Hyperpyrexia

In medicine, hyperpyrexia is an excessive and unusual elevation of set body temperature greater than or equal to 41.1° Celsius (106°F), or extremely high fever. Such a high temperature is considered a medical emergency. It differs from hyperthermia in that in hyperthermia the body temperature is too high above the set point, whereas in hyperpyrexia the body's temperature regulation mechanism sets the normal body temperature too high. It is very often fatal.

Causes
Some of the more common causes of hyperpyrexia include:


 * Excessive exposure to heat or the sun (also called heat hyperpyrexia, a part of heatstroke), especially if intense exercise is done during such exposure
 * amphetamine or other stimulant abuse, which can aggravate the effects of heat hyperpyrexia, or which can cause it by itself, such as the drug PMA which was the cause of a 115F (46.1 C) fever
 * idiosyncratic drug reactions
 * withdrawal from barbiturates, alcohol, or other anxiolytics, although it is less common with benzodiazepines
 * serotonin syndrome, caused by combining two or more different serotonin agonists, such as antidepressants, stimulants (prescribed or street drugs), migraine medications, or common cold medicines (including decongestants, antihistamines, and dextromethorphan)
 * septicemia (a generalized bacterial infection of the blood)
 * some viral infections, such as mononucleosis
 * a thyrotoxic crisis (in hyperthyroidism)
 * Malignant hyperthermia is a particular condition accompanied by the breakdown of muscle following its over-excitation, in response to certain anesthetics in humans, and other stimuli in animals, such as pigs
 * Intense and prolonged convulsions
 * Neuroleptic malignant syndrome (NMS) can also cause hyperpyrexia after the administration of antipsychotic drugs.