Whipple disease associated with giardiasis.

We tested 53 fixed duodenal biopsy samples from 25 patients with Whipple disease for the presence Giardia and 6 fresh duodenal biopsy samples for Giardia duodenalis DNA by polymerase chain reaction (PCR). We also used histological examination and PCR assay to determine the prevalence of G. duodenalis in duodenal biopsy samples from 150 control patients without Whipple disease. Three of 25 patients with Whipple disease had histological evidence of giardiasis, whereas only 1 of 150 control patients was affected (P<.001). By PCR, we found Giardia in 2 of 6 patients with Whipple disease whom we tested, but in only 2 of 150 control patients (P<.001). In a literature review, we identified 15 other cases of coinfection. The occurrence of these diseases may be promoted by a common immune defect or a common source of infection, or infection with one may predispose to infection with the other.