A pseudo-iliopsoas abscess.

An 88-year-old man was admitted for an examination of anemia. He had a history of gastric cancer and calcium pyrophosphate crystal deposition (CPPD) disease in the right knee that had been treated with NSAIDs. During the examination, the patient suddenly complained of pain and tenderness extending from the left lower abdomen to the inside of the thigh in association with a high fever. Other vital signs were normal. The white blood cell count was 5,140/mm and the C-reactive protein level was 17.29 mg/dL. Computed tomography detected a fluid space in the left iliopsoas muscle (Picture A, B); therefore, emergency surgical drainage of the iliopsoas cavity was performed. The contents of the cavity included CPPD crystals with inflammatory infiltrates, although no organisms were identified. The patient recovered quickly, and we ultimately diagnosed him with a pseudo-iliopsoas abscess associated with CPPD disease around the hip joint. To our knowledge, this is the second reported case of aseptic iliopsoas pyomyositis mimicking an abscess (1).