Fever and pyrexia of unknown origin Flashcards
Where is body temp controlled
Sensors and receptors in hypothalamus
Temp reducing responses
Vasodilation
Sweating
Increased ventilation
Temp raisinging repsonses (mechainisms of effervescence)
Vasoconstriction
Shivering
Piloerection
Increased metabolism
Hyperthemia vs fever
Bodies mechanisms to cool not sufficient enugh to cool body temperature, so whole body temp rises = hyperthermia
Fever = prostaglandin E1 acts on thermostatic set point regardless of external environemnt
eg hyperhtermia = external conditions, fever = internal.
Why do we ger fever
Make ourselves hotter - not ideal for bacteria but ideal for immune system functioning
Pyrogenic factors - infectious
microbes and microbial prodcts eg
Gram - bacteria - LPS/Endotoxin
G+ - exotoxins, peptioglycans
Viruses
Other microorganisms
Non infectious pyrogenic factors
antigen-antibody complexes
Compleetn
Non infectious inflammation - genesis irritatnts
Drugs - antibiotics, steroids, chemotheray agents
Cytokines that are pyrogenic (fever inducing)
TNF
IL-1, 6
IFN
Where are endogenous pyrogens derived from
Cells in boody - cytokines released by
Mononuclear, macrophages, T-lymphocytes, kupffer cells, endothelial cells, tumour cells
Classical fever patterns
Sustained - constant above basal temp, half degree variation
Intermittent - temp returns to normal, swings of fever in cycles less than 24 hours
Remittent - significant rapid variation, baseline does not return to normal (rises)
Relapsing - period of any pattern fever -> afebrile -> returning fever >24 hr cycle
What is intermittent fever classically ass with
Abscesses eg empyemas
What causing relapsing fever
Malaria etc
48-72 hr cycles of fever relapsing
What is defined as pyrexia of unknown origin
Sustained or recurrent pyrexias >3 weeks
No identified cause after evaluation in hospital for 3 dyas or >3 outpatient visits
Types of pyrexia of unknown origin
Classic
Nosocomial
Immunodeficient
HIV
Common causes of classic fever of unexplained origin
1/4 - undiagnosed
20% - miscellaneous
20% - Connective tissue disorders
1/4 - infection
15% - neoplasms eg malignant
What happens to causes of FUO >60 yrs
Causes are different -Infections <10%
CTD >30%
Malignancy much more important
Infectious causes of FUO
Abscess
Infective endocarditis
TB
Complicated UTI
Travel - melioidosis, visceral leishmaniasis, amoebic abcess
Connective tissue auses of FUO in young
Stills disease
JRA
Adult CTD causes of FUO
RA
SLE
Elderly CTD causes of FUO
Giant cell arteritis
Polymyalgia Rheumatica
When is an FUO nosocomial
> 48 hrs hospitalised
No infection present or incubating at admission
Diagnosis uncertain >3 days appropriate evaluation
Microbiologucal cultures incubated for >2 days
Causes of nosocomial FUO
Catheters/devices
Thrombophlebitis
UTI/RTI
Drug fevers
C.diff treatment (broad spec ABs)
ICU - ventialtors, ET tubes, NG tubes
Stroke
FUO imunodeficiency causes
Cell-mediated imunodeficiency - congenital, biologic/immunomodulatory therapies
Neutropenia - haematological, chemotherapy
Definition of neutropenia
<500 neurtophils/ul
What need to be careful with FUO in imunodeficiency
Blunted typical inflam response eg lacking symtpoms, ‘normal’ WCC when been low
Lack of radiological changes
FUO in HIV
Seroconversion illness
AIDS -
PCP, Mycobacterial, toxoplasmosis, CMV, lymphoma
Erythema nodosum ass
TB, strep, IBD, Recent anti-inflam drugs
Infective endo signs
Janeway lesions, oslers nodes, splinter haemorrhages, petechiae eye
Lab investigations for PUO
Blood cultures
Blood borne viruses - HIV.HBV/HCV
Blood films - cells, parasites
Serology
FBC
U+E/LFT/Bone chemistry
TFTs
Inflam markers - CRP, ESR, ALP
Autoantibodies - ANA, dsDNA
Stool, urine samples
Ascitic/pleural/synovial fluid
Bone marrow
Biopsy
Imaging for FUO
CXR
US liver/spleen
Cross section CT
HRCT
CT PET
Labelled white cell scan/scintigraphy (cancer monitoring)
Bone scan
MRI
