ESPE Abstracts

Introduction: Chronic non-bacterial osteomyelitis (CNO) is a sterile inflammatory disease of the skeleton characterized by local pain and swelling. If first line treatment (non-steroidal anti-inflammatory drugs) fails, bisphosphonates are recommended. There are no randomized controlled studies so far that would clarify the zoledronate efficiency, and also no study systematically exploring the effect on bone mineral density (BMD).

Methods: We have applied standardized protocol in our center since 2021. All patients with CNO undergo whole body magnetic resonance imaging (WBMR) and bone densitometry using dual energy x-ray absorptiometry (DXA) and peripheral quantitative computerized tomography (QCT) before and one year after the start of treatment with intravenous zoledronate. The doses were 0.025 mg/kg and 0.05 mg/kg body weight at first and second application, respectively, six months apart. Patients with other coincident diseases affecting the skeleton were excluded from this analysis.

Results: There were 23 children with CNO who started the protocol, of whom 15 finished the first year so far. Their mean age at first zoledronate application was 11.3 years (range 5-18 years). The repeated bone densitometry at year 1 was available in 12/15 (DXA) and 10/15 (pQCT) children, respectively. At study start, both mean lumbar spine areal BMD Z-score as well as mean trabecular volumetric BMD Z-score were normal (-0.4±1.1; P=0.22 and -0.5±1.1; P=0.13, respectively). Whereas lumbar spine areal BMD Z-score significantly increased after two doses of zoledronate (-0.4±1.1 vs. 0.8±1.4; P=0.033), trabecular volumetric BMD Z-score did not change (-0.5±1.1 vs. 0.04±2.0; P=0.43).

Conclusion: Zoledronate treatment of children with CNO leads to increase in lumbar spine areal BMD already after the first two applications. Whereas the rheumatologist‘s main focus is pain relief, diminished swelling and regression of the skeletal lesions on WBMR, potential side effect such as increased BMD and related osteopetrosis-like bone fractures shouldn’t escape the attention.