Severe cytomegalovirus pneumonitis in HIV infected patients with higher than average CD4 counts

Background. Cytomegalovirus may replicate within the lungs both of recipients of transplants and of patients infected with the human immunodeficiency virus (HIV). A hypothesis formulated by this group was that a host damaging immune response might be provoked by cytomegalovirus infection and cause a severe pneumonitis in recipients of allogeneic transplants, whereas the progressive impairment of cellular immunity in patients with HIV disease would preclude a damaging immune response in the lungs, and thus protect these patients from severe cytomegalovirus pneumonitis. This study set out to discover whether severe cytomegalovirus pneumonitis arises in HIV infected patients. Methods. Data were prospectively collected on severity of pneumonitis and infectious agents identified in consecutive respiratory episodes in HIV infected patients undergoing diagnostic bronchoalveolar lavage during 20 months. Results. Eighty five episodes of pneumonitis occurred in 68 patients. Cytomegalovirus was identified as the only infectious agent in nine episodes (nine patients). Seven of the episodes were mild; all these patients had CD4 counts below 0.1 x 109/l. The remaining two episodes were severe and ventilatory support was required. In both cases the CD4 counts were above 0.2 x 109/l and HIV infection appeared to have been acquired infection appeared to have been acquired shortly before presentation. Conclusion. Although rare, severe cytomegalovirus pneumonitis may occur in HIV infected patients. Both patients with severe pneumonitis in this series had relatively well preserved immune function. These findings support the hypothesis that severe cytomegalovirus pneumonitis is an immunopathological condition.