Mixed intestinal protozoal infection masquerading as ulcerative colitis in advanced AIDS: a case report

Co-infection with Entamoeba histolytica (E. histolytica) and Giardia lamblia (G. lamblia) is exceptionally rare reported in individuals with human immunodeficiency virus (HIV), despite both protozoa being well-recognized etiologic agents of intestinal disease in the general population. The overlapping clinical manifestations of protozoal infections and inflammatory bowel disease may pose significant diagnostic challenges, particularly in patients with advanced immunosuppression. We report the case of a 34-year-old man with advanced acquired immunodeficiency syndrome (AIDS) who presented with persistent mucopurulent bloody stools for 2 months. Upon evaluation in our gastroenterology department, ulcerative colitis was initially considered; however, stool microscopy subsequently identified trophozoites of E. histolytica and G. lamblia. Colonoscopic assessment, supported by histopathological examination of biopsy specimens, confirmed E. histolytica infection. The patient was initiated on intravenous metronidazole in conjunction with antiretroviral therapy, leading to a gradual improvement of symptoms, with resolution of diarrhea within 10 days. This case highlights the importance of considering mixed protozoal infections in the differential diagnosis of chronic dysentery among immunocompromised patients. It further underscores the critical diagnostic value of repeated stool microscopy and histopathologic confirmation to avoid misdiagnosis and prevent delays in appropriate therapy.