Infectious Disease Compendium

Faget Sign

Diagnosis

Aka pulse-temperature disassociation (it is French, so pronounced fah-jay. Warning: using a hard g will result in suffering the approbation of others).

Liebermeister's rule: When the temperature goes up a degree, the pulse should go up 10 (except, of course, when the patient has heart block from their myocardial abscess or is on beta blockers). So when the febrile patients does not get appropriately tachycardic, they have Faget sign.

It has interesting differential that is always fun for Chief of Service rounds: typhoid fever, brucellosis, psittacosis, legionellosis, tularemia, yellow fever (for which it was first observed), dengue are the big ones. Also Colorado tick fever, Mycoplasma pneumonia.

Last Update: 07/10/18.