Pulmonary infections in the immunocompromised host.

The lung is an organ that is particularly susceptible to infection in the immunocompromised host. Patterns of involvement produced on the chest radiograph include (1) lobar or segmental consolidation; (2) nodules with rapid growth and/or cavitation; and (3) diffuse lung disease. There is a general correlation between the type of radiographic pattern and the microorganism producing the pneumonia. Invasive diagnostic procedures include needle aspiration, transbronchial, and open lung biopsy.