BACKGROUND
Helicobacter cinaedi is a rare bacterium, accounting for only 0.2% of the positive isolates in blood cultures. Previous reports note that patients with H. cinaedi infection often have underlying diseases. H. cinaedi infection is diagnosed by blood culture. However, because of the slow growth of this bacterium in blood culture, the diagnosis can be missed.
CASE REPORT
A 78-year-old man gradually developed erythema and pain in his left arm, then left shoulder and both lower legs. The patient presented to our hospital on day 17. He was afebrile, but the examination was remarkable for tenderness in both gastrocnemius muscles and erythema from the distal left lower leg to the ankle. We suspected pyomyositis and cellulitis and started oral administration of amoxicillin-clavulanate. On day 22, H. cinaedi was detected in blood cultures. Based on these findings, we diagnosed pyogenic myositis and cellulitis caused by H. cinaedi bacteremia. On day 24, antibiotic therapy was changed to intravenous ampicillin, and symptoms improved. Additional examination did not reveal any underlying immunodeficiency disorder, such as malignancy or HIV infection.
CONCLUSIONS
H. cinaedi infection can occur in healthy patients. Myalgia can be caused by pyogenic myositis because of bacteremia. In cases of myalgia or cellulitis of unknown etiology, blood cultures can be useful when bacteremia is suspected; blood samples should be monitored over an extended period.

Keywords: Bacteremia; Blood Culture; Helicobacter cinaedi; Myalgia