Treatment Advances in Chronic Non-Bacterial Osteomyelitis and Other Autoinflammatory Bone Conditions

Abstract

Chronic non-bacterial osteomyelitis (CNO), also known as chronic recurrent multifocal osteomyelitis (CRMO), is an autoinflammatory bone disorder that primarily affects children. CNO mainly affects long bones in the lower extremities, vertebral bodies, clavicle, mandible, and pelvic bones. No laboratory biomarker has been shown reliable for clinical monitoring yet. Imaging especially whole-body MRI with STIR images has become the gold standard of monitoring disease because of its sensitivity to detect active lesions. In children with suspected CNO, regional MRI at minimum is recommended to determine the presence of bone edema and adjacent soft tissue inflammation and/or periosteal reaction. Basic laboratory workups are usually performed by referring physicians to screen for malignancy and infectious osteomyelitis. When a child has CNO-associated conditions such as psoriasis, inflammatory bowel disease, or multiple CNO lesions in characteristic sites, a bone biopsy may be postponed. However, in children with a unifocal lesion other than clavicle or ill appearance, an MRI-guided bone biopsy with bacterial, fungal, and mycobacterial cultures as well as pathology review is strongly recommended to exclude alternative diagnoses. Nonsteroidal anti-inflammatory drugs (NSAIDs) remain the first-line treatment. However, non-responders and children with frequent relapses require other treatments such as short-term glucocorticoids, disease-modifying anti-rheumatic drugs (DMARDs), TNF-α inhibiters, and/or bisphosphonates. In children with associated arthritis without sacroiliitis, DMARDs may be considered for both conditions. In children with sacroiliitis and CNO, TNF-α inhibiters are preferred. When active spinal lesions are present, bisphosphonate may be chosen as first-line treatment or used in combination with other agents. Repeated MRI is recommended to determine the response to treatment because pain relief can occur despite persistent bone inflammation. Long-term follow-up is recommended as some patients continue to have ongoing disease activity into adulthood.