THU0545 A PROSPECTIVE OUTCOME OF ALL 17 CONSECUTIVE PEDIATRIC PATIENTS WITH CHRONIC NONBACTERIAL OSTEOMYELITIS TREATED WITH INTRAVENOUS PAMIDRONATE AND FOLLOWED AT A SINGLE CENTER OVER 15 YEARS
Authors: Paivi Miettunen, Chloe Stephenson, Seamus Stephenson, Xing Chang Wei
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> Intravenous pamidronate (IV-PAM) has been reported to be effective in pediatric patients with severe chronic nonbacterial osteomyelitis (CNO) in short term. Little is known about longterm outcome in CNO after IV-PAM. <h3>Objectives</h3> To describe a consecutive series of pediatric CNO (pCNO) patients who were prospectively followed after treatment with IV-PAM between 2003-2018 at a single center regarding: 1) The effect of IV-PAM on pain and Whole Body Magnetic Resonance Imaging (WBMRI) documented inflammation initially and after flare; 2) Relapse rate and; 3) Spinal CNO and 4) Urine N-telopeptide/creatinine ratio (UNtx/Cr) (a product of collagen 1 breakdown). <h3>Methods</h3> <h3>Patients</h3> All consecutive pCNO patients &lt;18 years at diagnosis, with WBMRI confirmed active disease who required IV-PAM between 2003-2018.<b>IV-PAM:</b> First dose 0.5 mg/kg; subsequent doses 1 mg/kg (maximum annual dose 11.5 mg/kg). IV-PAM was administered once monthly x 9. With confirmed flare IV-PAM was repeated (max 9 doses/year).<b>Pain response:</b> Visual analogue scale for pain (VAS) with "0" indicating no pain and "10" maximum pain was administered at baseline, at each IV-PAM treatment, and at suspected flare. <b>Imaging:</b> WBMRI before 1<sup>st</sup> IV-PAM, at 6 and 12 months, at suspected flare and after retreatment. CNO resolution was documented as complete (CR) if there was 95% improvement in the WBMRI signal. Spinal x-rays were performed at baseline and annually.<b>UNtx/Cr</b> was measured at baseline, after each IV-PAM and with suspected flare. <h3>Results</h3> 17 patients (9F, 8M) were included. The median [range] age at CNO diagnosis was 10.3[4-15] years, and at first IV-PAM 11.6[4-20] years. The median [range] follow-up was 9.2[1-15] years. Six patients had unifocal CNO, 4 had spinal CNO (2 with baseline vertebral fractures) and 6 had multifocal non-spinal CNO. VAS was uniformly 10/10 at baseline and decreased to 0-1/10 first month after IV-PAM. CR was achieved by all at 6 months, which persisted at 12 months. Four patients, 3 unifocal and one multifocal, had no further flares. Twelve patients had WBMRI confirmed flare at previously active sites at 9-36 months and 11 received 1-9 further doses of IV-PAM. With flare, VAS ranged from 4-9/10 and decreased to 0-3/10 within first month after re-initiation of IV-PAM. On final WBMRI, 12/17 (70%) had CR and 5/17 (30%) stable mild increased signal but no clinical symptoms. No further spinal compression fractures occurred. One patient required a third course of IV-PAM. Regarding UNtx/Cr, each patient had appropriate reduction after first IV-PAM. No patients flared while UNtx/Cr remained suppressed. Three patients developed arthritis and one acne. At last follow-up, 10/17 (59%) patients were on no medications, 4/17 (24%) required prn Naproxen for CNO and 3/17 (18%) were on Naproxen and/or disease modifying medications for arthritis. <h3>Conclusion</h3> Long-term follow-up of pCNO patients treated with IV-PAM confirms that while several patients eventually flare, the flares are less painful and have an excellent response to IV-PAM retreatment. No further spinal fractures occurred. No flares occurred while UNtx/Cr remained suppressed, suggesting a role of osteoclasts in CNO. Further prospective multicenter studies are now required to define the long-term clinical and imaging response to IV-PAM. <h3>Disclosure of Interests</h3> None declared