Persistence of Pneumocystis carinii in lung tissue of acquired immunodeficiency syndrome patients treated for pneumocystis pneumonia.

Eleven patients with acquired immunodeficiency syndrome (AIDS) and Pneumocystis carinii pneumonia (PCP) were studied by repeat bronchoscopy during PCP treatment to assess histologic evidence of resolution of the pneumonia. Nine of 10 patients studied after 8 to 21 days of therapy demonstrated evidence of persistent PCP. Four of 6 patients studied after 22 to 35 days of therapy continued to demonstrate Pneumocystis carinii cysts on repeat examination, while only 1 of 4 patients studied after 35 days of therapy showed evidence of PCP pneumonia. The rate of resolution of PCP in patients with AIDS may be different from the rate of resolution of PCP in patients without AIDS. There was no apparent correlation between rate of clinical response and likelihood of histologic resolution on follow-up biopsy. The PCP in patients with AIDS may require more prolonged therapy for complete resolution of this pneumonic process.