Preventive effect of sulfamethoxasole-trimethoprim on Pneumocystis jiroveci pneumonia in patients with interstitial pneumonia

Background Pneumocystis jiroveci pneumonia (PCP) is a potentially fatal complication in interstitial pneumonia patients receiving glucocorticoid therapy. Prophylaxis of PCP during glucocorticoid therapy is an important issue in the treatment of interstitial pneumonia. Objective We evaluated the prophylactic effect of sulfamethoxasole-trimethoprim (TMP-SMX) in interstitial pneumonia patients receiving glucocorticoids. Methods We retrospectively analyzed 74 interstitial pneumonia patients who received glucocorticoid therapy. Results Seven of the 74 patients developed PCP. At the time of diagnosis of PCP, the mean duration of glucocorticoid therapy was 71 days and the mean daily dose of prednisolone was 37 mg. Among the 7 patients, the circulating CD4+ lymphocyte count was 370/mu l on average and it was over 200/mu l in 3 cases. The PCP patients showed a significant reduction of the lymphocyte count at 4 weeks after initiation of steroid therapy. None of the patients who received prophylactic TMP-SMX therapy developed PCP even if the CD4+ lymphocyte count was less than 200/mu l. Conclusion Interstitial pneumonia patients receiving glucocorticoid therapy can benefit from TMP-SMX prophylaxis against PCP. Development of PCP cannot be ruled out in patients with a CD4+ lymphocyte count of greater than 200/mu l.