E066 The use of zoledronate in CRMO: a small case series

Background/Aims Chronic Recurrent Multifocal Osteomyelitis (CRMO) or Chronic non-bacterial osteomyelitis (CNO) is a rare inflammatory bone disorder mainly affecting children and young adults. The time from onset of symptoms to diagnosis is often delayed due to variety of reasons. There is little evidence for treatment of this condition, which is often empiric, based on personal experience, expert opinion, case reports or small case series. In 2018, the Eurofever registry published the largest case series and complete remission of symptoms was largest in the group of patients treated with bisphosphonates (51%). Much of the available evidence about the use of bisphosphonates is with pamidronate. However, zoledronate has been increasingly used due to its efficacy in other bone disease, longer duration of action, and possibly fewer infusions. In this small case series, we aimed to review the response of patients with CRMO to zoledronate. Methods This was a retrospective study, collecting data from electronic medical records of 8 consecutive patients with CRMO treated with zoledronate by the Paediatric Rheumatology team at Nottingham Children’s Hospital since 2021. Results 8 patients treated with zoledronate were identified. Of these 3 (37.5%) were female and 5 (62.5%) were male. Additional demographic data was unavailable for 1 patient. In the remaining 7 patients the age of onset of symptoms ranged from 6 years to 14 years with a mean age of onset of 9 years. The length of symptoms before rheumatology review ranged from 2.5 months to 36 months with a mean of 13 months. The commonest sites involved were Femur (71%), followed by mandible (42%) and pelvis (29%). All 8 patients had received a trial of NSAIDS before receiving zoledronate. All patients received concurrent treatment with IV methylprednisolone along with zoledronate. The indications of zoledronate treatment were symptoms persisting despite NSAIDs and spinal lesions, even if asymptomatic. The protocol involves giving a single dose of zoledronate with subsequent doses given only if there is a clinical and / or radiological flare. No patients reported significant side effects. 7 (87.5%) patients had a response to zoledronate. 6 patients have received only 1 infusion of zoledronate. 1 patient received 3 zoledronate infusions in total with a second dose given 12 months after the first one and the third dose 16 months following the second. The other patient had two zoledronate infusions 12 months apart. Conclusion The data confirms previous evidence that bisphosphonates are a safe and effective treatment in children and adolescents with CRMO, with zoledronate specifically being effective without significant side-effects. As this is a retrospective study there were limitations to the data collected. Prospective studies looking at the treatment of CRMO are needed to help develop a standard approach to management of these patients. Disclosure M.C. Mackay: None. S. Deepak: None. K. Gargh: None. S. Rangaraj: None. K. Warrier: None.