Pyomyositis of the iliacus muscle complicated with septic sacroiliitis.

We report a rare case of pyomyositis of the iliacus muscle in a 29-year-old woman. After 2 weeks of adequate treatment, secondary septic sacroiliitis occurred, a complication that had not been described previously. Pyomyositis of the iliacus muscle must be considered in the differential diagnosis of acute pain in the hip region.