Legionellosis must be kept in mind in case of pneumonia with lung abscesses in children receiving therapeutic steroids.

A 10-year-old boy, who had received recurrent short-course treatments with steroids to control severe autoimmune thrombocytopaenia, developed Legionnaires' disease as community-acquired pneumonia. Legionella pneumophila pneumonia was complicated by an extended abscess of the right inferior lobe, leading to residual lung cavities. Legionellosis must be kept in mind as the differential diagnosis in the case of severe pneumonia and with lung abscesses in children receiving therapeutic steroids. Legionella-specific diagnostic tests (polymerase chain reaction [PCR] in respiratory samples or urine antigen assay) and, also, specific empirical antibiotic combination therapy are required for the early detection and treatment of L. pneumophila pneumonia in childhood.