Fever of Unknown Origin

Reading: pg. 413 – 420

Introduction

•      Fever:

–  Abnormal increase in body temperature

–  Continuous or intermittent

•      A fever of unknown origin (FUO) is one in which there is no known cause of the fever

–  Fever produced in response to:

•   Exogenous pyrogen (endotoxin)

•   Endogenous pyrogen (IL-1)

Mechanisms of fever (Fig. 29.1)

Causes of FUO (fig. 29.3)

Infective causes of FUO (fig. 29.4)

•             2 groups

–         Infections caused by specific pathogen

–         Infections caused by different pathogens

Treatment of FUO depends on cause

•      Diagnosis requires persistence

•      Essential to choice of appropriate treatment

•      Treatment depends on cause

FUO in specific patient groups

•             Hospital patients:

–          Operative procedures performed: transplantsà graft-vs-host disease

–          Presence of foreign bodies: intravascular devices

–          Drug therapy: drug fevers

–          Underlying disease and chemotherapy in neutropenic patients

–          Known risk factors: intravenous drug use, travel, contact with infected individuals

Infective endocarditis

•      Endogenous infection of endothelial lining of heart (may involve heart valves)

–   patients with pre-existing heart defect

•      Organisms that cause endocarditis (fig. 29.9)

•      Bacteremia can result in endocarditis

–   Most common: streptococci from oral flora

•      Patients with infective endocarditis almost always present a fever and a heart murmur.

–  Outward signs:

•   splinter hemorrhage in nailbed

•   petechial lesions in skin

•   Osler’s nodes (lesions on palm and finger tips)

•      Diagnosis:

–   Blood culture

•      Mortality rate is 20-50% even with antibiotics treatment.

•      Treatment depends on the infecting organism

–   Streptococci: penicillin, ceftriaxone or vancomycin

–   Enterococci and Methicillin-resistant staphylococci: : combinations of antibiotics are used