Abstract
Patients with a compromised immune system suffer a wide variety of insults. Pulmonary complications remain a major cause of both morbidity and mortality in immunocompromised patients. When such individuals present with radiographic infiltrates, the clinician faces a diagnostic challenge. The differential diagnosis in this setting is broad and includes both infectious and non-infectious conditions. Evaluation of the immunocompromised host with diffuse pulmonary infiltrates can be difficult, frustrating, and time-consuming. This common and serious problem results in significant morbidity and mortality, approaching 90%. Infections are the most common causes of both acute and chronic lung diseases leading to respiratory failure. Non-invasive diagnostic methods for evaluation are often of little value, and an invasive procedure (such as bronchoalveolar lavage, transbronchial biopsy or even open lung biopsy) is therefore performed to obtain a microbiologic and histologic diagnosis. Bronchoscopy allows certain identification of some aetiologies, and often allows the exclusion of infectious agents. Early use of computed tomography scanning is able to demonstrate lesions missed by conventional chest X-ray. However, even when a specific diagnosis is made, it might not impact patient's overall survival and outcomes.