Clinical characteristics and outcomes of chronic nonbacterial osteomyelitis/chronic recurrent multifocal osteomyelitis in Korean children and adolescents: a single-center retrospective study

Objective: Chronic nonbacterial osteomyelitis (CNO)/chronic recurrent multifocal osteomyelitis (CRMO) is a rare autoinflammatory bone disorder primarily affecting children, with limited data in Asian populations.This study describes the clinical features, treatment patterns, and prognosis of CNO/CRMO in Korean pediatric patients.Methods: We retrospectively reviewed the medical records of 56 patients aged <19 years diagnosed with CNO/CRMO at our hospital between 2004 and 2022.Diagnosis relied on characteristic clinical and radiological findings or sterile histology, with infection and malignancy excluded.Primary endpoints were clinical and radiological remission as well as relapse; secondary endpoints encompassed height changes, complications, and mortality.Results: Of 56 patients, 64.3% were male.Mean age at diagnosis was 11.4±3.3years, with a follow-up of 2.2±2.9 years.Diagnostic delay averaged 14.2±17.5 months.The knee was the most commonly affected site (57.1%), with a mean of 2.0±1.2sites involved per patient.Elevated initial inflammatory marker levels were observed (erythrocyte sedimentation rate 31.2±29.1 mm/h, C-reactive protein 2.0±4.8mg/dL).Treatments included non-steroidal anti-inflammatory drugs (89.3%), disease-modifying antirheumatic drugs (48.2%), steroids (48.2%), bisphosphonates (n=1), and biologics (n=7).Clinical remission was achieved in 39.3%, radiological remission in 30.4%, and laboratory improvement in 41.1%.Complications occurred in 16.1%, including two surgeries.Reduced final height percentiles were observed in 33.3%; younger age at diagnosis predicted better treatment response (10.6±3.5 vs. 12.5±2.8years).Conclusion: This Korean pediatric CNO/CRMO study shows male predominance, infrequent clavicular involvement, and frequent steroid use, differing from Western reports.Early diagnosis and individualized treatments are crucial for preventing complications and improving long-term outcomes.