LAUSR

Background Chronic recurrent multifocal osteomyelitis (CRMO) is a rare autoinflammatory polygenic bone disease characterised by aseptic bone inflammation in paediatric population. Its management, clinical, radiological findings and treatment have not yet been standardised. Objectives Retrospective, descriptive multicentric study of patients diagnosed of CRMO in four tertiary level hospitals’ paediatric rheumatology section. There were 16 patients included. The clinical, radiological characteristics where analysed as well as response to treatment options. Results The median age at diagnosis was 10,5 years, female:male ratio 62,5:37,5%. The delay in the diagnosis had a median of 4.5 months, being less than one year in 11 patients. Bone pain was the first symptom in 100% of the patients accompanied by fever in 25% of them. A single patient presented perilesional arthritis. A slight-moderate increase on acute fase reactants was observed at the debut of the disease: median ESR 47.5 mm/h. The median number of locations at debut was 2.5 (range 1–14), with multifocal involvement in 75%. The most frequent location was tibia (56%), followed by pelvis (44%) and vertebrae (31,25%). Other locations less fenquent were: carpus (12.5%), femur (12.5%) mandible (6%) and sternum (6%). Biopsy was performed in 14/16 patients and bone scintigraphy with Tc99 in 12/16 patients, with pathological uptake observed in 91.6% of cases. MRI was the radiological test of suspected diagnosis in 15/16 patients. NSAIDs were the initial treatment. 5 patients received different antibiotic therapy regimens, without clinical or radiological improvement. 56.25% of patients required other treatments. Systemic corticosteroids were used in 12.5% of patients and bisphosphonates in 43.75% (100% of patients with axial involvement). After 6 months of treatment with biphosphonates, 57.14% had complete remission, 28.57% partial remission and 14.28% worsening. 12.5% of the patients had a torpid evolution, receiving sequential therapies with multiple synthetic or biological DMARDs (Anakinra, Canakinumab, Etanercept), and another 12.5% required surgery. Conclusions The diagnosis of CRMO is a challenge in the absence of pathognomonic features which leads to delay in diagnosis and the initiation of treatment. In our centres the biphosphonates were the treatment strategy used in patients with spinal involvement with 85.67% response at 6 moths. Disclosure of Interest None declared