P490 Prevalence and clinical features of chronic nonbacterial osteomyelitis in a nationwide cohort of children with inflammatory bowel diseases

Abstract

Abstract Background Among musculoskeletal extraintestinal manifestations (EIM), the association between IBD and a rare autoinflammatory condition, chronic nonbacterial osteomyelitis (CNO), has been reported. The primary objective of our study was to report the clinical characteristics and the disease course of a cohort of patient with concurrent diagnosis of CNO and IBD. The secondary outcome was to define the prevalence of CNO in a nationwide cohort of patients with IBD. Methods This is a retrospective, multicenter study based on the Italian Society of Gastroenterology, Hepatology, and Pediatric Nutrition (SIGENP) IBD National Registry. The diagnosis of CNO was defined as the presence of uni- or multifocal bone inflammatory lesions with suggestive radiological or histopathological characteristics, having excluded infectious, oncological, or other inflammatory conditions. All patients under 18 years of age with a combined diagnosis of IBD and CNO identified in the registry were included. Results 18 patients with a combined diagnosis of CNO and IBD out of 4229 patients with IBD were identified, with an overall prevalence of 0.4%. 15 (83.3%) patients were male. Median age at IBD diagnosis was 10.1 years (IQR: 6.16 years), whereas median age at CNO diagnosis was 11.7 years (IQR: 6.31 years). The most frequently reported IBD phenotype was CD (13 patients, 72.2%), followed by IBD-U (3 patients, 16.7%) and UC (2 patients, 11.1%). The diagnosis of concurrent CNO was more common in patients affected by CD than in those affected by either UC or IBD-U (13/1843, 0.7% vs 5/2886, 0.2%, p=0.01). Similarly, the occurrence of CNO was more frequent in male gender when compared to female one (15/2312, 0.6% vs 3/1917, 0.1%, p=0.01). All the patients had multifocal bone involvement; 2 (11.1%) developed subsequently dermatological manifestations consistent with SAPHO syndrome. In 8 patients (44.4%) IBD onset preceded CNO diagnosis, in 6 (33.3%) IBD onset followed CNO diagnosis, whereas in the remaining 4 patients (22.2%) the diagnosis of IBD and CNO was concomitant. Table 1. summarizes therapeutic approach to both conditions in each of the patient identified in our case series. At the end of follow-up, 14 (77.8%) patients had achieved IBD clinical and biochemical remission. Ten (55.6%) patients achieved clinical and radiological remission of bone lesions, 6 (32.3%) had achieved clinical remission but showed persistence of bone lesions at magnetic resonance imaging (MRI), 2 (11.1%) had persistence of both clinical and radiological activity. Conclusion Our findings support the hypothesis that CNO disease spectrum can be considered a rare extraintestinal manifestation of IBD, with a low but still non-negligible prevalence.