E007 Treatment of paediatric chronic nonbacterial osteomyelitis (CNO): a systematic review of the literature

Abstract Background/Aims Chronic nonbacterial osteomyelitis (CNO) is a rare autoinflammatory bone disease that mainly affects children and young people. It usually presents with bone pain and may result in hyperostosis and/or sometimes fractures. While the underlying pathophysiology isn’t fully understood, it involves the activation of the NLRP3 inflammasomes and an imbalance between pro- and anti-inflammatory cytokines. Treatment is empiric and based on experience and/or published case reports and case series rather than formal evidence. Methods For this project, a systematic review of the literature was carried out using PRISMA guidelines. Searches were completed using Medline, Embase, PubMed, the Cochrane Library, ClinicalTrials.gov, and the WHO ICTRP. A total of 1,376 records were identified. After removing duplicates, studies underwent title and abstract screening (N = 805) and full-text review (N = 112); 54 studies were included in this study. No randomised controlled trials (RCTs) were identified. Instead, 31 cohort studies and 22 case series studies were reviewed, resulting in an overall low evidence level (between 2, cohort studies, and 4, case series). Sample sizes of individual studies ranged between 4 and 774 patients. Results Several treatment options have been used and are effective to treat CNO; none of them are licensed for use in this disease. Nonsteroidal anti-inflammatory drugs (NSAIDs) are most frequently used as first-line treatment. They provide pain relief and can induce remission in the first 12 months, although relapses are common. Conventional disease-modifying antirheumatic drugs (DMARDs) have shown mixed results but can be beneficial, especially in patients who also have arthritis, skin inflammation, or inflammatory bowel disease. Biologic DMARDs, particularly TNF inhibitors, are effective for both bone and extra-skeletal disease in most patients. Bisphosphonates are associated with quick improvement of symptoms and may induce long-lasting remission, but, based on a recent international cohort study, relapses may occur more often compared with TNF inhibitors. Conclusion Interpretation of reports in the literature is difficult because of the relatively small number of studies available, variable diagnostic and/or inclusion criteria applied, and inconsistent (usually descriptive) outcomes reported. Among treatments used in CNO, TNF inhibitors and bisphosphonates are associated with the highest remission rates. Vertebral involvement with structural damage requires bisphosphonate treatment to induce rapid remission. Prospective, randomised studies are needed to improve the evidence base and support the development of clearer treatment guidelines for CNO. Disclosure S. Turner: None. E. Roberts: None. C. Hedrich: None.