Image: PD

1. 84% of infants with unexplained death were colonized with Pneumocystis, versus 66% of infants whose deaths were explained.

2. Pneumocystis colonization was associated with increased mucus production.

3. These results support a model for the etiology of Sudden Unexpected Infant Death involving Pneumocystis colonization and increased mucus production subsequently leading to an infant’s death.

The results from this study suggest a correlation in Pneumocystis colonization and unexplained infant death. This is the first study to show that Pneumocystis appears highly prevalent in infants and is correlated with upregulation of mucus in the airway. The authors theorize that Pneumocystis colonization causes an upregulation of mucus production which subsequently causes a narrowing of the airway and eventually infant death. This study did not examine for the presence of other pathogens, and the nature of the study did not allow it to correlate findings with healthy living controls. Future studies comparing colonization rates and examining for additional pathogens should be performed to further elucidate this correlation.

Click to read the study in CID

Click to read an accompanying editorial in CID

Study author, Dr. Sergio Vargas, MD, talks to 2 Minute Medicine: University of Chile School of Medicine

“The primary infection by Pneumocystis in presumably-normal infants is largely unrecognized. This infection is regarded as innocuous under the current view of Pneumocystis as a pathogen restricted to the immunocompromised host. We found Pneumocystis in over 90% of infants between 2 and 5 months of age dying suddenly and unexpectedly in the community. Furthermore, Pneumocystis associated to increased mucus a well-recognized by-product of innate immunity suggesting pathogenic expression may depend on ability to clear mucus.”

Background reading:

1. CDC: Sudden Unexpected Infant Death and Sudden Infant Death Syndrome

2. CDC: Pneumocystis Pneumonia

3. Search for Primary Infections by Pneumocystis carinii in a Cohort of Normal, Healthy Infants

In Depth [autopsy study]: examined lung tissue of deceased infants in Chile. 128 lung tissue specimens were collected for infants between the ages of 3 days and 12 months who died unexpectedly between 1999 and 2004. 84% of infants with unexplained death after autopsy were colonized with Pneumocystis while only 67% of infants whose deaths were explained were colonized. When stratified by age, 3- and 4-month old infants with unexplained death had colonization rates of 97% and 100% respectively. Additionally, Pneumocystis colonization was associated with increased mucus production.

By [AS] and [MS]

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