Immunopathogenesis of Chlamydia pneumoniae Infections in Children

hclamydia pneumoniae is emerging as a frequent ause of respiratory disease in children as well as adults. C. pneumoniae infection in children presents a different set of problems regarding disease presentation and diagnosis compared to adults. Several studies of the role of C. pneumoniae in lower respiratory tract infection in pediatric populations have found evidence of infection in 0 to over 18%. 1-8 Most of these studies have relied entirely on serology for diagnosis. Infection under the age of 5 years has been rare in Seattle and Scandinavia, whereas in a study of Filipino children under the age of 5 years presenting with lower respiratory tract infection, nearly 10% had either acute or chronic antibody to C. pneumoniae. In Brooklyn, the proportion of lower respiratory tract infections associated with C. pneumoniae, as determined by culture, increased from 9% in children under the age of 5 to 19% in the 5-16-year-old age category. Recent studies which have utilized culture have found a poor correlation between culture and serology, especially in children. As part of a multicenter pneumonia treatment study in children 3-12 years of age, Block et al. isolated C. pneumoniae from 34 of 260 (13.1%) of the children enrolled. Serologic evidence of acute infection was found in 48 (18.5%), but only 8 (23%) of the culture positive children met the serologic criteria for acute infection. The serologically positive, culture negative children usually had stable high IgG titers, but no detectable IgM antibody. Most C. pneumoniae infections are probably mild or asymptomatic. Initial reports emphasized mild atypical pneumonia clinically resembling that associated with Mycoplasma pneumoniae. In several subse-