Pulmonary Fungal Infections in the Immunocompetent Host

Pulmonary fungal infections, which have traditionally been associated with patients who are immunocompromised, are now increasingly recognized among immunocompetent individuals. This trend is attributable to multiple factors including altered environmental conditions linked to climate change, postviral syndromes, and advances in ICU practices. Immunocompetent hosts typically generate effective responses to pulmonary fungal infection; however, severe disease may develop in the presence of abnormal lung structure or function, transient immune dysfunction, or antigenic hypersensitivity.

The absence of traditional risk factors for impaired immunity is generally associated with a low clinical suspicion of fungal infection. Prompt recognition of pulmonary fungal disease in the immunocompetent host poses numerous challenges due to a nonspecific clinical presentation or lack of characteristic radiographic features. Readily available noninvasive biomarkers such as serum galactomannan have limited sensitivity in nonneutropenic hosts, whereas the sensitivity and performance characteristics of (1-3)-ß-D-glucan are dependent on the etiologic fungal pathogen and clinical context. Invasive sampling is frequently required for disease confirmation; however, conventional microbiological testing of these specimens remains slow and insensitive. Therefore, a high index of suspicion and appropriate diagnostic testing are crucial for the accurate and timely diagnosis of pulmonary fungal infection, especially when no alternative diagnosis is evident or when there is a poor clinical response to treatments targeting other diseases.

An organized clinical approach that integrates epidemiologic and novel risk factors with the strengths and limitations of available diagnostic testing is critical for effective diagnosis and management of pulmonary fungal infections in immunocompetent hosts.