Pyogenic Sacroiliitis in a Pediatric Patient: A Rare Case of Infection by Streptococcus intermedius.

This is a case report of pyogenic sacroiliitis in a pediatric patient caused by Streptococcus intermedius. The patient is a 16-year-old boy who presented to an emergency department with sudden onset of back pain radiating to the left lower extremity. The diagnosis was confounded by the presence of isthmic spondylolisthesis. Plain radiography demonstrated mild isthmic spondylolisthesis but no radiographic signs of tumor, trauma, infection, arthritis, or other developmental problems. The C-reactive protein level was 23 mg/L. Over the next 24 hours, the patient developed fever, and the C-reactive protein level increased to 233 mg/L. Sacroiliitis and an iliopsoas abscess were identified on MRI. Blood cultures grew S intermedius. The patient responded to antibiotic treatment and needle aspiration under CT guidance. Sacroiliitis is an uncommon condition and, to our knowledge, there is only one other case report of its being caused by S intermedius. The previous report was in an adult.