A Case Report of Infectious Sacroiliitis in an Adult Presenting to the Emergency Department with Inability to Walk.

BACKGROUND: Infectious sacroiliitis (ISI) is an uncommon cause of back and hip pain in which the sacroiliac joint, either unilateral or bilateral, is inflamed from an infectious source. Historically, this has been an easily missed diagnosis due to nonspecific presenting symptoms along with subtle nondistinguishable laboratory abnormalities. CASE REPORT: We describe an injection drug user presenting with right-sided ISI who presented with hip and back pain and inability to walk. The patient had tenderness over his right sacroiliac joint, and despite negative plain radiographs, a magnetic resonance imaging (MRI) scan was obtained from the Emergency Department (ED) given the patient's risk factors for infection. Concerning findings of ISI on this MRI led to a computed tomography-guided biopsy during the patient's hospital admission, which revealed alpha-hemolytic Streptococcus as the responsible pathogen. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Infectious sacroiliitis is a rare condition that is difficult to diagnose, and carries increasing morbidity when diagnosis is delayed. We aim to increase awareness through a case report of a patient encountered in the ED.