Background: Chronic nonbacterial osteomyelitis (CNO) is a rare auto-inflammatory bone disease. CNO, especially the adult variant, lacks guidelines, resulting in an ambiguous clinical definition and extreme treatment diversity worldwide. We mapped current diagnostic and therapeutic practices in CNO, as groundwork for a consensus clinical guideline
Methods: A primary survey was spread among rheumatological/bone networks and 57 CNO experts as identified from literature (May 2022), covering terminology, diagnostic tools (clinical, radiological, biochemical) and treatment steps. A secondary survey (sent to primary survey responders in August 2022) further queried candidate diagnostic criteria, treatment motivations, disease activity and treatment response monitoring.
Results: 36 and 23 physicians completed the primary and secondary survey respectively. Diagnosis was mainly based on individual physician assessment rather than proposed diagnostic criteria. The relevance of clinical features was assessed differentially between physicians, exempting the agreed importance of relapse-remitting bone pain. MRI was most frequently performed as imaging diagnostic, and also preferred for its utility by 47%. X-rays were second-most frequently used, while considered least informative. Typical imaging features reported were hyperostosis, osteitis, osteosclerosis, bone marrow edema, while degeneration, soft tissue calcification, and ankylosis were not regarded indicative. Inflammation markers and bone markers were generally regarded unhelpful in diagnosing, and monitoring adult CNO. Physicians infrequently performed bone biopsies nor regarded them a key diagnostic. After a first-line treatment of non-steroidal anti-inflammatory drugs/COX-2 inhibitors (installed by 83%), pamidronate, methotrexate, and TNF-a-inhibition (TNFi) were the most frequent second/third-line therapeutics, the latter two regarded especially convenient to co-target extra-skeletal inflammation as often seen in adult CNO.  Pamidronate and TNFi and wer