Chronic non-bacterial osteomyelitis in children

Background: Chronic recurrent multifocal osteomyelitis (CRMO) in children is a chronic non-suppurative inflammation involving multiple sites. Some children affected by chronic non-bacterial osteomyelitis (CNO) do not have multiple lesions or a recurrent course. Objective: To characterise the long term outcome of children with the full spectrum of CNO. Methods: 30 children diagnosed with CNO were followed up for a mean of 5.6 years and their disease assessed using a clinical score, multiple imaging, and a diagnostic biopsy, including extensive microbial analysis. Results: 9 patients had unifocal non-relapsing disease, 3 unifocal lesions with relapses, 9 multifocal lesions without relapses, and 9 multifocal lesions with relapses (CRMO). Granulocytes were present significantly more often in CRMO than in unifocal and non-recurrent lesions. Pustulosis was more common in multifocal cases regardless of recurrence. Mean duration of treatment in 15 children with a single occurrence was 9.2 months. Naproxen treatment was generally effective. Naproxen treatment in 12 patients with relapses lasted 25 months. However, 7 of these were not effectively treated with naproxen alone. Five were treated with oral glucocorticoids for 27 days in addition to naproxen, which induced remission in four, lasting for at least 1.5 years. Longitudinal growth of affected bones was not altered, except for the development of hyperostosis. Conclusion: CNO is a spectrum of inflammatory conditions, with CRMO being the most severe. Most children with CNO have a favourable outcome of the disease. Oral glucocorticoids may be necessary in severe recurrent cases.