Abstract
Pyomyositis has recently been recognized as a primary infection of the large skeletal muscles, and it is often accompanied by single or multiple intramuscular abscess formation. Immunocompromised patients, including those with diabetes mellitus, human immunodeficiency virus infection, and cancer, as well as those undergoing chemotherapy, are at a greater risk of developing pyomyositis. A 78-year-old Japanese man with recurrent gastric cancer being treated with chemotherapy presented with sudden-onset pain in his left lower extremity while undergoing a second-line regimen with irinotecan. T2-weighted magnetic resonance imaging (MRI) showed an abnormally high-intensity signal in the left internal and external obturator muscles, a finding consistent with pyomyositis. Following intensive antibiotic treatment, the patient recovered completely and was able to resume chemotherapy with irinotecan. For a patient who developed pyomyositis during chemotherapy for gastric cancer, early diagnosis using MRI followed by administration of timely intensive antibiotic therapy resulted in complete recovery.