Fever – Unknown Origin

Fever – Unknown Origin: Excerpt from In A Page: Pediatric Signs and Symptoms

Fever of unknown origin (FUO) is a term that is often misused to describe febrile illness without an obvious etiology or without other symptoms. The definition in different studies is arbitrary, but basically refers to at least 2 weeks of daily documented fever that is unexplained despite repeated physical examinations and initial laboratory investigation, in an immunocompetent host. In approximately 12% of cases an etiology cannot be found.

Differential Diagnosis

• Infections (40%)
  –Infectious mononucleosis (EBV, CMV)
  –Other systemic viral syndromes (e.g., HIV)
  –UTI (e.g., E. coli)
  –Osteomyelitis (e.g., staphylococcus)
  –Upper and lower respiratory infections (sinusitis, mastoiditis, pneumonia)
  –Cat-scratch disease (Bartonella henselae)
  –Tuberculosis, nontuberculous mycobacterial infections
  –Abscess (abdominal or retroperitoneal)
  –CNS infections
  –Endocarditis (subacute)
  –Salmonellosis
  –Lyme disease (Borrelia burgdorferi)
  –Leptospirosis
  –Congenital syphilis
  –Others: Brucellosis, histoplasmosis, leishmaniasis, yersiniosis, Q fever (Coxiella burnetii), Rocky Mountain spotted fever (Rickettsia rickettsii)

• Autoimmune diseases (15%)
  –Rheumatoid arthritis accounts for 3/4 of FUO due to autoimmune diseases
  –Systemic lupus erythematosus
  –Rheumatic fever
  –Vasculitis (e.g., HSP)
  –Sarcoidosis
• Neoplastic diseases (7%)
  –Leukemia/lymphoma accounts for 80% of
  FUO due to malignancies
  –Neuroblastoma
  –Hepatoma
  –Soft tissue sarcoma
• Inflammatory bowel disease (3%)
• Drugs and nutritional supplements (drug fever)
• Factitious fever
• Munchausen by proxy
• Neurologic disorders
  –Familial dysautonomia
  –Central thermoregulatory disorder
  –Head injury
• Hyperthyroidism
• Anhidrotic ectodermal dysplasia
• Diabetes insipidus
• Kikuchi disease

Workup and Diagnosis

• History
  –Differentiate between FUO and multiple febrile
• illnesses that occur in short period of time
  –Daily documentation of fever, onset, duration
  –Weight loss, diet history, medications, sick contacts
  –Animal or tick exposure, travel, foreign contacts
  –Immune status, history of transfusion, surgery
  –FH of autoimmune or neoplastic diseases
• Physical exam
  –Vital signs, growth parameters
  –Skin (rash, desquamation, jaundice)
  –Ophthalmologic exam (conjunctivitis, uveitis)
  –Oral lesions
  –Cardiologic exam (new onset murmur)
  –Abdominal exam (masses, hepatosplenomegaly)
  –Testicular exam
  –Muscle tenderness, bone tenderness, arthritis
  –Lymphadenopathy
  –Neurologic exam
• Labs
  –CBC, ESR, C-reactive protein
  –Renal and hepatic function tests, albumin and globulin
  –Urinalysis, blood and urine culture
  –Viral titers, PPD, cultures for specific organisms, ASO, ANA, bone marrow
• Radiographic imaging with plain films, ultrasound, bone scan, CT scan or MRI of specific organ systems as warranted by the history and physical exam

Treatment

• Specific treatment once diagnosis is made
• Empiric treatment with antibiotics is to be considered only for critically ill patients
• Empiric steroids may be justified only if Still disease is suspected
• Anti-inflammatory agents are sometimes used for a limited period of time and subsequently the patient is observed for recurrence of the fever
• Cessation of offending drugs

Book Source Details

• Book Title: In A Page: Pediatric Signs and Symptoms
• Author(s): Jonathan E. Teitelbaum, Kathleen O. Deantonis, Scott Kahan
• Year of Publication: 2007
• Copyright Details: In A Page: Pediatric Signs and Symptoms, Copyright © 2007 Lippincott Williams & Wilkins.

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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.

More About This Book: Title: In A Page: Pediatric Signs and Symptoms Authors: Jonathan E. Teitelbaum, Kathleen O. Deantonis, Scott Kahan Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 1-4051-0427-9

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