Chronic recurrent multifocal osteomyelitis (CRMO) is a rare disease characterized by sterile bone inflammation. It is an orphan disease with many unclear aspects in terms of diagnosis, treatment and follow-up. The aim of this study was to report our experience of pediatric CRMO patients. Children who were diagnosed with CRMO, and were followed-up between January 2008 and January 2017, were included in this study. There were 15 CRMO patients (8M/7F) with a median age at diagnosis of 9.0 years (range: 0.6-15.0). Bone pain was the most common presenting symptom. All of the patients had multifocal bone lesions. Vertebrae (66.7%) and femur (66.7%) were the most commonly affected bones. Eight of the patients also had sacroiliitis; however, only one of them was HLA-B27 positive. Whole-body magnetic resonance imaging (MRI) was used as a diagnostic tool in 13 patients revealing bone marrow edema (84.6%), osteitis (69.2%), and periosteal reaction (61.5%). All patients were initially treated with non-steroidal anti-inflammatory drugs (NSAIDs), however, disease-modifying anti-rheumatic drugs, anti-TNF agents or pamidronate were added to therapy due to inadequate treatment response. Clinical remission was achieved in 12 patients (1 with NSAIDs, 3 with methotrexate, 1 with pamidronate and 7 with an anti-TNF agent). During the follow-up period, relapses were observed in four patients who presented with pain and/or a newly formed bone lesion on MRI. Eventually, however, all of these patients also reached remission. CRMO is a chronic disease which may have a progressive or relapsing-remitting course. Improvement of the knowledge about this rare disease may help to enlighten the unknowns of the disease.

Keywords: CRMO, chronic recurrent multifocal osteomyelitis, treatment