Diagnosis, treatment and monitoring of chronic nonbacterial osteomyelitis (CNO) and chronic recurrent multifocal osteomyelitis (CRMO) – Evidence, practice and consensus-based recommendations from the German pediatric rheumatology society (GKJR)

Chronic nonbacterial osteomyelitis (CNO), sometimes also referred to as chronic recurrent multifocal osteomyelitis (CRMO), is a rare autoinflammatory bone disease primarily affecting children and adolescents. In the absence of diagnostic criteria and biomarkers, CNO remains a diagnosis of exclusion, and treatment is largely empiric. This initiative of the German Society of Pediatric and Adolescent Rheumatology (GKJR) aimed to develop evidence-, practice-, and consensus-based recommendations for the diagnosis and management of CNO, incorporating current knowledge on pathophysiology, therapeutic strategies and disease monitoring. Based on a systematic literature review and a subsequent Delphi survey, preliminary statements were developed. This was followed by expert group voting exercises (nominal group exercise) to agree final statements and recommendations. Statements and recommendations were developed for the diagnosis, treatment and disease monitoring of CNO in a multidisciplinary expert group, involving patients/families. Where available, diagnostic workup should include whole-body skeletal imaging (usually MRI). Treatment options include first-line (NSAIDs, short-term corticosteroids) and second-line (conventional and/or biologic DMARDs, bisphosphonates) agents. In patients with vertebral involvement, rapid treatment with bisphosphonates and/or TNF inhibitors is recommended. As CNO is a chronic disease, long-term monitoring is recommended, including follow-up after treatment discontinuation. Although evidence levels are low to moderate, consensus statements and recommendations provide structured guidance for clinicians diagnosing and treating CNO. They provide a framework for harmonized care aiming at improved long-term outcomes. • CNO is a rare autoinflammatory bone disease in children and adolescents that remains a diagnosis of exclusion. Diagnosis and treatment strategies lack evidence, and, consequently, clinical practice varies widely. • Evidence- and consensus-based recommendations provide a structured diagnostic algorithm. Stepwise treatment strategies are proposed, including defined targets, follow-up intervals and exit strategies. • Recommendations promote multidisciplinary and harmonized care plans for pediatric CNO to reach targets agreed with patients/families. They establish a framework for prospective studies and validation of outcome measures.