Chronic nonbacterial osteomyelitis: report of thirteen cases

Introduction: Chronic Nonbacterial Osteomyelitis (CNO), also known as Chronic Recurrent Multifocal Osteomyelitis (CRMO), is a rare autoinflammatory bone disorder that causes multifocal or unifocal aseptic lytic lesions in bone biopsy and is characterized by periodic exacerbations and remissions of sterile osteomyelitis. The aim of this report was to describe clinical features, subsidiary exams, treatment and outcome of thirteen cases of CNO followed in a tertiary center in Brazil. Methods: We carried out a single-center retrospective descriptive review of clinical records, including thirteen children and adolescents with CNO followed between 2010 and 2020 in our tertiary service in Brazil. Medical records were reviewed in order to collect data about clinical presentation, inflammatory markers, radiological and histological findings, treatment and outcome.The diagnosis of CNO was based on the Bristol diagnostic criteria for CRMO. Results: Thirteen patients were included in this study, of whom 46% were female. Median of current age and of follow-up time were 11 years (range 8.5-20.4) and 40 months (range 9-123), respectively. Median age at disease onset was 8.1 years (range 0.8–15.3) and median age at diagnosis was 11 years (range 7-16.1). The most affected sites were metaphysis and diaphysis of long bones. Median number of initially affected bones was 4.0 (range 1-7). Five patients had recurrences. All patients had increased acute phase reactants at disease onset. All patients had at least one of the characteristic findings on MRI (lytic lesions, osteitis, hyperostosis and periostitis). Five patients received systemic glucocorticoids, eight received methotrexate and seven received bisphosphonates (alendronate). Conclusion: The awareness of the features of CNO is important for an early diagnosis and may avoid unnecessary diagnostic procedures and prolonged antibiotic therapies.