Severe Blastocystis hominis in an elderly man.

We describe a unique case of severe Blastocystis hominis infection in an elderly man with severe dehydration, marked leukocytosis and hypoalbuminaemia after antibiotic treatment for right pneumonia. The patient recovered after treatment with metronidazole. This case presentation demonstrates the ability of B. hominis to induce severe gastrointestinal manifestations and general deterioration, particularly in light of the controversy surrounding its possible potential pathogenicity. We believe, therefore that aggressive treatment with metronidazole should be instituted, following demonstration of the parasite in the stools, if diarrhoea is protracted, since it may well be attributed to Blastocystis infection.