Fever in the Immunosuppressed Patient

Today we talked about fever in a patient with a history of AML after completion of chemotherapy. We spoke about the importance of maintaining our natural barriers (mucosal, skin, nails) in defence of pathogens. Here are some important points we touched on:

1) Types of immunity:

• Innate: 
• Parts of the immune system able to respond to insults immediately, not reliant on antibodies or other acquired mechanisms
• Acquired:
• Cellular: Mediated largely by T cells. Important for intracellular pathogens (mycobacterium, fungal infection, viruses, some bacteria, parasites)
• Humoral: immunologic responses mediated by antibodies (from B-cells and T helper cells) Important for defence against encapsulated bacteria
• Our patient had AML with post chemotherapy bone marrow suppression and severe neutropenia. Therefore she had suppression of both her innate and acquired immune system.

2) Mucositis/Esophagitis

• Bacterial translocation: 
• Gram positives: Strep viridans and milleri. The S. milleri group can survive under low oxygen tension and is "abcessogenic"
• Anaerobes: Fusobacterium (associated with internal jugular thrombophlebitis AKA Lemierre's syndrome)
• Gram negatives: institutionalized/sick patients may develop colonisation of the Upper GI tract with lower GI tract commensals, putting them at risk of gram negative bacteremia. Consider Pseudomonas aeruginosa, Enterobacteriacea, Enterococcus.
• Fungal
• Candida
• Fluconazole: activity limited to yeasts and some endemic fungi (histoplasma, blastoomyces, coccidioides and paracoccidioides). Excellent activity against Candida albicans, but less against non-albicans.
• Itraconazoel: Broader spectrum than fulconazole. Including endemic fungi, sporothrix schenckii and aspergilus.
• Voriconazole: enhanced activity against aspergillus and other hyalohyphomycoses. Superior to fluconazole resistent C. glabrata dn C. krusei.
• Posaconazole: expanded spectrum with activity against mucorales, yeasts and molds.


• Viral
• HSV, CMV

3) Aspergillosis

• Invasive aspergillosis: Diagnosis based on culture of aspergillosus with histopathologic evidence of invasive hyphae or culture from a normally sterile site. Galactomannan or Beta D glucan assay can also be used to determine invasive aspergillosis.
• Chronic pulmonary aspergillosis: Four types: aspergilloma, chronic cavitary pulmonary aspergillosis, chronic fibrosing pulmonary aspergillosis, chronic necrotizing pulmonary aspergillosis.