Co-infection with Legionella pneumophila and Pneumocystis carinii in a patient with chronic lymphocytic leukemia.

A patient with chronic lymphocytic leukemia was found to have pneumonitis caused by a simultaneous Pneumocystis carinii and Legionella pneumophila infection. Although both microorganisms frequently cause pulmonary infections in immunocompromised patients, co-infection has not been reported. This patient responded to antimicrobial therapy, but superinfection with Candida albicans led to his death. As there are numerous infective and noninfective causes of pneumonia in such patients, this case illustrates that the identification of a single etiologic agent does not obviate the search for other potential causes.