Determination of bone mass in idiopathic juvenile osteoporosis

Idiopathic juvenile osteoporosis (IJO) is the rare metabolic disorder with dynamic evolution and spontaneous recovery. The disease appears in previously healthy children and causes permanent bone deformations. Etiology of IJO remains unknown. The diagnosis is established through exclusion of known causes of osteoporosis. The goal of this study is the estimation of the bone mass determinants in the acute and chronic phases of IJO. We carried out a retrospective analysis of 41 children with recognised IJO, and 13 young adults who have had IJO for years. IJO was diagnosed according to C. Dent's criteria. The known causes of osteoporosis were excluded. The typical clinical symptoms included fractures, pain in the ankle and back, pathological gait pattern, decreased muscular strength, height loss and stature deformations. The main radiological features were generalized osteopenia, fractures in the long bones, metaphyseal compression fractures and collapsed biconcave vertebrae. According to clinical state, acute and chronic phases of IJO were excluded. Biochemistry was normal for age except for urine calcium, pyridinoline and deoxypyridinoline levels. These parameters were elevated at the onset of the disease. DEXA measurements of total body bone mineral density (TBBMD) were carried out with the use of Lunar DPX-L apparatus. The results were expressed as a Z-score. The densitometric issues demonstrated a significant bone mass decrease in the acute phase of the IJO. The calcaneus bone was measured with ultrasound Achilles bone densitometer. A system of special pads positioning the foot, and narrowed ultrasound beam were used for pediatric adoption. We noted "decreased stiffness" parameter in boys and girls with the acute phase of IJO, compared with the values of healthy children. We examined young adults who have had IJO and measured their TBBMD. Mean Z-score persisted below -1 SD compared with age-matched controls.