E1193. Chronic Recurrent Multifocal Osteomyelitis: A Challenging Diagnosis
  1. Anastacia Wahl; Georgetown University School of Medicine
  2. Ian Amber; MedStar Georgetown University Hospital
  3. Arash Zandieh; MedStar Georgetown University Hospital
Chronic recurrent multifocal osteomyelitis (CRMO) is an inflammatory bone disorder afflicting children and adolescents without infectious cause. The diagnosis is made by clinical exclusion, and imaging plays a key role in lesion characterization and surveillance. In this educational exhibit, we will review the clinical work-up and relevant diagnostic imaging features of CRMO using an illustrative, case-based approach with radiologic-pathologic correlation.

Educational Goals / Teaching Points
CRMO is a challenging diagnosis that may be encountered in young patients with single or multifocal sites of osteitis and inflammatory bone disease. The diagnosis is established by clinical parameters, imaging, and histopathology. Common sites of involvement include the tibia (among other sites in the lower extremity), pelvis, and medial clavicle. Bone scans and MRI may serve as useful tools for multi-site involvement. Active disease can mimic acute infectious osteomyelitis or aggressive malignancy, while the reparative phase can mimic chronic infectious osteomyelitis or nonaggressive neoplastic processes.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
CRMO presents with nonspecific clinical features of pain and swelling, with symptoms that can wax and wane over months. Blood cultures are typically negative, and bone biopsy yields no infectious cause. Plain-film radiography can be negative, but may demonstrate a lytic lesion within the metaphysis or adjacent to the physis. In the late/chronic phase, radiographs may reveal progressive sclerosis or hyperostosis. Recurrence may demonstrate new lytic areas or periosteal reaction. Magnetic resonance imaging (MRI) plays a key role in lesion characterization and should be performed with wide field-of-view or using whole-body imaging techniques. CRMO lesions demonstrate patchy low signal intensity on T1-weighted images, hyperintense T2-weighted signal abnormality, and enhancement, periostitis, and adjacent soft tissue edema. Transphyseal edema may be seen. The lack of sequestration, fistula, or abscess formation is key in the MRI workup. Establishing multifocal disease is also important. Primary diagnostic criteria include a lack of causative organism, characteristic prolonged/fluctuating clinical course, and typical or multifocal sites of disease, including asymptomatic sites that may be discovered on surveillance MRI. Common sites of disease include the distal tibia, pelvis, medial clavicle, and ribs. The differential diagnosis includes infectious osteomyelitis, Langerhans cell histiocytosis, leukemia, and primary bone malignancies such as Ewing sarcoma or lymphoma.

CRMO is a difficult diagnosis. An awareness of the clinical findings, diagnostic work-up, and relevant imaging findings will help clinicians and radiologists manage this rare and challenging condition.