Ectopic parasitism by Necator americanus in the transverse colon: a case report

Background Hookworms are soil-transmitted nematode parasites that primarily cause anemia. Although adult hookworms typically inhabit the upper small intestine, colonization of the transverse colon or rectum is exceedingly rare. The clinical symptoms of ectopic parasitism may be atypical, which can lead to misdiagnosis or missed diagnosis. We reported a case of N. americanus infection in which adult worms were identified in the transverse colon and rectum, accompanied by atypical clinical manifestations. Case summary This case report describes a 56-year-old man with hookworm infection who presented primarily with a cough and watery, unformed stools for more than one month, but without anemia. Unexplained eosinophilia raised clinical suspicion for possible parasitic infection. Multiple gastroscopies did not detect parasites in any location. Hookworm infection was confirmed by stool microscopy and identified as N. americanus by molecular analysis. Colonoscopy revealed adult hookworms in the transverse colon and rectum. Following treatment with albendazole (400 mg daily) for three consecutive days, the patient’s clinical symptoms resolved. Conclusion Ectopic parasitism often presents atypically, increasing misdiagnosis risk; heightened awareness, careful history-taking, and appropriate investigations are essential for definitive diagnosis.