A 64-year-old man with prostate cancer and bone metastasis admitted for nausea, left abdominal pain showed no abnormal, and fever, abdominal ultrasound or chest X-ray findings. Despite antibiotics, left abdominal pain persisted for several days. Abdominal computed tomography (CT), showed splenic infarction. Transesophageal echocardiography suggested infectious endocarditis (IE) as a possible infarction cause, and roth spots were found on the retina. Gemella morbillorum was detected from blood culture. IE commonly causes Fever of Unknown Origin found by infarction. G. morbillorum, an anaerobic grampositive, viridans group streptococci, is indigenous to the oropharynx, upper respiratory, urogenital, and gastrointestinal tracts, and is thought to have weak toxity and pathogenicity in the body.
