Mandibular involvement in pediatric chronic nonbacterial osteomyelitis: a retrospective study of 12 patients from a single-center.

INTRODUCTION: The quantitative imaging assessment and comparative effectiveness of second-line treatments for chronic nonbacterial osteomyelitis (CNO) remain inconclusive. Our study aimed to analyze the clinical characteristics and effectiveness of second-line medications in CNO children with mandibular involvement and to evaluate the applicability of the mRINBO (Modified Radiographic Index of Nonbacterial Osteomyelitis) scoring tool. METHODS: We conducted a retrospective study of 12 CNO patients who visited Peking Union Medical College Hospital between April 2016 and August 2023. The study included demographic characteristics, clinical manifestations, inflammatory markers, imaging data, and treatment effectiveness. Imaging data were compared using the mRINBO score. RESULTS: Seventy-five percent of the patients had unilateral mandibular involvement, and 33.33% maintained a single lesion throughout the follow-up period. Following second-line treatment, the average mRINBO score decreased from 5.36 +/- 1.03 to 4.4 +/- 1.43 points (P = 0.023). Clinical symptom scores decreased from a median of 1 (0.875-1) to 0.5 (0-0.5) points (P = 0.023), concurrently. At 9 months of follow-up, the clinical remission rates were 75% for the TNF inhibitors group, and 100% for the bisphosphonate group (P > 0.05). CONCLUSION: CNO affecting the mandible predominantly involves unilateral involvement, with some children maintaining single-site involvement throughout the course of the disease. The mRINBO scoring tool demonstrates applicability in assessing radiographic changes during follow-up of CNO patients. Second-line treatments show better effectiveness with TNF inhibitors and bisphosphonates, although a comparison of the effectiveness between them needs further investigation. Key Points * CNO affecting the mandible typically involves one side, and some children may exhibit only a single site of involvement. * The mRINBO score tool demonstrates applicability in assessing imaging changes in CNO patients, and baseline scores may be more sensitive than inflammatory markers in reflecting disease activity. * TNF inhibitors and bisphosphonates have shown better effectiveness in treatments for CNO.