Chronic nonbacterial osteomyelitis: a typical case and review.

Background: Chronic Non-bacterial Osteomyelitis (CNO) is a rare autoinflammatory bone disease primarily affecting children and adolescents. The disease presents with a wide spectrum of severity, ranging from mild unifocal lesions to severe, recurrent multifocal bone inflammation. Its etiology remains unclear, making diagnosis challenging due to nonspecific symptoms. Methods: We report the case of a 14-year-old girl who presented with recurrent swelling and pain in the left clavicle. After multiple admissions, the patient underwent extensive diagnostic workup, including laboratory tests, imaging, and biopsies, which showcased typical imaging and histopathological findings throughout the disease progression, helping to rule out infections and malignancies. Based on clinical findings and the exclusion of other conditions, she was diagnosed with CNO. Treatment included NSAIDs, intravenous antibiotics, and oral medications such as diclofenac sodium, naproxen, methotrexate, and calcitriol. Results: During the one-year follow-up after initial treatment, the patient experienced recurrent symptoms, including swelling and pain in the left clavicle. After escalation to intravenous pamidronate and subcutaneous adalimumab, the patient achieved sustained clinical remission. During the subsequent two-year follow-up, no further symptom recurrence was observed. Conclusion: CNO is generally diagnosed by exclusion, with MRI being the gold standard for detecting asymptomatic lesions and assessing disease activity. Treatment typically involves NSAIDs, with bisphosphonates and biologics increasingly used in refractory cases. This case underscores the complexity of diagnosing and managing CNO, highlighting the need for a multidisciplinary approach. Further research is essential to establish standardized diagnostic criteria and optimize treatment strategies for this rare condition.