Fatal legionellosis in patients with malignant hematologic diseases.

Pneumonia was present in 70/157 (44.6%) autopsied patients with malignant hematologic diseases. In 16/70 patients (22.9%), legionellae were found to be the causative agents by screening lung tissue specimens with the direct fluorescent antibody method. In 5/16 patients with Legionella pneumonia, in whom legionellosis had been suspected clinically, the diagnosis had already been established by serology, urinary Legionella antigen detection, and culture. These results provide evidence that legionellosis is an important pneumonia etiology in patients with malignant hematological diseases. Thus, Legionella diagnostics should be applied routinely, and antibiotics effective in the treatment of legionellosis should be added to the usual therapy in patients with etiologically unexplained pneumonias. In view of the common occurrence of relapses of Legionella pneumonia, antibiotic therapy should be continued for an extended period.