›NSAIDs — avoid after 20 weeks gestation (fetal renal effects)
›Glucocorticoids — generally safe; preferred immunosuppression
›Altered presentation in older adults
›Temperature threshold may need adjustment
›Baseline temperature lower in elderly — FUO may present at lower absolute temperatures
›Relative rise > 1.3 C may be clinically significant
›Fewer localizing symptoms
›Infection may present as delirium, falls, or functional decline alone
›Absence of fever does not exclude serious infection
›Blunted fever response in frailty and immunosenescence
›Differential priorities in elderly
›Giant cell arteritis — almost exclusively in patients > 50 years
›ESR > 50 mm/h, jaw claudication, scalp tenderness
›Do not delay prednisone if visual symptoms
›Malignancy — increased incidence with age
›Lymphoma, renal cell carcinoma, colorectal cancer
›Endocarditis — degenerative valvular disease increases risk
›Streptococcus bovis/gallolyticus — associated with colorectal neoplasm
›Medication considerations
›Renal dose adjustment critical
›Vancomycin — target AUC-based dosing, avoid excessive troughs
›Aminoglycosides — high nephrotoxicity risk; minimize use
›Fluoroquinolones — QT prolongation and tendinopathy risk
›Drug fever more likely in polypharmacy context
›Medication review essential in all geriatric FUO
›NSAIDs — avoid; NSAID-induced renal failure and GI bleeding risk elevated
›Imaging adjustments
›FDG PET/CT — evidence of high diagnostic yield in elderly FUO cohorts
›GCA and large vessel vasculitis detected on PET
›FUO definition in children
›Fever >= 38.3 C for >= 3 weeks duration
›Alternative: >= 8 days of daily fever without diagnosis
›Differential differs from adults
›Infection most common cause — Bartonella, Yersinia, Salmonella
›Juvenile idiopathic arthritis (systemic JIA) — most common non-infectious cause
›Malignancy less common than in adults
›Infectious causes in children
›Bartonella henselae — cat scratch disease
›Cat exposure history essential
›Lymphadenopathy with fever
›Epstein-Barr virus
›Infectious mononucleosis — hepatosplenomegaly, exudative tonsillitis
›Salmonella — enteric fever
›Relative bradycardia, rose spots
›Non-infectious causes in children
›Systemic juvenile idiopathic arthritis (sJIA)
›Daily quotidian fever, salmon rash, arthritis
›Macrophage activation syndrome risk — analogous to HLH
›Ferritin markedly elevated
›Kawasaki disease — children < 5 years
›Fever >= 5 days plus four of five criteria
›Conjunctival injection, lip/mucosa changes, rash, extremity changes, lymphadenopathy
›IVIG 2 g/kg IV single dose plus aspirin
›Periodic fever syndromes
›PFAPA — periodic fever, aphthous stomatitis, pharyngitis, adenitis
›Familial Mediterranean fever — autosomal recessive, MEFV gene
›Dosing adjustments in children
›Acetaminophen — 15 mg/kg/dose PO every 4–6 hours (max 75 mg/kg/day)
›Ibuprofen — 10 mg/kg/dose PO every 6–8 hours (max 40 mg/kg/day)
›Ceftriaxone — 50–100 mg/kg/day IV divided every 12–24 hours
›Ampicillin — 200 mg/kg/day IV divided every 6 hours