Pathology of Dientamoeba Fragilis Infections of the Appendix

Robert B. BurrowsSixth Army Area Medical Laboratory, Fort Baker, California

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Martin A. SwerdlowSixth Army Area Medical Laboratory, Fort Baker, California

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John K. FrostSixth Army Area Medical Laboratory, Fort Baker, California

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Claude K. LeeperSixth Army Area Medical Laboratory, Fort Baker, California

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Summary and Conclusions

Dientamoeba fragilis has been encountered in four appendices and in each case some of the amebae were seen with ingested blood cells. No actual invasion of tissue was found in any case. A marked fibrosis, which could be caused by a low grade irritant, was present in the wall of each appendix. Three of the four appendices also contained worm ova, larvae or adults, but the fibrosis could not be attributed to these. Dientamoeba appears as the most likely cause of this fibrosis.

Inasmuch as various symptoms have been reported in D. fragilis infections; as these symptoms generally disappear when the parasite is eliminated; as these amebae are shown to ingest blood cells; and as it apparently acts as an irritant and causes a localized tissue reaction, such as fibrosis, this species probably should be considered as a pathogenic species, but with a lower order of pathogenicity than that produced by Endamoeba histolytica or Balantidium coli.

Author Notes

Present address: School of Medicine, University of California, San Francisco, Calif.

Present address: Department of Pathology, School of Medicine, University of Missouri, Columbia, Mo.

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