Pulmonary Fungal Infections

John W. Baddley, M.D. Peter G. Pappas, M.D.

There have been many advances in the field of medical mycology in the past decade, including new antifungal therapies, diagnostic tools, and strategies for prevention and treatment. Despite these advances, fungal infections continue to increase in incidence in many populations, and may be associated with pronounced morbidity and mortality. The epidemiology of invasive fungal infections continues to emerge, underscoring the need for prompt recognition and treatment of these infections in order to achieve optimal patient outcomes.

Advances in medical care over the past several decades have led to an increasing number of immunocompromised patients at risk for fungal infections. Pulmonary fungal infections continue to occur in traditional risk groups, such as those with human immunodeficiency virus (HIV) infection, patients receiving prolonged corticosteroids, patients with underlying malignancy or those who have received hematopoietic stem cell or solid organ transplants. In addition, there are several emerging groups at risk, including intensive care unit (ICU) patients, patients with chronic obstructive pulmonary disease (COPD) and patients on newer immunosuppressive therapies, such as TNF-α inhibitors or other immunomodulating agents.

Moulds are important pulmonary pathogens, with Aspergillus species causing the greatest number of clinically significant infections; however, other less common moulds such as Scedosporium, Fusarium, agents of mucormycosis and dematiaceous (pigmented) moulds are increasingly important pulmonary pathogens. Cryptococcus neoformans remains one of the most common yeast pathogens; and importantly, there has been an emergence of C. gatti pulmonary infections in parts on the Northwest United States and Canada. The traditional “endemic” mycoses, including histoplasmosis, blastomycosis, coccidioidomycosis, penicilliosis and paracoccidioidomycosis remain important causes of pulmonary fungal infections in endemic regions, where outbreaks of these infections are reported frequently. Moreover, the increased mobility of modern society makes it imperative that clinicians have some working knowledge of these infections outside of their traditional geographic range.

A major advance in the field of clinical mycology has been directed at efforts towards improving diagnostic testing. Beyond traditional histopathology and culture techniques, newer molecular tests have come to the aid of the clinician, leading to earlier diagnosis and aggressive initial therapy in selected conditions. For example, the use of EIA aspergillus galactomannan testing has become standard for many patients with stem cell transplants and other high risk groups. In addition, the less specific β-D-glucan assay is available and has become an important modality in the diagnosis of pneumocystosis, invasive candidiasis, and other mycoses. Finally, PCR testing for multiple pulmonary fungal pathogens has been developed and has proven useful in some clinical studies. Unfortunately, the diagnosis of many fungal infections still relies heavily on clinician suspicion, knowledge of risk factors, clinical presentation, radiographic features, and/or a history of relevant exposure. Awareness of the epidemiology of pulmonary fungal infections continues to be an important clinical tool.

This issue of Seminars in Respiratory and Critical Care Medicine is devoted to pulmonary fungal infections among multiple host groups. Current state-of-the art reviews are presented by internationally recognized experts in the field. We believe that the information contained herein will serve as a useful resource for both the younger and the more seasoned clinician in the diagnosis and management of these complex disorders.