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Unifocal and multifocal chronic non-bacterial osteomyelitis (CNO) in children


Chronic non bacterial osteomyelitis (CNO) is a rare condition in children and little is known about its clinical assessment and course.


To describe the clinical characteristics and long-term outcome of pediatric patients with CNO.


We retrospectively evaluated patients with sterile bone inflammation, lasting longer than 6 month, referred to two tertiary care pediatric rheumatology units. Information on family history, clinical features at disease onset and course, laboratory and outcome were collected. A comparison between unifocal (UF-CNO) and multifocal course (MF-CNO), based on bone scintiscan result, was performed.


29 CNO patients entered the study. Ten had UF-CNO, 19 had MF-CNO, mean age at disease onset 9,2 years (range 0,8-17), males (52%). Disease duration at diagnosis was longer in pts with UF-CNO (11,1 vs 4,6 months). Localized bone pain was the leading symptom at onset in all patients; systemic symptoms, such as fever and fatigue, were more frequent in MF-CNO. 30% presented associated skin disease and positive family history for autoimmune disease. At onset WBC normal, CRP was elevated in 38%, ESR in 72%, especially in MF-CNO. Scintiscan allowed us to identify multiple lesions in five patients with one-site symptoms. MF-CNO involve more frequently the lower limbs than the UF-CNO (18/19 vs 4/10, p 0,001). After three years follow up, 70% of patients had no symptoms and 90% were off-therapy. UF-CNO developed complications, such as hyperostosis, vertebral collapse or limb dysmetry, significantly more often than MF-CNO (p 0,002).


UF-CNO and MF-CNO belong to the same spectrum but present different clinical features and outcome.

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Correspondence to G Zanon.

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This article is published under license to BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Zanon, G., Insalaco, A., Martini, G. et al. Unifocal and multifocal chronic non-bacterial osteomyelitis (CNO) in children. Pediatr Rheumatol 9 (Suppl 1), P32 (2011).

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