Dientamoeba fragilis: a gastrointestinal protozoan infection in adults.

Dientamoeba fragilis is a protozoan parasite of the large intestine of man. Individuals with infection may be asymptomatic or have gastrointestinal and systemic symptoms. We report a patient with symptomatic D. fragilis infection and negative extensive laboratory and radiological workup, with resolution of symptoms after diiodohydroxyquin therapy. No parasites were detected in three follow-up stool examinations. We then undertook retrospective study to define and describe further clinical symptoms in adults with this infection by analysis of data from medical records of 50 subjects with this parasite.