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Bisphosphonates in osteogenesis imperfecta
  1. N J SHAW
  1. Metabolic Bone Disease Clinic
  2. Department of Endocrinology
  3. Birmingham Children’s Hospital
  4. Ladywood Middleway, Ladywood
  5. Birmingham B16 8ET

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    Editor,—I was interested to read the recent articles by Allgrove1 and Williams et al 2 on the use of bisphosphonates in children and would like to report my experience of their use in a child with osteogenesis imperfecta. The patient was referred to me age 9 years with a history of recurrent fractures since infancy and a family history consistent with osteogenesis imperfecta. She had a nine month history of low back pain, evidence of a thoracolumbar kyphosis, and tenderness over the thoracolumbar spine. She had become wheelchair bound following a fractured femur three months previously and a recent hospital admission with urinary and faecal incontinence was associated with upper motor neurone signs in her legs. Radiography of her spine showed collapse of numerous vertebrae in the thoracic and lumbar spine with marked osteoporosis. Routine biochemistry showed no abnormality of serum calcium, phosphate, alkaline phosphatase, parathyroid hormone, or 25-hydroxyvitamin D and a normal urine calcium/creatinine ratio. Bone density of the lumbar spine (L2–L4), using a Lunar DPX-L DXA scanner with the paediatric software, was 0.395 g/cm2 with a Z score for age of −4.0. After discussion with her parents it was decided to treat her with bisphosphonates. This was initially with pamidronate 0.5 mg/kg given intravenously every three months for six months which was then increased to 1 mg/kg/day for two consecutive days for a further six months. Because of difficulties with venous access this was then changed to etidronate given orally for a period of two weeks in every three month period in a dose of 600 mg/day (9 mg/kg) which has continued for the past nine months. No adverse effects were seen during the period of treatment.

    The change in bone density during this period is indicated in table 1. There was a 44% increase in the bone density of the lumbar spine with no further fractures occurring during this time. This has been accompanied by a progressive improvement in her mobility such that she is now walking with the aid of a rollator and uses the wheelchair only for long distances. She now has no evidence of spinal deformity. Although it could be argued that some of this improvement was due to the onset of puberty, the improving Z score indicates an effect independent of changes in body size. Thus this case supports other reports indicating the potential benefits of bisphosphonates in osteogenesis imperfecta, although it is important that there is careful selection of cases, and as indicated by Allgrove that monitoring of bone biochemistry and density is undertaken. The need for appropriate informed consent is also essential.

    Change in bone mineral density (BMD)

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