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IOF World Congress News Osteogenesis imperfecta research highlighted at Lisbon congress – brittle bone disease affects both children and adults The loss of bone mass and resistance associated with osteoporosis, a disease largely affecting the elderly, may also occur in rare cases in a growing child. The condition of severe osteoporosis in a child is known as osteogenesis imperfecta, and seriously compromises growth and development. It affects 1 in 20,000 babies. Osteogenesis imperfecta is a genetic disorder characterized by bones that break easily, often from little or no apparent cause. The genetic defect present in patients – which may be inherited or may occur as a spontaneous mutation – affects the body's production of collagen, the major protein of the body's bone tissue that can be likened to the framework around which a building is constructed. In osteogenesis imperfecta, a person has either less collagen than normal or a poorer quality of collagen than normal, leading to weak bones that fracture easily. Prolonged immobility of affected children leads to further aggravation of bone loss, according to Dr. Francis H. Glorieux of Shriners Hospital for Children and McGill University, Montreal, Canada, who reviewed the disease and recent progress in its treatment during the IOF Congress on Osteoporosis in Lisbon. Children In children with osteogenesis imperfecta, specialized bone-forming cells or osteoblasts produce an abnormal bone matrix that is incapable of responding to mechanical loads. This leads to an increase in the population of osteoblasts and an associated increase in the activity of osteoclasts, the bone-eroding counterparts of osteoblasts. The result is the increased bone turnover rate that is characteristic of the disease. Osteogenesis imperfecta is, in most cases, associated with mutations in the genes encoding type I collagen, a major component of the bone matrix. However, these mutations neither correlate directly with disease severity nor account for all cases of the disease, implying that other, as-yet-unidentified, genetic causes are also likely to be implicated. Bisphosphonates are known to decrease bone turnover and reduce bone loss in adults, leading to the initiation of preliminary studies exploring their potential efficacy in juvenile patients. Early results obtained with intermittent intravenous pamidronate in children with have been extremely promising, according to Glorieux. Treated patients display increased bone mineral density and are able to increase their levels of physical activity with less associated pain and fewer bone fractures. Quality of life in pamidronate-treated patients consequently improved, while the treatment has not been associated with adverse effects on growth, bone modeling or fracture repair. Efficacy of the treatment is age-related, with greatest effects obtained in the youngest patients. Continued surveillance of patients is required in order to determine the drug's long-term effects on bone remodeling and bone tissue quality. Other bisphosphonate compounds may also be useful in treating osteogenesis imperfecta and are the subject of ongoing studies, he said. "In this disease, we understand that bisphosphonates are not a cure, but a remarkable improvement in quality of life and clinical evolution. We have to continue with the protocols," said Glorieux. Findings to date are encouraging and make it reasonable to consider, more now than ever, the exploration of further treatment options for this as well as other osteoporotic conditions in children. Adults Dr. Silvano Adami, Department of Rheumatology at the University of Verona, Italy and colleagues described the preliminary results of an ongoing clinical trial evaluating the bisphosphonate compound neridronate in adult patients with osteogenesis imperfecta. Bisphosphonates have been used successfully in the treatment of children with severe osteogenesis imperfecta, but this appears to be the first time that they have been administered to adult osteogenesis patients. Forty-six patients have been enrolled in the ongoing trial and are being treated once every three months with intravenous neridronate. Half of the patients began treatment immediately upon the first visit, while the other half began receiving neridronate only after 12 months of observation. Bone mineral density (BMD) of the lumbar spine and total hip were assessed and found to be unchanged in the latter group of patients during the first 12 months of the study, while patients in the former group had progressive increases in BMD of the lumbar spine and total hip up through year two. A trend toward a reduced incidence of clinical fractures was also reported as a result of i.v. neridronate therapy. However, the investigators stressed that further study is required in order to determine the real benefits of treatment with the bisphosphonate, including impact on bone fracture reduction and long-term preservation of bone mass. "Biphosphonates might provide real benefit for these patients," said Adami. "Intermittent i.v. neridronate induced significant increases in bone mass and decreased significant fracture rate in both growing and adult patients." Treatment is directed toward preventing or controlling the symptoms, maximizing independent mobility, and developing optimal bone mass and muscle strength. Care of fractures, extensive surgical and dental procedures, and physical therapy are often recommended for people with osteogenesis imperfecta. Use of wheelchairs, braces, and other mobility aids is common, particularly (although not exclusively) among people with more severe types of the disease. For more information on osteogenesis imperfecta, visit the Osteogenesis Imperfecta Foundation's website: www.oif.org
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