PP18. A case series of chronic non-bacterial osteomyelitis

Abstract

Background: Chronic non-bacterial osteomyelitis (CNO) describes a spectrum of autoinflammatory bone disorders, characterized by single or multiple bony inflammatory lesions that can be monophasic or recurrent. When lesions are multiple and recurrent, the disease is termed chronic recurrent multifocal osteomyelitis (CRMO) [1, 2]. Aim(s): This study aims to describe CNO/CRMO patients managed by the Paediatric Rheumatology Department at Leeds General Infirmary over the last 4 years. Method(s): Retrospective case notes review, focusing on patterns of referral, and clinical and radiological presentations. Result(s): Eight patients, with a median age of 11.5 years (range 7-18) were identified. Five patients were first referred to Orthopaedics, three to General Paediatrics and one to Paediatric Neurology. Paediatric Oncology was also involved in the early pathway of two patients. The median time between presentation of symptoms and referral to Paediatric Rheumatology was 24 months (range 12-72). The median time between symptom presentation and diagnosis of CRMO was 30 months (range 12-84). The most common presenting symptoms were intermittent pain and swelling. The degree of pain was variable and, in many, pain was exacerbated by exercise. The most common sites of lesions at presentation were the clavicle (3/8) and pelvis (3/8). All patients were investigated by X-ray imaging, seven had gadolinium contrast and STIR MRIs, and two also had an isotopic bone scan. In every patient, MRIs detected more lesions than X-rays, and in three patients MRI picked up lesions that were unexpected clinically. Bone biopsies were performed in six patients, of which two were inconclusive and four aided diagnosis by excluding malignancy and infection. ESR was raised in most patients. Five patients were treated first-line with NSAIDs; naproxen and diclofenac were the most common choices. Two patients received antibiotics, with no effect on CRMO lesions, and one had oral prednisolone. One patient also received MTX. Pamidronate infusions were either administered or planned in five cases. Conclusion(s): There were significant delays in referrals to Paediatric Rheumatology, which contributed to delay in diagnosis of CNO/CRMO. The most common sites of presenting lesions were the clavicle and pelvis, and the vertebral column was often involved. MRI with gadolinium was the most useful investigation leading to diagnosis; it also helped to monitor disease progression and response to therapy. MRIs showed many lesions that would have gone undetected if only a plain radiograph had been performed. In our experience, patients can be mildly symptomatic in terms of pain and functional impairment, in spite of significant radiological changes.