Pyomyositis of the Piriformis Muscle Secondary to Cellulitis Complicating Lymphedema.

A woman in her 70s with a 20-year history of postoperative edema and repeated cellulitis after surgery and chemotherapy for ovarian cancer presented with pain, redness, and swelling in her left lower leg. She was admitted with dehydration, disorientation, and elevated inflammation. After antibiotic treatment, redness of the lower extremities gradually improved. However, the patient complained of severe back pain after 10 days of treatment. Computed tomography (CT) revealed an abscess of the right pisiform muscle and patient was diagnosed with pyomyositis of the piriformis muscle. On hospital day 18, CT-guided percutaneous drainage of the abscess was performed. At the 6-month follow-up, there was no recurrence of the abscess. It is difficult to diagnose pyomyositis of the piriformis muscle via physical examination. This extremely rare case involves pyomyositis of the piriformis muscle as a result of cellulitis due to lymphedema. If antibiotic treatment for cellulitis in a patient with lymphedema is unsuccessful and severe pain persists, early imaging diagnosis should be considered.