ESPE Abstracts

Osteogenesis imperfecta (OI) is a rare genetic disease characterized by bone fragility and an increased risk of fractures. Intravenous bisphosphonates are the current gold standard for the treatment of OI: the aim of this therapy is an increase in Bone Mass Density (BMD) and a consequent reduction in pathological fracture rates. Currently, the only bisphosphonate approved in Italy for pediatric population is neridronate, infused in hospital once every four months. In San Raffaele Hospital (Milan) 14 children with OI are currently being treated, seven of which with neridronate therapy with an average of 7.5 years of treatment. Patients treated with neridronate are showing an increase of BMD greater than the one expected for their normal skeletal growth (which is 3.5-5.7% per year): we observed an increase of 16-20% in the first year of therapy, 8-20% in the following years. These children also had a decrease in bone turnover with significant reductions in total serum ALP, urinary calcium, NTx and CTx. Those markers started to decrease in the first 3-4 months of therapy, so they could be considered useful as an early sign of the effectiveness of bisphosphonate therapy. We found a reduction in the incidence of fractures, averaging from 1.24 pre-treatment fractures per patient/year to 0.73 fractures during treatment per patient/year; in addition, many of the fractures that occurred during treatment were less severe and occurred for more severe trauma than the pre-treatment ones. One patient, that had the highest number of fractures, did not have a marked improvement with bisphosphonate therapy. We did not observe an increase in height in SDS in most of our patients, indicating that it is unclear how much bisphosphonate treatment affects growth. The therapy was well tolerated by our patients with no significant adverse effects. Our data are in line with many randomized and controlled studies about the effectiveness of bisphosphonates in OI, showing that BMD increases and biochemical markers of bone turnover decrease compared to the absence of treatment. The data about the reduction of fracture rate are conflicting in many studies: the effectiveness is still uncertain since it is difficult to distinguish the true effects of bisphosphonates by the effects that come from skeletal growth and the protective measures applied to prevent trauma. Further randomized, placebo-controlled clinical trials will be needed to evaluate the effectiveness of bisphosphonates in reducing the incidence of fractures in patients with OI.