Association of primary Pneumocystis carinii infection and sudden infant death syndrome

To delineate clinical and histological features of the first Pneumocystis c arinii infection affecting the immunocompetent host, P. carinii-specific hi stological stains were performed on autopsy lung specimens from 534 consecu tive pediatric patients (those with AIDS and malignancies were excluded) in Santiago, Chile. P. carinii clusters were found in 4 (25%) of 16 infants w ho died of no apparent cause at arrival to the emergency department, and in 10 (2.9%) of 342 infants who died of multiple conditions at the hospital ( P = .002, Fisher's exact test). This prompted us to analyze additional seri es of infants with sudden infant death syndrome (SIDS). In 161 additional S IDS cases, 47 (35.1%) of 134 infants from Chile and 4 (14.8%) of 27 infants from Oxford, United Kingdom, were found to have P. carinii clusters in the lungs. The quantity of P. carinii cysts was small compared with the number s seen in immunocompromised hosts with P. carinii pneumonitis. This study p rovides histological evidence that primary P. carinii infection is associat ed with SIDS.