Dientamoeba Fragilis, an Intestinal Pathogen

In a previous paper1a detailed report was made on the pathology of four cases of Dientamoeba fragilis infection of the appendix. Since then 11 additional cases have been encountered, some in a review of cases back to January, 1951, and some in recent appendixes submitted to this laboratory. In this paper additional evidence tending to incriminate Dientamoeba as a pathogen is presented. For many years there has been some question of the possible pathogenicity of Dientamoeba, as patients infected with this species exhibited symptoms which did not disappear until treatment eliminated the infection. These reports were summarized in the previous paper1; however, no concrete evidence of pathogenicity existed until the work on D. fragilis in the appendix demonstrated that the amebas ingest red blood cells and that fibrosis of the appendiceal wall could be demonstrated in each case. In an examination of 1,130 appendixes, D. fragilis has