FRI0530 Efficacy and Tolerability of Pamidronate in Chronic Recurrent Multifocal Osteomyelitis

Background Chronic recurrent multifocal osteomyelitis (CRMO) is a rare autoinflammatory disease in children. First-line treatments used are nonsteroidal anti-inflammatory drugs (NSAIDS). Secondary treatments after NSAIDS in case of refractory CRMO are not standardized and have been few evaluated. Biphosphonates, in particular pamidronate, have been used off label in a limited number of patients1. Objectives A retrospective survey and chart review to evaluate the reasons for use, the efficacy and the tolerability of IV pamidronate in 13 patients with difficult CRMO. Methods Thirteen of the 30 patients followed in the pediatric rheumatology unit at Bicêtre hospital, were analyzed retrospectively. Pamidronate treatment was documented as follows: reasons for its use, administration scheme, clinical efficacy (pain was evaluated by visual analog scale (VAS) and tolerability. Radiological changes were evaluated where available. Results Thirteen patients (4M, 9F) were treated by pamidronate from November, 2004. The median age at treatment was 10 years (6-14 years). Pamidronate was administered, on demand, intravenously by cycles of 3 consecutive days (0.5 mg/kg at J1, then 1 mg/kg at J2 and J3), following the protocol for osteogenesis imperfecta. Eleven patients received from a single cycle, 1 patient received 4 cycles and 1 patient 6 cycles. Pain resistant to oral and IV NSAIDS was the main reason for all the patients. VAS was 6/10 before pamidronate, and 0/10 36 hours after pamidronate infusion for 11/13 patients. Pain persisted for 1 patient and disappeared after 3 weeks for another one. The clavicle swelling disappeared in 1/5 patients and clearly decreased in 4/5 patients. The median duration of symptom-free intervals between 2 crises was 10 months (1-21.6). Five patients had a MRI after pamidronate treatment, which showed a decrease of the number of the lesions for 4 of them. The main side effects of pamidronate infusions were mild and transient: fever (n=9) with 5 flu-like symptoms, hypocalcaemia (>2mM, n=6; 2 mM, n=5, and 2 were symptomatic). Conclusions Our observations show that about 1/3 of patients with CRMO may present difficult to treat acute attacks of bone pain. In these cases, pamidronate appears to be the best pain relieving treatment with a rapid time of response and with limited side effects. References Miettunen PM, Wei X, Kaura D, Reslan WA, Aguirre AN, Kellner JD. Dramatic pain relief and resolution of bone inflammation following pamidronate