Idiopathic juvenile osteoporosis (IJO) is a rare, self-limited disease, first described in 1965 by Dent and Friedman (20). IJO reveals itself in otherwise healthy children, more often 2 to 3 years before puberty, even if more precocious cases are observed (21). It does not appear to be hereditary and is equally distributed among genders. Affected children have pain in the back, pelvis, knees, feet, and sometimes have difficulties in walking. Compression vertebral fractures are frequent and may reduce the trunk's length. Long bone fractures, more commonly at metaphyses, are also observed. Clinical examination may reveal kyphosis, scoliosis, pigeon chest, long bone deformities and the already mentioned difficulties in walking.
The pathognomonic feature of IJO is the radiological evidence of impaction-type fractures, typically located at weight-bearing metaphyses (e.g. distal tibiae), and characterized by abnormal newly formed bone (neo-osseous osteoporosis). Long bones have no alteration in dimensions, while vertebral bodies may present height reductions because of biconcave or wedge deformities. There are no relevant laboratory anomalies, except possible nonspecific alterations of bone turnover markers. The diagnosis of IJO is based on the exclusion of other forms of osteoporosis. The differential diagnosis between IJO and the mild forms of Osteogenesis imperfecta may be difficult. The most characteristic clinical feature of IJO is its spontaneous resolution within 2 to 5 years, more frequently occurring at puberty. In some cases, however, the disease persists in adult age (22).
Pathogenesis is not known. Recent histomorphometric studies on bone biopsies of children affected by IJO show alterations in osteoblast activity, with reduced bone formation limited to the trabecular bone, and more specifically to the zones in contact with bone marrow (23). Such data seem to indicate that the skeleton of patients affected by IJO is unable to respond to the greater mechanical requirements of growth and development. Its association with the onset of puberty might also point to a role—not proved until now—of sexual hormones.
The spontaneous resolution of the disease makes it difficult to evaluate treatment efficacy. Positive effects with calcitriol, sodium fluoride or pami-dronate have been reported. Presently, the best choice seems to optimize calcium and vitamin D intake according to the recommended daily allowance, recommend regular physical activity (with low risk of trauma), and avoid excessive loads on spine. Bisphosphonate use should be limited to selected cases with significant pain following repeated vertebral or limb fractures.
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