Abstract
Chronic nonbacterial osteomyelitis (CNO) is an auto-inflammatory bone disorder with a wide spectrum of clinical manifestations, from unifocal to multifocal lesions. When it manifests with multifocal lesions, it is also referred to as chronic recurrent multifocal osteomyelitis (CRMO). CNO/CRMO can affect all age groups, with the pediatric population being the most common. Patients may present with systemic inflammation, but there is no pathognomonic laboratory finding. Magnetic resonance imaging (MRI) is the gold standard radiological tool for diagnosis. In the absence of validated diagnostic criteria, CNO/CRMO remains an exclusion diagnosis. Bone biopsy does not show a specific disease pattern, but it may be necessary in unifocal or atypical cases to differentiate it from malignancy or infection. First-line treatments are non-steroidal anti-inflammatory drugs (NSAIDs), while bisphosphonates or TNF-α blockers can be used in refractory cases. The disease course is unpredictable, and uncontrolled lesions can complicate with bone fractures and deformations, underlying the importance of long-term follow-up in these patients.
Highlights
Chronic nonbacterial osteomyelitis (CNO) is an auto-inflammatory bone disorder, first described in 1972 by Giedion et al [1] as a subacute and chronic symmetrical osteomyelitis.CNO is an umbrella term that includes conditions manifesting with a wide range of clinical manifestations, from single to multiple bone lesions [2]
Several other definitions have been used over time to refer to this heterogeneous disorder, such as chronic recurrent multifocal osteomyelitis (CRMO), synovitis acne pustulosis hyperostosis osteomyelitis (SAPHO) syndrome, and nonbacterial osteomyelitis [3]
The elevation of inflammatory markers in CNO/CRMO is usually moderate, and it resolves during inactive periods [5]
Summary
Chronic nonbacterial osteomyelitis (CNO) is an auto-inflammatory bone disorder, first described in 1972 by Giedion et al [1] as a subacute and chronic symmetrical osteomyelitis. CNO is an umbrella term that includes conditions manifesting with a wide range of clinical manifestations, from single to multiple bone lesions [2]. Several other definitions have been used over time to refer to this heterogeneous disorder, such as chronic recurrent multifocal osteomyelitis (CRMO), synovitis acne pustulosis hyperostosis osteomyelitis (SAPHO) syndrome, and nonbacterial osteomyelitis [3]. As CNO is a rare disease, and presents with a wide spectrum of manifestations, the diagnosis can be challenging. Clinical presentation, laboratory and radiological investigations, pathophysiology, and treatment options will be discussed
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