Fever of Unknown Origin

DESCRIPTION

Fever of unknown origin (FUO) implies

• A febrile illness (38.3°C on multiple occasions)
• Present for >14 days
• No apparent source despite careful history taking, physical exam, and preliminary lab studies

ETIOLOGY

• Etiology has changed as the use of more sensitive tests (e.g., MRI, polymerase chain reaction [PCR] tests) permits earlier detection of many conditions that caused FUO in the past.
• Fever resolves in 40–60% of children without identification of a specific cause.
• FUO in the pediatric population is more often an unusual presentation of a common disease than a common presentation of an unusual disease.
• Common infectious causes
  • Respiratory infections (otitis media, mastoiditis, sinusitis, pneumonia, pharyngitis, peritonsillar/retropharyngeal abscess)
  • Systemic viral syndrome
  • Infectious mononucleosis (Epstein-Barr virus [EBV], cytomegalovirus [CMV])
  • Urinary tract infection (UTI)
  • Bone or joint infection
  • Enteric infection (Salmonella, Yersinia enterocolitica, Yersinia pseudotuberculosis, Campylobacter jejuni)
  • Cat-scratch disease
• Less common infectious causes
  • Tuberculosis (TB)
  • Lyme disease
  • Rickettsial disease (Rocky Mountain spotted fever, ehrlichiosis, anaplasmosis)
  • Malaria
  • CNS infection (bacterial or viral meningoencephalitis, intracranial abscess)
  • Dental or periodontal abscess
  • Subacute bacterial endocarditis (SBE)
  • HIV infection
  • Human herpes viruses
  • Acute rheumatic fever
• Other infectious causes
  • Q fever
  • Brucellosis
  • Toxoplasmosis
  • Syphilis
  • Parvovirus B19
  • Endemic fungi (histoplasmosis, blastomycosis, coccidioidomycosis)
  • Psittacosis
  • Typhoid (Salmonella spp.)
  • Chronic meningococcemia
• Possible noninfectious causes
  • Collagen vascular disease (systemic juvenile idiopathic arthritis [JIA], systemic lupus erythematosus, dermatomyositis, sarcoidosis, vasculitis syndrome)
  • Malignancy
  • Kawasaki syndrome
  • Inflammatory bowel disease (IBD)
  • Drug fever
  • Hyperthyroidism
  • Factitious fever or Munchausen syndrome by proxy
  • Centrally mediated fever
  • Periodic fever syndromes
  • Kikuchi-Fujimoto disease (histiocytic necrotizing lymphadenitis)