📊 Definition
• Fever >38.3°C (101°F) for ≥8 days
• No diagnosis after initial H&P and preliminary labs
• Infections cause ~50%, autoimmune ~20%, malignancy ~10%, no diagnosis 10-20%
• Outcome better than adults
🦠 Infectious Causes (Most Common)
• Occult infections: endocarditis, osteomyelitis, abscess (intra-abdominal, pelvic, dental), EBV/CMV, TB, atypical mycobacteria, Lyme, cat-scratch, toxoplasmosis, brucellosis, tularemia, leptospirosis, malaria
• Relapsing fever pattern: malaria, Lyme, rat-bite fever
🩺 Autoimmune/Inflammatory
• Systemic-onset JIA (Still disease): quotidian fevers (once/twice daily), salmon-pink rash, arthritis (may be late)
• SLE, inflammatory bowel disease, sarcoidosis, Kawasaki disease (incomplete)
• Periodic fever syndromes: familial Mediterranean fever (FMF), TRAPS, HIDS, PFAPA (periodic fever, aphthous stomatitis, pharyngitis, adenitis)
📋 Malignancy & Other
• Leukemia, lymphoma, neuroblastoma, Wilms tumor
• Factitious fever: intentional (caregiver-fabricated illness) or unintentional (thermometer manipulation, skin heating)
• Drug fever, factitious fever, central fever (brain damage, dysautonomia)
📌 Decision strategy: Extensive history (travel, animal exposure, medications, family history). Initial labs: CBC, ESR/CRP, blood cultures, LFTs, UA, CXR, TB test. If unrevealing → ANA, RF, immunoglobulins, ferritin (systemic JIA), echocardiogram (endocarditis), advanced imaging (CT/MRI).