Chlamydia trachomatis infant pneumonitis: comparison with matched controls and other infant pneumonitis.

We determined the prevalence of Chlamydia trachomatis infection in 30 consecutive hospitalized infants less than six months of age with pneumonitis and in 28 matched controls (nine of 30 vs. one of 28. P less than 0.05). In comparing 16 cases of pneumonitis due to C. trachomatis with 27 not due to that agent, we found several distinguishing clinical and laboratory features: C. trachomatis was highly correlated with radiographic hyperinflation, prolonged cough and congestion, greater than or equal to 400 eosinophils per cubic millimeter and serum lgG greater than or equal to 500 and lgM greater than or equal to 110 mg per deciliter. C. trachomatis was responsible for 13 of 21 cases seen at three to 11 weeks vs. three of 22 seen at other ages. Antibody to C. trachomatis in tears (13 of 14 vs. two of 27), nasopharynx (12 of 14 vs. one of 27) and blood (16 of 16 vs. two of 23) was specific for C. trachomatis pneumonitis. C. trachomatis is prevalent among hospitalized infants with pneumonitis. Conjunctival infection precedes C. trachomatis pneumonitis more commonly than has previously been thought.