Chronic nonbacterial osteomyelitis and inflammatory bowel disease in children: A French national cohort

OBJECTIVES: Inflammatory bowel disease (IBD) and chronic nonbacterial osteomyelitis (CNO) is a rare association. Its prevalence is probably underestimated due to low awareness among clinicians. The aim of this study was to describe the French pediatric national cohort and to estimate the incidence of CNO among IBD. METHODS: We retrospectively collected all reports of IBD-CNO association from pediatric gastroenterological and rheumatologic units between 2000 and 2024. We analyzed demographic data; age of the onset; IBD type; CNO localizations; dermatological lesions; explorations results; medications; follow-up. Incidence was estimated using French regional inception population-based cohort EPIMAD data. RESULTS: Thirty-seven patients were identified. Median age at the onset was 13.5 years (interquartile range [IQR] 11.5-14.5). CNO diagnosis preceded IBD in 11 cases, followed it in 13 cases, while 13 IBD-CNO cases were diagnosed simultaneously (median interval 1 year). IBD included 25 Crohn's disease, 10 ulcerative colitis, 2 IBD-unclassified. Bone localizations predominated in lower limbs and pelvis (75.3%). Fourteen children (37.8%) had dermatological lesions. At last follow-up (median 3 years, IQR 1.25-4.75), 28 patients (75.7%) were in IBD-CNO remission, having mostly anti-tumor necrosis factor (TNF)-α (p = 0.041, 82.1% remission, 44.4% relapse) in monotherapy (60.7%). We estimate the incidence of this association among French pediatric IBD at 1 case for 20,000 patients-year. CONCLUSION: This study describes a large national cohort of pediatric IBD-CNO association. Gastroenterologist should request a whole body-magnetic resonance imaging when IBD patients present chronic bone pain. Multidisciplinary management involving rheumatologists and dermatologists is recommended. Most patients responded to anti-TNF-α antibodies, which could avoid bone complications.