What is Fever? | Part 1

approach to fever intro fever also called pyrexia is one of the most common presenting complaints in medical practice it is defined as a body temperature that is above the normal range for that individual without any physiological cause to it in other words temperature raised due to exercise or menstrual cycle doesn't count as fever this is usually above 38 degrees Celsius recorded by thermometer in this case oral and rectal temperature readings are more accurate than exhilarate M the most important thing to keep in mind is that fever in it of itself is not a disease but rather a symptom that indicates an underlying disease process mechanism of fever body temperature is usually set to its normal range by the hypothalamus which acts as sort of a thermostat when the body suffers from certain pathological processes namely inflammation certain the chemicals are released by the body collectively called pyrogens in other words of which is interleukin 2 pyrogens set the thermo regulatory point of the hypothalamus to a higher temperature thus resulting in fever the causes of fever can be divided into the broad categories of one infections which is the most common cause of pyrexia it can include bacterial viral fungal or parasitic infections two clots three cancers four autoimmune diseases and five miscellaneous which can include things like heat stroke medications brain lesions and thyroid storm to name a few diagnosing the cause of fever we have mentioned five categories of diseases that usually result in fever then each category consists of a multitude of possible diseases in order to narrow down our diagnosis we need to do a thorough history and examination and request appropriate lab investigations where relevant fever is usually accompanied by other symptoms as well which may god the diagnosis of underlying disease important questions to ask in history these can be broadly divided into two categories one general fever related to review of systems fever specific questions include the duration of fever the timing of the fever what time of day is it more prominent the character is a remitting or relapsing is it accompanied by chills or rigors is their night sweating is their weight loss is their pain anywhere review of symptoms is a systemic approach to identifying accompanying symptoms in other body organs this is especially important in identifying a possible focus of infection ask relevant questions pertaining to each organ system and move from head to toe so for example ask about headache neck stiffness eye pain skin rashes or itching running ear pain or discharge coughing spud 'm sore throat pain on swallowing is there difficulty breathing or chest pain is there any abdominal pain any change in bowel habits is there any lymph node enlargement any burning sensation while urinating any discharge from genitals any recent injuries any muscle or bone pain any recent surgery your history will be directed further by the patient's responses and we'll probably start moving towards a probable diagnosis examine the relevant organ system in thorough detail you mainly need to decide which of the five categories does the disease belong to and which organ system is likely affected for example acute fever with complain of burning sensation during urination points to infection of the urinary tract whereas chronic low-grade fever with anemia and weight loss might be indicating a hematological cancer you


  1. Well, is known that the principal pyrogens are IL-1, TNFa, IL-6. But also IL-2 causes fever but by an indirect mechanism rather than by a direct effect on the hypothalamus as a true Endogenous Pyrogen.

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