Mycoplasma pneumoniae respiratory tract infection prevailing among infants at a nursery school

: Mycoplasma pneumoniae (M. pneumoniae) infection in infants had been considered to be very rare, but recently some clinical cases have been reported. We experienced an epidemic of M. pneumoniae infection in a nursery school, and compared M. pneumoniae infection in infants with that in preschool and school children to investigate the features of infantile M. pneumoniae infection. We obtained the following clinical findings in 15 infantile patients with M. pneumoniae infection: The maximum body temperature scarcely increased to 38.5 degrees C or more and the period of high temperature and cough was shorter in infant patients than in preschool and school aged patients. Stridor occurred in 4 patients but skin disorder was not observed. In the laboratory findings, the white blood cell count tended to increase with no changes in neutrophil/lymphocyte ratio and CRP increased slightly. M. pneumoniae antibody was negative in all the patients except 3 and old hemagglutination tests were positive in only 4 patients. The chest X-ray examinations showed a mild increase in the hilar shadow. However, the sequentially located homogeneous shadow which is commonly seen in preschool and school aged patients was not detected. M. pneumoniae antibody scarcely increased in infantile patients but M. pneumoniae was isolated by throat culture from 14 of the 15 patients who were diagnosed as having M. pneumoniae infection.