Malignant Psoas Syndrome

The patient in this case presented with a malignant psoas syndrome secondary to a primary psoas muscle sarcoma. A malignant psoas syndrome is characterized by the presence of lumbar plexopathy, ipsilateral hip flexion, and severe pain with attempted hip extension. The presence of severe, atraumatic joint pain with fevers and other associated systemic symptoms should raise the clinical index of suspicion for a diagnosis requiring urgent attention including infection and malignancy.