Legionellosis in children with leukemia in relapse.

Two children with legionellosis complicating a relapse of acute lymphoblastic leukemia are reported. A 5-year-old boy with pneumonia had Legionella pneumophila cultured from a tracheal aspirate following a rapid deterioration in his respiratory status and intubation. This child had severe and irreversible granulocytopenia and died in spite of therapy with erythromycin and rifampin added five days later. Combination antimicrobial therapy is suggested for immunosuppressed children with legionellosis if resolution of neutropenia is not readily anticipated. Culture of Legionella sp from respiratory tract secretions or sputum, as reported for the first time in the pediatric literature, should be attempted in all children in whom this infection is suspected. A 13-year-old boy with pneumonia recovered in spite of therapy with antimicrobial agents not proven to be effective against the legionellae. Clinical improvement coincided with increase in absolute granulocyte count. A retrospective diagnosis was made when seroconversion to Legionella micdadei (less than 1:16 to 1:1,024) was determined during a survey of unselected sera from 255 hospitalized children. This is the first documented case of Pittsburgh pneumonia described in a child.