650 - Chronic Nonbacterial Osteomyelitis - A Pediatrician’s Guide to Diagnosis and Management

Publication Number: 650.4454

Aarat M. Patel, University of Virginia School of Medicine, Glen Allen, VA, United States; Sophie Henning, UVA Childrens, Charlottesville, VA, United States; Kelley Lee, Bon Secours Mercy Health, Glen Allen, VA, United States

Background: CNO is an aseptic autoinflammatory bone disease of unknown etiology with signs/symptoms of bone pain, possible swelling, tenderness and/or warmth over the affected area, fever, and rash. Diagnosis can be delayed due to the non-specific nature of symptoms, referral patterns to non-rheumatology specialists, and normal imaging studies. The goal of treatment is the resolution of bone pain and swelling.

Objective: To evaluate the clinical, laboratory, and imaging characteristics that can lead to a diagnosis in children. To describe effective treatments that pediatricians can start before referral to rheumatology.

Design/Methods: This is a retrospective case-series of patients diagnosed with CNO (n=46). They were diagnosed and managed clinically in usual care between 2012 and 2024 in Richmond and Charlottesville, Virginia. The clinical manifestations, laboratory results, and imaging studies that lead to a diagnosis of CNO were reviewed. Diagnosis was confirmed using the newly proposed ACR/EULAR classification criteria and other diagnostic criteria (see figure 1). Subsequently treatment response was reviewed.

Results: Diagnosis averaged at age 10 (range 2-17), with symptoms to diagnosis time averaging 23 months (range 1-120). Bone pain (100%) and arthritis (56%) were most common, with fever (26%) and rash (7%) less so. Elevated ESR and CRP levels were found in 65% of Rheumatology initial visits. The new classification criteria was met by 97%. Those that did not fulfill this criteria did fulfill other diagnostic criteria (Bristol and Jansson). Radiographic abnormalities leading to CNO diagnosis was found with regional MRI (70%), bone scan (43%) with some requiring full body MRI (28%). Conventional X-ray only identified 37% of patients. Patients often underwent multiple imaging studies (MRI, bone scan, x-ray, CT scan). Treatment history can be seen in the figure.

Conclusion(s): The analysis of CNO highlights key findings for pediatricians. Time to diagnosis varies due to early identification challenges, with many patients lacking abnormal lab or X-ray results. NSAIDs were effective for 24% of cases, offering a simple initial treatment option. Advanced imaging, including full body or regional MRI, is often essential for a definitive diagnosis. The newly proposed ACR/EULAR classification criteria simplify facilitating a diagnosis, reducing the need for bone biopsy or advanced imaging studies.