Day #45 - Fever of Unknown Origin Redux

Today we discussed a very complicated (perhaps too complicated) case of a patient with fever of unknown origin, pancytopenia with granulomas in the bone marrow, probable disseminated intravascular coagulation, altered mental status and abnormal liver function.

The consultant, an infectious diseases specialist, went through a very broad differential diagnosis which I will attempt to re-create for you.

Non-infectious:

• Hematologic malignancy
• Non-hematologic malignancy (i.e. renal cell carcinoma)
• Venous thromboembolism
• Inflammatory:
  
  • Vasculitis -- i.e. temporal arteritis
  • Collagen Vascular Disease -- i.e. SLE
    
• Endocrine -- i.e. hyperthyroidism
• Periodic Fever Syndromes
• Factitious fever

Infectious:

• Viral:
  
  • HIV, EBV, CMV, influenza, measles/mumps, other.
• Bacterial:
  
  • Endocarditis, occult abscess, osteomyelitis from various pathogens
  • Unusual bacterial causes (see below)
    
• Fungal:
  
  • Endemic fungi such as:
    
    • Histoplasmosis (Ohio river valley, St. Laurence River Valley, Montreal in 1960s, Caves w/bats)
    • Blastomycosis (Northwestern Ontario)
    • Coccidiomycosis (Southwestern US)
• Mycobacterial
• Parasitic -- i.e. malaria (usually non-falciparum), babesiosis

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Unusual bacterial causes

Some of these were discussed today:

• Rat-bite fever
• Meilodosis (travel to Australia, Southeast Asia)
• Plague
• Brucellosis (travel, exposure to sheep, cattle, goats, unpasturized cheese)
  
• Bartonella Henselae (Cat Scratch Disease)
• Q-Fever (Sheep, Pregnant Cats, high rates in Nova Scotia)

The key is the travel and exposure history and an open mind.