The causes of interstitial pneumonitis in immunocompromised children: an aggressive systematic approach to diagnosis.

A systematic, aggressive approach to the immunocompromised child with interstitial pneumonitis has been used in 24 consecutive patients. Parent and physician awareness of early symptoms and signs had been emphasized. When laboratory data confirmed clinical suspicion, open lung biopsy was done and lung tissue was studied by impression smears, sections, and culture techniques. The etiologic agent was established by stained impression smears within three hours of receipt of tissue in 21 of 24 patients. Eighteen of 24 patients survived. Patients had a poor prognosis if they required ventilatory assistance (five of seven died) or had respiratory symptoms for three days or more prior to biopsy (four of 13 died). Children with solid tumors who had absolute lymphocyte counts less than 500/cu mm, had received chemotherapy and radiotherapy to the chest, and had developed Pneumocystis carinii pneumonitis had a poor outcome (all three died).