The key features of chronic nonbacterial osteomyelitis (CNO) or chronic recurrent multifocal osteomyelitis (CRMO) have been identified in a bid to help separate the condition from its mimickers.
The comparison of clinicopathologic and imaging features from a multinational case-control study, comprising 450 children and young adults from 20 centre across seven countries, were presented at ACR Convergence 2020.
Paediatric rheumatologist Dr Dan Zhou, from the Seattle Children’s Hospital and University of Washington, told the meeting CNO was sometimes very difficult to distinguish from growing pains, infection or cancer.
“The disease itself can be very damaging because it is difficult to diagnose – up to two years of delay from the start of bone pain until diagnosis.”
“Fracture in the spine is one of the common complications and also it may affect the legs causing one leg to be shorter than the other,” he said.
The study, funded by ACR and EULAR, found CNO patients were predominantly female and more frequently exhibited intermittent versus continued pain, especially of the neck, back and upper torso. Clavicular swelling was also more common in CNO.
CNO patients more frequently had whole body imaging – usually whole-body MRI – and symmetric patterns of bone lesions were more common in CNO than in mimicker conditions (53% v 19%).
CNO frequently involved the thoracic spine, clavicle, sternum/manubrium, pelvic bones, bilateral femur, bilateral tibia, unilateral fibula, and foot bones.
Features against a diagnosis of CNO included fever (16% v 31%), laboratory tests suggestive of infection, or pathology from a bone biopsy indicating malignancy.
Specific imaging features suggestive of infection or malignancy included cortical bone disruption, disorganised bone formation, mass structure, marrow infiltrate, abscess or geographic appearance.
Active arthritis was more common in controls as was a complete and sustained response to antibiotic treatment (23% v 52%).
Dr Zhou said the findings will help inform the development of future classification criteria following an expert panel discussion and a 1000 Minds process. A separate cohort of cases would be needed to help validate the new classification criteria.