Pneumonia and lung infections due to emerging and unusual fungal pathogens.

Invasive mold infections affecting the lungs are increasing in incidence and diversity. Severely immunocompromised patients are particularly vulnerable to infection from unusual, normally nonpathogenic fungi that are found naturally in the environment. Certain fungi such as Scedosporium and the dematiaceous fungi also cause lung disease in hosts without overt immune compromise. The impacts of these emerging pathogens range from airway colonization to locally invasive lung, and disseminated, disease. Diagnosis requires isolation and identification of the etiologic agent by either or both phenotypic and molecular biology methods. Evidence of tissue invasion on histopathology is often required to distinguish infection from colonization. Diagnostic imaging techniques are nonspecific, and there are no reliable serological biomarkers of infection. Many rare molds and yeasts demonstrate reduced in vitro susceptibility to antifungal agents. Although amphotericin B formulations remain clinically useful for many of these infections, voriconazole and posaconazole are more effective for some of these difficult-to-treat pathogens. Surgical resection of diseased tissue and support of the host immune system are often required to optimize outcomes.