Emerging Fungal Pathogens in Immunocompromised Patients: Classification, Diagnosis, and Management

Abstract

Fungi such as Fusarium species, Trichosporon species, Curvularia species, and Alternaria species previously were thought to represent contamination or harmless colonization when isolated from immunocompromised patients. More recently, the pathogenic role of these and other fungi has been clearly established. Three diverse groups of fungi are responsible for these emerging infections: the agents of phaeohyphomycosis and hyalohyphomycosis and certain yeasts. Reports of the emergence of these organisms as significant pathogens may be ascribed to increasing awareness by physicians and microbiologists, aggressive culture of patient specimens, increasingly cytotoxic chemotherapy, and selection of resistant organisms by the widespread empirical use of amphotericin B. Infections with these fungi tend to be disseminated and are frequently fatal in immunocompromised hosts. Treatment of these infections is not standardized. Experimental therapy in murine models of fungal infections suggests a role for newer agents, combination antifungal chemotherapy, and immunotherapy.

Atypical skin lesions caused by Curvularia sp. and Pseudallescheria boydii in two patients after allogeneic bone marrow transplantation

“…1,2 Three diverse groups of fungi are responsible for these infections: hyalohyphomycoses, phaeohyphomycoses and certain yeasts. 2 Hyalhyphomycosis encompasses mycoses caused by molds whose basic tissue form is that of branched or unbranched hyaline, light-colored, hyphal elements without pigment in their cell walls. Important human pathogens are Fusarium, Penicillium and Pseudallescheria boydii.…”

“…Important human pathogens are Fusarium, Penicillium and Pseudallescheria boydii. 2 Pseudallescheria boydii is the heteromorph or sexual state of a cosmopolitan fungus whereas Scedosporium apiospermun is the anamorph or asexual state. 2 In immunocompromised hosts Pseudallescheria boydii can cause sinusitis, pneumonia and endophthalmitis and has a tendency for dissemination and involvement of the central nervous system.…”

“…2 Pseudallescheria boydii is the heteromorph or sexual state of a cosmopolitan fungus whereas Scedosporium apiospermun is the anamorph or asexual state. 2 In immunocompromised hosts Pseudallescheria boydii can cause sinusitis, pneumonia and endophthalmitis and has a tendency for dissemination and involvement of the central nervous system. [4][5][6][7] Pheohyphomycoses are fungal infections caused by darkly pigmented fungi (colour imparted by melanin in the cell walls).…”

“…The four genera most frequently encountered in humans are Curvularia, Bipolaris, Exserohilum and Alternaria. 2 Although cases of Curvularia infection in immunocompetent hosts involving the lung, sinuses, endocardium, skin, subcutaneous tissues, liver, spleen and cornea have been described, infections in immunocompromised hosts have been reported only occasionally. 8,9 The first patient, who had a localized Fusarium infection during her first transplant, developed a second fungal infection caused by Pseudallescheria boydii with multiple hemorrhagic vesicles during the second transplant.…”

“…are the most common fungal pathogens in this setting although new fungal opportunists (hyalohyphomycoses and phaeohyphomycoses) may occasionally be isolated and identified as being responsible for local or systemic infections. 2,3 The purpose of this report is to describe the clinical manifestations and the mycological findings of two patients after allogeneic BMT who developed atypical skin lesions caused by unusual opportunistic fungi. …”