symptoms associated withlymphoma and indicate a poor prognosis.[22]
Other sub-types of symptoms include:
Vital signs are the four signs that can give an immediate measurement of the body's overall functioning and health status. They aretemperature,heart rate,breathing rate, andblood pressure. Theranges of these measurements vary with age, weight, gender and with general health.[29]
A digital application has been developed for use in clinical settings that measures three of the vital signs (not temperature) using just asmartphone, and has been approved byNHS England. The application is registered asLifelight First, andLifelight Home is under development (2020) for monitoring-use by people at home using just the camera on their smartphone or tablet. This will additionally measureoxygen saturation andatrial fibrillation. Other devices are then not needed.[30]
Many conditions are indicated by a group of known signs, or signs and symptoms. These can be a group of three known as a triad; a group of four ("tetrad"); or a group of five ("pentad").[citation needed]
An example of a triad isMeltzer's triad presentingpurpura a rash,arthralgia painful joints, andmyalgia painful and weak muscles. Meltzer's triad indicates the conditioncryoglobulinemia.Huntington's disease is aneurodegenerative disease that is characterized by a triad of motor, cognitive, and psychiatric signs and symptoms.[31] A large number of these groups that can be characteristic of a particular disease are known as asyndrome.Noonan syndrome for example, has a diagnostic set of unique facial and musculoskeletal features.[32] Some syndromes such asnephrotic syndrome may have a number of underlying causes that are all related to diseases that affect thekidneys.[33]
Sometimes a child or young adult may have symptoms suggestive of agenetic disorder that cannot beidentified even aftergenetic testing. In such cases the termSWAN (syndrome without a name) may be used. Often a diagnosis may be made at some future point when other more specific symptoms emerge but many cases may remain undiagnosed. The inability to diagnose may be due to a unique combination of symptoms or an overlap of conditions, or to the symptoms being atypical of a known disorder, or to the disorder being extremely rare.[34]
It is possible that a person with a particular syndrome might not display every single one of the signs and/or symptoms that compose/define a syndrome.[citation needed]
Sensory symptoms can also be described aspositive symptoms, or asnegative symptoms depending on whether the symptom is abnormally present such as tingling or itchiness, or abnormally absent such asloss of smell. The following terms are used for negative symptoms –hypoesthesia is a partial loss of sensitivity to moderate stimuli, such as pressure, touch, warmth, cold.Anesthesia is the complete loss of sensitivity to stronger stimuli, such as pinprick.Hypoalgesia (analgesia) is loss of sensation to painful stimuli.[35]
Symptoms are also grouped in to negative and positive for somemental disorders such asschizophrenia.[36]Positive symptoms are those that are present in the disorder and are not normally experienced by most individuals and reflects an excess or distortion of normal functions;[37] examples arehallucinations,delusions, and bizarre behavior.[citation needed]Negative symptoms are functions that are normally found but that are diminished or absent, such asapathy andanhedonia.[37]
Dynamic symptoms are capable of change depending on circumstance, whereas static symptoms are fixed or unchanging regardless of circumstance. For example, the symptoms ofexercise intolerance are dynamic as they are brought on by exercise, but alleviate during rest. Fixedmuscle weakness is a static symptom as the muscle will be weak regardless of exercise or rest.[citation needed]
A majority of patients withmetabolic myopathies have dynamic rather than static findings, typically experiencing exercise intolerance, muscle pain, and cramps with exercise rather than fixed weakness.[38] Those with the metabolic myopathy ofMcArdle's disease (GSD-V) and some individuals withphosphoglucomutase deficiency (CDG1T/GSD-XIV), initially experience exercise intolerance during mild-moderate aerobic exercise, but the symptoms alleviate after 6–10 minutes in what is known as "second wind".
Neuropsychiatric symptoms are present in manydegenerative disorders includingdementia, andParkinson's disease. Symptoms commonly includeapathy,anxiety, anddepression.[39]Neurological and psychiatric symptoms are also present in somegenetic disorders such asWilson's disease.[40] Symptoms ofexecutive dysfunction are often found in many disorders includingschizophrenia, andADHD.[41][42]
Radiologic signs are abnormalmedical findings onimaging scanning. These include theMickey Mouse sign and theGolden S sign. When using imaging to find the cause of a complaint, another unrelated finding may be found known as anincidental finding.[43]
Cardinal signs and symptoms are those that may be diagnostic, andpathognomonic – of a certainty of diagnosis.Inflammation for example has a recognised group of cardinal signs and symptoms,[44] as doesexacerbations of chronic bronchitis,[45] andParkinson's disease.
In contrast to a pathognomonic cardinal sign, the absence of a sign or symptom can often rule out a condition. This is known by the Latin termsine qua non. For example, the absence of known genetic mutationsspecific for ahereditary disease would rule out that disease.[46] Another example is where thevaginal pH is less than 4.5, a diagnosis ofbacterial vaginosis would be excluded.[47]
Areflex is an automatic response in the body to a stimulus.[48] Its absence, reduced (hypoactive), or exaggerated (hyperactive) response can be a sign of damage to thecentral nervous system orperipheral nervous system. In thepatellar reflex (knee-jerk) for example, its reduction or absence is known asWestphal's sign and may indicate damage tolower motor neurons. When the response is exaggerated damage to theupper motor neurons may be indicated.[citation needed]
A number ofmedical conditions are associated with a distinctive facial expression or appearance known as afacies.[49] An example iselfin facies which has facial features like those of theelf, and this may be associated withWilliams syndrome, orDonohue syndrome. The most well-known facies is probably theHippocratic facies that is seen on a person as they near death.[50]
Anamnestic signs (fromanamnēstikós, ἀναμνηστικός, "able to recall to mind") are signs that indicate a past condition, for example paralysis in an arm may indicate a paststroke.[51]: 81
Some diseases includingcancers, and infections may be present but show no signs or symptomsand these are known asasymptomatic.[13] A gallstone may be asymptomatic and only discovered as anincidental finding.[13] Easily spreadable viral infections such asCOVID-19 may be asymptomatic but may still betransmissible.[52]
A symptom (fromGreek σύμπτωμα, "accident, misfortune, that which befalls",[53] from συμπίπτω, "I befall", from συν- "together, with" and πίπτω, "I fall") is a departure from normal function or feeling. Symptomatology (also called semiology) is a branch ofmedicine dealing with the signs and symptoms of a disease.[54][55][56] This study also includes theindications of adisease.[57] It was first described assemiotics byHenry Stubbe in 1670 a term now used for the study ofsign communication.[citation needed]
Prior to the nineteenth century there was little difference in the powers of observation between physician and patient. Most medical practice was conducted as a co-operative interaction between the physician and patient; this was gradually replaced by a "monolithic consensus of opinion imposed from within the community of medical investigators".[58][59] Whilst each noticed much the same things, the physician had a more informed interpretation of those things: "the physicians knew what the findings meant and the layman did not".[51]: 82
A number of advances introduced mostly in the 19th century, allowed for more objective assessment by the physician in search of a diagnosis, and less need of input from the patient.[58][59][60] During the 20th century the introduction of a wide range ofimaging techniques and other testing methods such asgenetic testing,clinical chemistry tests,molecular diagnostics andpathogenomics have made a huge impact on diagnostic capability.[61]
The recognition of signs, and noting of symptoms may lead to a diagnosis. Otherwise aphysical examination may be carried out, and amedical history taken. Furtherdiagnostic medical tests such asblood tests,scans, andbiopsies, may be needed. AnX-ray for example would soon be diagnostic of a suspectedbone fracture. A noted significance detected during an examination or from a medical test may be known as amedical finding.[65]
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