Unmasking the Parasite: When Giardiasis Looks Like Gastroenteritis.

Giardiasis is a protozoal infection that typically presents with diarrhea, abdominal pain, and malabsorption. Peripheral eosinophilia is unusual and may confound diagnosis by suggesting eosinophilic gastrointestinal disease (EGID). We present a 41-year-old woman with abdominal pain, diarrhea, malabsorption, and peripheral eosinophilia. Endoscopic biopsy performed shortly after anti-parasitic therapy demonstrated eosinophilic duodenitis, raising concern for eosinophilic gastroenteritis. However, repeat biopsy after recovery revealed resolution of eosinophilia, excluding EGID. This case highlights the importance of timing diagnostic endoscopy after giardiasis treatment to avoid misdiagnosis.