Osteogenesis imperfecta : Anthropometric, skeletal and mineral metabolic effects of long-term intravenous pamidronate therapy

Administration of bisphosphonates represents a beneficial therapy in children and adolescents with severe osteogenesis imperfecta (OI) because it significantly reduces the annual rate of bone fractures. To evaluate the anthropometric, skeletal and mineral metabolic effects of long-term intravenous pamidronate therapy in OI. Ten patients, aged 5 mo to 25 y, with OI received cyclical intravenous pamidronate. The yearly dose of pamidronate was approximately 9 mg/kg/d at all ages. Duration of treatment varied from a minimum of 2 y to a maximum of 5 y. Growth, bone mass and mineral metabolic parameters were studied at baseline and repeated every year thereafter. Bone mass was assessed by calculation of bone mineral apparent density (L2-L4 BMAD). This represents the first study on the changes in size-adjusted measures of bone mass observed with such therapy. While on therapy, all children and adolescents grew normally but did not experience any manifest catch-up growth. A significant decrease in the incidence of bone fractures was observed. In seven patients with severe forms, L2-L4 BMAD increased by 80% after the first 2 y of therapy but tended to stabilize or even decrease over the following years despite maintenance of therapy. A significant inverse correlation could be established between urinary Ca excretion and L2-L4 BMAD (r = -0.30, p < 0.05). Our results confirm that cyclical pamidronate infusions reduce the incidence of bone fractures and allow normal growth. The improvement in bone mass initially observed after the first 2 y of therapy is not always sustained over the following years despite maintenance of therapy.