Fungal Infections, Blood and Bone Marrow Features



Fungal Infections, Blood and Bone Marrow Features


Mohammad A. Vasef, MD





Key Facts


Terminology



  • Disseminated fungal organisms detected by morphologic review or special stains or by culture


Etiology/Pathogenesis



  • Barrier disruption due to chemotherapy


  • Host defense impairment


  • Organ transplant recipients


  • Patients with AIDS/other immunodeficiency


  • Prolonged neutropenia of any cause


  • Environmental contamination


  • Prolonged usage of broad spectrum antibiotics


  • Central venous line


  • Corticosteroids or radiation therapy


Microscopic Pathology



  • Well-formed or ill-defined granulomas can be identified in bone marrow biopsy sections


  • Sheets of histiocytes with intracytoplasmic fungal organisms without granuloma formation in immunocompromised patients


  • Fungal organisms are best detected on Wright-stained bone marrow aspirate smears


  • Special stains, including GMS &/or PAS, may be required for identification of organisms


  • Fungal organisms, such as Histoplasma and Candida, occasionally are seen as intracytoplasmic inclusions within neutrophils &/or monocytes in peripheral blood smears



    • Particularly in AIDS patients with low CD4 count






Peripheral blood smear feather edge shows intracytoplasmic Candida yeast forms predominantly within neutrophil cytoplasm. Note the capsule and dense appearance of Candida yeast forms image.






Peripheral blood smear shows extracellular pseudohyphae image and yeast forms image of Candida fungal organisms.


TERMINOLOGY


Synonyms



  • Systemic fungal infections


Definitions



  • Disseminated fungal organisms detected in blood or bone marrow morphologically or by special stains or via culture


ETIOLOGY/PATHOGENESIS


Pathogenesis



  • Host defense impairment


  • Patients at high risk for systemic fungal infections include



    • Bone marrow or organ transplant recipients


    • Patients with AIDS, human immunodeficiency virus (HIV), or other immunodeficiency-related states


    • Patients receiving potent chemotherapy, radiation therapy, or corticosteroids therapy


  • Other factors making patients susceptible to fungal infections



    • Prolonged neutropenia of any cause


    • Environmental contamination


    • Total parenteral nutrition


    • Prolonged use of broad spectrum antibiotics


    • Central venous catheters


    • Barrier disruption due to chemotherapy


CLINICAL ISSUES


Presentation



  • Fever of unknown origin in vast majority of patients



    • Prolonged neutropenia


    • Bone marrow or solid organ transplantation


    • Human immunodeficiency virus (HIV) infection


    • Radiation therapy


    • Corticosteroids therapy


  • Common systemic fungal infections involving peripheral blood &/or bone marrow in solid organ transplantation patients



    • Candida species


    • Histoplasma capsulatum


    • Aspergillus species


    • Zygomycosis



      • Poor prognosis without early aggressive treatment


      • Resistant to most antifungal agents


  • Common systemic fungal infections involving peripheral blood &/or bone marrow in patients with AIDS



    • Histoplasma capsulatum


    • Coccidioides immitis


    • Disseminated Pneumocystis jirovecii with bone marrow involvement (rare case reports)


    • Penicillium marneffei, mainly reported in China



      • Can be confused with Histoplasma capsulatum due to morphologic similarity


Laboratory Tests



  • Careful morphologic review of Wright-stained peripheral blood and bone marrow aspirate smears


  • Special stains for fungal organisms, including GMS and PAS on bone marrow biopsy sections


  • Bone marrow &/or blood culture


  • Fungal antigen detection in serum by RIA


  • Molecular methods, including PCR and nucleic acid sequence-based amplification (NASBA)


Treatment



  • Drugs



    • Amphotericin B


    • Itraconazole or posaconazole prophylaxis

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Jun 13, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Fungal Infections, Blood and Bone Marrow Features

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