Initial evaluation of the child with insidious-onset localized bone pain and suspected chronic nonbacterial osteomyelitis (CNO)/chronic recurrent multifocal osteomyelitis (CRMO)

ALP: alkaline phosphatase; CBC: complete blood count; CRP: C-reactive protein; ERA: enthesitis related arthritis; ESR: erythrocyte sedimentation rate; GPA: granulomatosis with polyangiitis; Hg: hemoglobin; IBD: inflammatory bowel disease; LCH: Langerhans cell histiocytosis; LDH: lactate dehydrogenase; MRI: magnetic resonance imaging; PPP: palmoplantar pustulosis; WBC: white blood cell.

* Findings on plain radiograph, including periosteal reaction and lytic lesions, are usually confirmed by an MRI with contrast of the affected area. MRI may show ring enhancement.

¶ Elevated LDH and/or uric acid suggests tumor lysis syndrome. Cutoffs for both labs vary by age.

Δ In patients with leukemia, plain radiographs often show metaphyseal bands and a periosteal reaction. Radiographs in patients with LCH may show osteolytic lesions as a "punch-out" pattern. In non-LCH histiocytosis, bilateral and symmetric osteosclerosis of the diaphysis of the long bones is nearly universal. Findings on plain radiograph are usually confirmed by an MRI with contrast of the affected area. Cortical destruction/disruption is more common in malignant bone tumors and is seen in some infections. It is not seen in CNO/CRMO.

◊ Mixed osteolytic and sclerotic lesions, primarily affecting long bone metaphyses, are one of the most common radiographic findings in patients with CNO/CRMO. Other radiographic findings include periosteal reaction, cortical bone thickening, sclerosis, and hyperostosis.

§ CNO/CRMO is associated with other conditions that primarily affect the skin, gut, or joints, such as psoriasis, PPP, acne, IBD, spondyloarthropathy/ERA, and, less commonly, pyoderma gangrenosum, Sweet syndrome, Takayasu arteritis, or GPA.

¥ If fever is present, assess for both malignancy and infection.