The study protocol was approved by the ethics committee of Jichi Medical University.
The records of children treated at the Jichi pediatric university hospital from September 2007 to September 2012 were analyzed retrospectively. Sixteen children with ISSNS (12 boys and 4 girls, median age 5.5 years, range 1 - 13 years), and 13 with IgAN (6 boys and 7 girls, median age 12 years, range 8 - 15 years) were included in this study. The ISSNS patients were all in their first onset. The definition of NS according to the international study of kidney disease in children (ISKDC) criteria is as follows: Proteinuria > 40 mg/m2 per hour and hypoalbuminemia < 2.5 g/dL. The diagnosis of ISSNS was made when remission of NS was achieved within four weeks of initiation of STx. The IgAN patients had not received any prior GC treatments. IgAN was defined by the presence of diffuse dominant or codominant mesangial deposits of immunoglobulin A (IgA), with mesangial cellular proliferation in renal tissue.
The ISSNS patients were treated with prednisolone (2 mg/kg per day, maximum 60 mg per day) in three divided doses for four weeks, followed by 1.3 mg/kg in one single-morning dose on alternate days for another four weeks. Then prednisolone was terminated eight weeks after STx initiation. Steroid-dependent and steroid-resistant patients were excluded from the study. None of the patients received immunosuppressive agents, or any drugs that influenced bone strength such as Ca, vitamin D, and alendronate.
The IgAN patients underwent tonsillectomy followed by three courses of steroid pulse therapy. Each course consisted of methylprednisolone (20 mg/kg, maximum 500 mg) per dose on three consecutive days per week, followed by prednisolone (1 mg/kg per day, max 30 mg per day). They were then treated with prednisolone (1 mg/kg) every other day for 4 - 9 months (median 5 months) until they reached a remission phase and were negative for proteinuria and hematuria.
We evaluated bone strength by BMD scores and S-ALP levels. In the ISSNS group, BMD scores and S-ALP levels were examined in Phase 0 before the initiation of STx; in Phase 1 one month after the initiation of STx; and in Phase 2 one month later after terminating STx, that is, two months after the initiation of STx. The BMD of the lumbar spine (L2 - L4) was measured using dual-energy x-ray absorptiometry scans (The Discovery A, Hologic, USA). In the IgAN group, the BMD scores and S-ALP levels were examined as follows: Phase 0, before the initiation of STx, in Phases 1, 2, and 3 at one, three and six months, respectively, after the initiation of STx and in Phases 4, 12 months after the initiation of STx (10 months after tapering of STx). The patients had no restrictions on physical education. The variation of bone strength was evaluated by comparing pre-treatment BMD scores and S-ALP levels with those at each month.
Statistical analyses were performed using JMP Software 8 (SAS Institute Inc. USA). Paired t-test was used for comparisons. Results are presented as the mean ± SE, and a P value of less than 0.05 was considered statistically significant.
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