A 61-year-old woman presented to the emergency ward complaining of low back pain for a month. She had undergone several spinal surgeries and a right radical nephrectomy 30 years before. A few days earlier she was injected with an intramuscular painkiller in her right buttock. An abdominal CT scan revealed multiple abscesses in the psoas muscle and the right posterior abdominal wall, including cellulitis in the adjacent subcutaneous tissue and the injection site. A diagnosis of pyomyositis from subcutaneous dissemination was made, and intravenous cefazolin was initiated. After five days of favorable progress, treatment was switched to oral cefadroxil to complete four weeks, leading to full recovery.