Severe Legionella pneumophila infection in a patient with hairy cell leukemia in partial remission after alpha interferon treatment

Legionella pneumonia is an increasingly frequently reported complication in immunocompromised patients, particularly patients with hairy cell leukemia (HCL) in active phase. The most important predisposing factor seems to be the quantitative and qualitative defect of the monocytic-macrophagic system characteristic of HCL. We report a case of severe Legionella pneumophila infection with multisystem involvement in a patient with HCL in stable partial remission obtained after therapy with interferon. In our patient recovery of a normal monocyte count did not protect against a legionella infection, indicating that this pathogen should always be sought in HCL patients even those in clinical and hematologic remission. Early diagnosis and appropriate treatment may reduce the mortality of this serious complication.