Giardiasis in a hematopoietic stem cell transplant patient

Giardiasis can mimic diarrhea secondary to mucosal injury from the conditioning therapy prior to hematopoietic stem cell transplant (HSCT), as well as from graft-versus-host disease (GVHD). Herein, we describe the endoscopic diagnosis of giardiasis in a patient 2 months after HSCT for myelodysplastic syndrome. The patient was referred to gastroenterology service for suspected GVHD, but duodenal biopsy results showed Giardia lamblia. He was successfully treated with metronidazole with prompt resolution of all of his gastrointestinal symptoms. This case highlights the need to consider giardiasis in the differential diagnosis of diarrhea in the peri-transplant period.