Non-specific interstitial pneumonia and Chlamydia pneumoniae infection.

Recently, the clinical features of non-specific interstitial pneumonia (NSIP) have been described. We hypothesize that recurrent infection caused by Chlamydia pneumoniae may play a role in the pathogenesis of NSIP. To prove this, we quantified serum IgA and IgG antibodies against C. pneumoniae using the enzyme linked-immunosorbent assay kit. The study included 15 patients diagnosed with NSIP, 20 patients with chronic obstructive pulmonary diseases (COPD) as disease group, and 27 control subjects. IgA antibody against C. pneumoniae was positive in 12 of 15 patients with NSIP, in 16 of 20 patients with COPD, and in 14 of 27 control subjects. IgG antibody against C. pneumoniae was positive in 14 of 15 patients with NSIP, in 17 of 20 patients with COPD, and in 16 of 27 control subjects. If the cut off value (mean +/- 2SD, index more than 3.0) was introduced, IgA and/or IgG antibodies against C. pneumoniae were positive in 8 of 15 patients with NSIP (53.3%), in 9 of 20 patients with COPD (45%), and in 2 of 27 control subjects (7.4%). These results suggest that infection of C. pneumoniae might play a role in the pathogenesis of NSIP.