Background/Purpose: Chronic nonbacterial osteomyelitis (CNO) is associated with various comorbidities and long-term complications. The CHronic nonbacterial Osteomyelitis International Registry (CHOIR) is a multi-national database that allows researchers to determine the prevalence of long-term risks, growth outcomes, and medication use and related adverse effects over time in children with CNO.

Methods: Children with CNO enrolled in CHOIR across 17 global sites between August 1, 2018 to December 31, 2024. Demographic and disease-related data were collected at baseline and follow-up visits. Data were summarized via descriptive statistics.

Results: A total of 585 children with CNO were included with a median age of 9.5 years at disease onset (Table 1). Of these, 171 had follow-up for greater than 5 years. Whole body (WB) MRIs were done in 469 patients at least once, and 233 at diagnosis. Rate of active spinal lesions confirmed by MRI decreased from 12% at diagnosis to 2% at 5 years. At baseline, height, weight, and body mass index (BMI) were within normal ranges and persisted over 5 years (Table 2). Of 459 patients with a total of 1,649 patient-years of follow-up and complete data on comorbidities and adverse events, the mean follow-up was 3.6 years since diagnosis. Prior to diagnosis of CNO, the most common comorbidities were inflammatory bowel disease (IBD) (32), inflammatory arthritis (27), and psoriasis (26). After diagnosis, new autoimmune conditions that developed were psoriasis (37), arthritis (18), IBD (5), and less commonly (< 5) pustulosis, hidradenitis, celiac disease, and type 1 diabetes (Table 3). Amplified pain syndrome occurred in 13 patients at baseline and 15 more during follow-up. Vertebral compression fractures occurred in 25 patients initially and 6 more during follow-up. Seven had vertebral plana prior to diagnosis of CNO. Additionally, 12 patients prior to and 17 more after diagnosis experienced fractures at non-lesion sites related to trauma. Of these, 81% of vertebral and 41% of non-vertebral fractures occurred before diagnosis. The most common vertebral and non-vertebral fracture sites were the thoracic spine (81%) and hand (26%) (Table 3). During follow-up, 333 patients received second-line treatments with one or more conventional synthetic disease-modifying anti-rheumatic drugs (csDMARDs), tumor necrosis factor inhibitors (TNFi), bisphosphonates, or JAK inhibitors. Twenty-four (65%) of 37 patients who developed psoriasis after diagnosis were exposed to csDMARDs and/or TNFi at a mean of 2 years post-diagnosis. Additionally, four of five patients requiring intravenous antibiotics for infection were treated with TNFi within 60 days.

Conclusion: We were able to leverage CHOIR to estimate the frequency of various comorbidities, long-term risks, and growth impacts on children with CNO. Over 5-years of follow-up, the number of active spinal lesions on MRI decreased and fewer compression fractures occurred after diagnosis compared to before diagnosis. Growth metrics remained within normal range at the population level. The most common medical events after diagnosis of CNO were psoriasis and inflammatory arthritis.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/prevalence-of-risks-and-complications-in-a-longitudinal-international-cohort-of-children-with-chronic-nonbacterial-osteomyelitis-cno/