Fever of Unknown Origin

Question 1

Fever of Unknown Origin

Answer 1

• A documented fever of >100 degrees rectal or 101 oral for 2-3 weeks without etiology that includes 3wk of outpatient visits, extensive studies, and continued fevers
• No etiology after 1wk of evaluation in hospital
• Fever causing agents produce endogenous pyrogens that reset the hypothalamic center
• In infants <3mo with fever, 70% of causative agents can be identified, the majority being viral.
• A workup for bacterial causes is still needed

Question 2

FoUO: causes

Answer 2

• Atypical presentations of common infections
• Some reflect rheumatic or connective tissue disease
• Neoplastic conditions must be considered

Question 3

FoUO: Origin

Answer 3

• Diagnostic and management challenge
• Febrile infants <6, the most common causes include UTI, abscess, and osteomyelitis
• In adolscents, most common causes include: TB, IBD, and lymphoma

Question 4

FoUO: Dx

Answer 4

• Labs: CBC-diff, CRP/ESR, CMP, TSH, Blood cultures, UA, CSF protein and glucose tests including culture, PPD, serum protein analysis, EBV panel (may get - MonoSpot); ANA
• Imaging: Chest/sinus/GI x-rays; CT; MRI; Echo; US
• Procedures: Bone marrow biopsy

Question 5

Infants: 29-90d

Answer 5

• At risk for developing a variety of invasive bacterial infections, including prenatally acquired organisms (i.e. GBS), or infections acquired in the household (i.e. pneumococcal, meningococcal)
• Divide those that appear toxic and those that do not
• Viral illness is the most common cause of fever in this age group if there is evidence of viral disease (URI, bronchioloitis) and the infant is not toxic
• UTI is the most common bacterial infection in this age group
• Toxic children should be admitted
• Non-Toxic = previously healthy; no focal infection; WBC 5K-15K, without left shift; NL UA; and, when diarrhea is present, <5WBC/HPF and negative gram stain on stool sample can be followed as outpatients

Question 6

Infants: 3-36mo

Answer 6

• Urine cultures should be considered in all male patients younger than 6mo and in all females 102.2 and WBC >15K
• Chest XR may be considered with WBC >20K without increased work of breathing

Question 7

Tx of Fever

Answer 7

• Assure parents that fevers 102.2 (39 C) or are uncomfortable
• IBU can be used if 6mo+
• ASA should not be used for treating fever in any child or adolscent due to risk of Reye’s Syndrome