Fever is the second most common symptom caused by the hypothalamus raising the body's thermoregulatory set point through cytokines like interleukin-1, tumor necrosis factor, and interferon in response to infection or inflammation. There are different types of fever defined by temperature patterns. Fever can be caused by infections, inflammatory conditions, cancers, drugs, or unknown origins in the case of pyrexia of unknown origin. Evaluation involves taking a thorough history and physical exam to determine the cause and guide treatment of the underlying condition and fever.

1. Fever
2nd
commonest symptom
Thermostat- hypothalamus
Part of immune response

2. Definition
 Normal body temperature- 98-100° F
 Core/rectal > oral > axillary by 1° F
 Fever- regulated rise to a new thermoregulatory set-
point mediated by cytokines- IL-1, TNF, IL-6, IFN
 Hyperthermia- an increase in body temperature
over the thermoregulatory set-point, due to excessive
heat production &/or inadequate thermoregulation

3. Types
 Continuous- above normal throughout the day, with
fluctuation <1° F; e.g. viral fever
 Remittent- above normal throughout the day, with
fluctuation >1° F; e.g. IE
 Intermittent- touches normal during the day; e.g.
abscess, bacteremia, malaria
 Relapsing- short febrile episodes between day(s) of
normal temperature; e.g. malaria, typhoid
 Pel-Ebstein- relapsing fever with bouts of fever
lasting 3-10 days; e.g. Hodgkin’s

4. Causes
 Infection
 Inflammation- MI, PE, pancreatitis, polytrauma,
postoperative
 Connective tissue diseases- SLE, GCA,
rheumatic fever, Wegener’s, PAN, sarcoidosis
 Cancer- HCC/liver mets, RCC, lymphoma/leukemia,
atrial myxoma
 CNS- trauma or SOL
 Drugs

5. Pointers for infectious etiology
 Abrupt onset
 High fever +/- chills
 Systemic symptoms- malaise, myalgia
 Specific symptoms- productive cough,
dysentery, dysuria
 Tender LNE

6. Acute fever in OPD
 Viral- continuous fever, chills uncommon,
non-specific systemic symptoms
 Bacterial- intermittent fever, chills +, specific
systemic symptoms
 Malaria- relapsing fever, with chills/rigors,
non-specific systemic symptoms

7. Evaluation
History
&
Physical examination

8. Treatment
Treat fever- paracetamol, cold
sponging
&
Treat etiology/cause

9. PUO/FUO
Pyrexia/Fever of unknown origin

10. Definition- Classic FUO
 Fever >101° F on >1 occasion
 Undiagnosed despite
 3 outpatient visits
 3 days in hospital
 1 week of intelligent & invasive
ambulatory investigation

11. Definition- contd.
 Nosocomial FUO- undiagnosed fever in
patients admitted for at least 24 hours
 Neutropenic FUO- undiagnosed fever in
patient with ANC <500/uL
 HIV associated FUO

12. Important causes
 Tuberculosis
 Lymphoma
 Sarcoidosis
 Pulmonary embolism
 Infective endocarditis
 Abscess
 Drug-induced

13. Work-up
 History
 Physical examination
 CBC, LFT, TFT, urinalysis
 Blood cultures
 CxR
 Ultrasound abdomen
 CT scan- chest & abdomen
 Echocardiography
 Gallium-67 scan
 PET scan with radiolabelled FDG
 Bone marrow aspiration &/or biopsy
 Other serological tests- ANA, ADA, ACE etc.

14. Treatment
Wait till diagnosis, except
Urgent empirical antibiotics in
neutropenic fever