Legionnaires' disease combined with erythema multiforme in a 3-year-old boy.

A case of Legionnaires' disease (LD) is described in a 3-year-old boy. He had fulminant disease with typical signs like bilateral pneumonia, gastrointestinal symptoms, and somnolence indicating involvement of the central nervous system. There was no premorbidity. An outstanding development was erythema multiforme, which has never previously been described in LD. The basic disease was caused by Legionella pneumophila. This is evidenced by specific serum IgM at admission and a subsequent significant rise in titers against L. pneumophila. At an early stage respiratory syncytial virus (RSV) was isolated from the patient's throat, although there was no antiviral serological response at the outset of erythema multiforme or 3 weeks after onset of disease; anti-RSV appeared later. The prolonged course of the disease can be explained by the successive occurrence of two infections. The possibility that the virus could have contributed to the development of erythema multiforme cannot be ruled out. The role of concomitant medication cannot be separated out, but on the basis of general knowledge of their immunogenicity and the fact that immunosuppressive cortisone was given at the time it is less likely that the antibiotics contributed significantly.