Rare and Emerging Fungal Pulmonary Infections

Jay B. Varkey, MD; John R. Perfect, MD

Disclosures

Semin Respir Crit Care Med. 2008;29(2):121-131. 

In This Article

Yeastlike Fungi

Trichosporon

Trichosporon has been isolated from soil, water, and plants and can also be found colonizing human skin. After recent changes in taxonomy, six species of Trichosporon have been associated with human disease. Trichosporon cutaneum and Trichosporon asteroides are associated with superficial cutaneous infections. White piedra of the scalp is caused by Trichosporon ovoides, and a similar disease of the pubic hair is caused by Trichosporon inkin.

Deep invasive and disseminated infection can occur in highly immunocompromised persons and is typically caused by Trichosporon asahii and Trichosporon mucoides. The illness is acute and often manifested by fever and multiple red papular skin lesions. Trichosporonosis affects multiple organs, including the lungs; however, pneumonia is not a consistent feature of the illness. Chronic hepatic trichosporonosis mimics hepatic candidiasis and may be seen in persons with recovery of their neutrophil counts following chemotherapy.[2] Renal involvement is common and can be associated with hematuria and funguria. In persons with prosthetic heart valves, fungal prosthetic valve endocarditis has been described. Diagnosis of disseminated infection is often made by biopsy -- in the absence of visible arthroconidia, the mixture of hyphae, pseudohyphae, and budding yeasts seen on histopathology often resembles Candida. In severe cases of trichosporonosis, fungemia is detected.

Trichosporonosis is associated with high mortality rates. The minimum inhibitory concentration (MIC) obtained for the echinocandins is very high; these agents should not be used to treat trichosporonosis. Amphotericin B has been recommended, but in vitro resistance and clinical failures have been reported.[60] Trichosporon species are usually susceptible in vitro to fluconazole, itraconazole, voriconazole, and posaconazole.[61,62]

Geotrichum

Geotrichum species are widely distributed in nature and have been isolated from soil, water, air, sewage, plants, cereals, and dairy products.[63] One related species, Blastoschizomyces capitatus, is the most prominent fungus in this group to produce disseminated infections in immunocompromised hosts.[64] These species have also been found in normal human flora such as sputum and feces. Disseminated infection such as Geotrichum candidum occurs in immunocompromised persons and is typically marked by skin lesions and fungemia.[65] Blood cultures are usually positive. As with Trichosporon, a chronic disseminated form of Geotrichum infection, similar to chronic disseminated candidiasis, may be seen in persons with resolving neutropenia.[66] Bronchial and pulmonary infection have been reported but must be differentiated from colonization of the respiratory tract, which is probably a more common clinical situation.

The optimal approach to therapy is not yet defined. Although in vitro susceptibility testing has demonstrated decreased antifungal activity to amphotericin B, clinical results have been promising with or without flucytosine or high-dose fluconazole.[67] Voriconazole yields very low MICs against Geotrichum species and may represent first-line therapy.[68] In cases of fungemia, central venous catheters should probably be removed.

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