A 44-year-old male patient was admitted with dizziness and diarrhea

presenting with a 10-year history of hypertension. Routine fecal examination indicated a negative occult blood test and 0-1 red blood cells per high-power field (RBCs/HP). Based on the medical history and morphological re-examination

the clinical diagnoses were cerebral infarction and Blastocystis hominisinfection. The patient received oral metronidazole (400 mg three times daily) combined with probiotics to modulate the intestinal flora. After 7 days of treatment

diarrhea symptoms alleviated

and follow-up fecal routine examination revealed no parasites. Blastocystis hominisis a common intestinal protozoan characterized by pleomorphic morphology

frequently causing diagnostic confusion with RBCs

fat droplets

and Giardia lamblia. This case report summarizes the microscopic features of vacuolar-form Blastocystis hoministo enhance the identification capability of laboratory personnel

thereby reducing misdiagnosis and providing reliable evidence for clinical diagnosis and treatment.