Clinical characteristics and treatment outcomes of chronic recurrent multifocal osteomyelitis in the population of children from central Poland – observations of one center

Introduction
Chronic recurrent multifocal osteomyelitis (CRMO) is a rare autoinflammatory disease that occurs predominantly in the paediatric population. The disease causes recurrent flares of inflammatory bone pain and typically affects multiple bones. The aim of the study was to evaluate demographic and laboratory data, the overall clinical picture and treatment responses among children and adolescents with this disease entity from central Poland.

Material and methods
A total of 25 children diagnosed with CRMO between 2016 and 2022 at the Department of Paediatric Cardiology and Rheumatology at the Medical University of Łódź were enrolled in the study. A comprehensive, retrospective review of the clinical, laboratory and radiological data was conducted.

Results
The median age of onset of the disease was 12 years (range 4–17). The vast majority of patients (68%) were female. The incidence rate of CRMO in central Poland was found to be approximately 1.7/100 000 children/year. 60% of the patients had more than one lesion at the disease onset and male patients were more likely to present with multifocal disease. The most frequently affected bones were tibia (52%) and femur (36%). The mean inflammatory marker values were within normal limits, while the osteocalcin concentration in all of the patients was elevated over the normal range (median concentration 92.4 ng/ml (IQR: 62.6–116.45)). Most of the patients (68%) underwent a whole-body magnetic resonance imaging (MRI) scan that revealed abnormal bone activity of the affected structures. The patients were successfully treated with non-steroidal anti-inflammatory drugs (56%), methotrexate (44%), sulfasalazine (64%) and bisphosphonates (32%).

Conclusions
Although awareness of CRMO is increasing among clinicians, data from the Polish population is still limited. This study analysed the clinical features, laboratory tests, imaging methods and treatment outcomes. Whole-body MRI has been identified as a relevant screening tool for the diagnosis of CRMO. Further research on CRMO is needed in order to increase awareness and consequently reduce the time to diagnosis.