Treatment responses and relapse predictors in pediatric CNO: insights from a referral center.

Abstract

To evaluate the clinical features and diagnostic work-up of patients with Chronic Nonbacterial Osteomyelitis (CNO) followed at a tertiary referral center, and to contribute real-life data to the existing literature. We also aimed to compare our treatment approach to the EULAR recommendations for CNO. This retrospective cohort study included 80 patients diagnosed with CNO between 2020 and 2025, based on EULAR/ACR classification criteria. Demographic, clinical, laboratory, imaging, and treatment data were collected from electronic medical records. Patients were analyzed according to relapse status, treatment response, and MRI findings. The mean age at symptom onset was 9.4 ± 4.2 years, with a diagnostic delay of 2.2 ± 2.4 years. The most common symptoms were bone pain and fatigue, and 27.5% had skin involvement. Only five patients responded to NSAID monotherapy. DMARDs were used in 68 patients, but only 11 achieved clinical remission. Anti-TNF therapy was the most frequently used treatment modality. In multivariate analysis, the number of bones involved was significantly associated with relapse (OR: 1.20, 95% CI: 1.03-1.39, p= 0.017). Biologics such as secukinumab, anakinra, canakinumab, and tocilizumab were used in refractory cases with favorable responses. Pamidronate was administered to 20 patients; while 3 achieved complete remission, the remaining patients experienced rapid pain relief but ultimately required anti-TNF therapy. Conventional DMARDs are effective in a limited subset of CNO patients, who may represent a milder disease phenotype. The presence of skin involvement and a greater number of affected bones may both suggest a more aggressive disease course. Anti-TNF therapies are the most effective agents, while other biologics offer promising results in resistant cases. Prospective studies are needed to guide individualized treatment strategies.