⚠️ Must-Not-Miss Diagnoses
Sepsis/septic shock, bacterial meningitis, necrotizing fasciitis, endocarditis with embolism, malaria in returning traveler, neutropenic fever, toxic shock syndrome.
Differential Diagnosis by Key Features
| Clinical Feature | Think Of | Priority |
|---|---|---|
| Fever + altered mental status + hemodynamic instability | Sepsis | HIGH — 1-hour bundle |
| Fever + headache + stiff neck + photophobia | Bacterial meningitis | HIGH |
| Fever + skin pain out of proportion, wooden texture, rapid spread | Necrotizing fasciitis | HIGH — surgical emergency |
| Fever + new murmur + embolic phenomena, IVDU | Endocarditis | HIGH |
| Immunocompromised + fever | Neutropenic fever / opportunistic infection | HIGH |
| Recent travel to endemic area + cyclical fever, splenomegaly | Malaria | High |
| Productive cough + localized crackles + infiltrate | Pneumonia | Moderate |
Systematic Approach
Assess
Sepsis screen first
Any febrile patient with tachycardia, hypotension, altered mental status, or tachypnea should be screened for sepsis. qSOFA (RR≥22, altered mentation, SBP≤100) is a rapid bedside screen. Lactate and blood cultures before antibiotics.
Source
Systematic source identification
LUST: Lungs (pneumonia), Urine (UTI/pyelonephritis), Skin/Soft tissue (cellulitis, NF), Tubes/lines (catheter-related). Also consider: CNS (meningitis), abdomen (cholecystitis, appendicitis), heart (endocarditis), joints (septic arthritis).
History
Travel, exposures, immune status, medications
Recent travel (malaria, typhoid, dengue), animal exposures (zoonoses), sexual history (STIs), immunosuppression (opportunistic infections), recent antibiotics (C. diff), medications (drug fever).
Exam
Focused on source identification
Skin exam crucial — rash can diagnose meningococcemia, Rocky Mountain spotted fever, endocarditis (Janeway lesions, Osler nodes). Splenomegaly suggests malaria, EBV, or endocarditis. Meningismus → LP. Joint effusion → arthrocentesis.
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