An international team of pediatric rheumatology experts has developed and validated the first classification criteria for pediatric chronic nonbacterial osteomyelitis, a rare autoinflammatory bone disease.
The initiative, led by the European Alliance of Associations for Rheumatology (EULAR) and the American College of Rheumatology (ACR), involved 31 centers across six continents. The effort incorporated international expert consensus, data-driven methods, and the patient’s perspective.
Chronic nonbacterial osteomyelitis (CNO) affects children and adolescents, causing chronic bone inflammation that leads to pain, swelling, and potential long-term complications such as deformity or disability. Diagnosis is difficult due to gradual onset, variable symptoms, and clinical overlap with other conditions. Until now, no standardized classification criteria existed for research or clinical trials.
The classification criteria were developed through a four-phase process. Pediatric rheumatologists first identified relevant disease features via survey. These were refined and weighted using structured decision-making. The criteria were tested in a development cohort of 441 patients and validated in a separate cohort of 514 children worldwide.
To be classified as having CNO, a child must be under 18 years of age and experience bone pain or musculoskeletal limitations lasting at least six weeks. Imaging must show abnormal bone findings, such as inflammation visible on radiography or MRI. Malignancy, infection, vitamin C deficiency, and hypophosphatasia must be excluded.
If these conditions are met, a score is calculated based on nine features—five clinical and four laboratory or pathology-related. A minimum of 55 points is required to meet the classification threshold. The criteria can be applied without the absolute requirement for a bone biopsy.
The criteria demonstrated a sensitivity of 82% and a specificity of 98% in validation testing, indicating strong performance in distinguishing true cases from other conditions.
“Ultimately, this validated classification criteria provides a crucial foundation for our future clinical trials aimed at developing new treatments and improving outcomes for patients,” said Professor Yongdong Zhao, Director of the Clinical CNO Program at Seattle Children’s Hospital and the University of Washington School of Medicine.
The new framework provides a standardized tool for researchers and clinicians enrolling patients in studies. Previously, the absence of standardized criteria limited trial recruitment and hindered cross-study comparisons.
By offering a validated and consistent approach, the criteria are expected to facilitate improved recognition of CNO, enable better characterization of its natural history, and support the development of targeted therapies.
Source: EULAR press release