Bone Abstracts

Osteogenesis imperfecta (OI) is a rare genetic disorder characterized by fragile bones susceptible to fractures. No definite cure for OI exists. Bisphosphonates, although not implicitly recommended in children due to deficient efficacy and safety data, have been administered off-label to OI patients for over 20 years. Short-term adverse effects of intravenously administered bisphosphonates are generally mild. Although anemia is a known side effect of bisphosphonates in adults, thus far no study has evaluated or described this potential adverse reaction to intravenous pamidronate in children with OI. The aim of the study was to evaluate short-term adverse effects resulting from intravenous pamidronate administration in children with OI, with special regard to hematologic parameters. We retrospectively analyzed clinical data from 313 pamidronate administrations in 60 pediatric patients diagnosed with OI, treated at Department of Pediatric Propedeutics and Metabolic Bone Diseases, Medical University of Lodz. Median age across all analyzed treatment cycles was 6 years, with the youngest child being 11 days old and the oldest 17.8 years old at the moment of pamidronate administration. Fever, flu-like syndrome on first infusion and mild hypocalcemia occurred most frequently during the first infusion. Most children experienced changes in blood morphology, with a significant hemoglobin level reduction (median 12.8 g/dL before vs 12.1 g/dL after administration; P<0.01) consistent with a decrease of red blood cell count (median 4.7×106/mL before vs 4.5×106/mL after administration; P<0.01). In 64 out of 313 analyzed cycles, children experienced anemia following pamidronate infusion. Intravenous pamidronate administration is therefore associated with lowering of red blood cell parameters in children with osteogenesis imperfecta. This effect is currently under-appreciated and should be taken into account by physicians administering pamidronate off-label to OI patients. The precise mechanism and clinical relevance of these findings warrant further investigations.

Disclosure: The authors declared no competing interests.