Should pediatric idiopathic hypercalciuria be treated with hypocalciuric agents?

Bone Metabolism Defects in Children With Idiopathic Hypercalciuria: An Update

Idiopathic hypercalciuria (IH) in adults is considered to be the most common identifiable metabolic risk factor for calcium nephrolithiasis, also contributing to osteopenia and osteoporosis. Data on children and adolescents associating IH with bone metabolism show that up to one-third of such patients present with lower bone mineral density (BMD), increasing the risk of osteopenia, osteoporosis, and bone fractures in adulthood. Several factors, such as the degree of hypercalciuria and the presence of calcium urolithiasis, seem to affect the severity of bone metabolism abnormalities in children with IH. In order to follow these patients, BMD has traditionally been estimated by dual-energy X-ray absorptiometry (DXA) scan. In children, chronological age should be taken into account when measuring BMD, as well as weight, height, and BMI. In addition, biochemical bone turnover markers provide surrogate indices of bone turnover and complement the static measurements of BMD. They respond rapidly to changes in bone physiology, and their measurement can be repeated more frequently. However, since children's bone mass increases constantly until after puberty, age, sex, and pubertal stage have to be taken into consideration when assessing these markers. In addition, relevant studies in children and adolescents have shown conflicting results. Regarding the management of patients with IH, identification and appropriate treatment are of great importance in order to prevent the formation of kidney stones, as well as to improve bone metabolism defects and decrease fracture risk. Such treatment measures include dietary interventions, potassium citrate supplementation and/or thiazide diuretics, and bisphosphonates in resistant cases. This review summarizes the latest data on bone metabolism defects in children and adolescents with IH, the possible pathomechanisms involved, the biochemical markers that could be used together with DXA to follow these patients, and the available treatment options.

Rickets guidance: part II-management

Here, we discuss the management of different forms of rickets, including new therapeutic approaches based on recent guidelines. Management includes close monitoring of growth, the degree of leg bowing, bone pain, serum phosphate, calcium, alkaline phosphatase as a surrogate marker of osteoblast activity and thus degree of rickets, parathyroid hormone, 25-hydroxyvitamin D₃, and calciuria. An adequate calcium intake and normal 25-hydroxyvitamin D₃ levels should be assured in all patients. Children with calcipenic rickets require the supplementation or pharmacological treatment with native or active vitamin D depending on the underlying pathophysiology. Treatment of phosphopenic rickets depends on the underlying pathophysiology. Fibroblast-growth factor 23 (FGF23)-associated hypophosphatemic rickets was historically treated with frequent doses of oral phosphate salts in combination with active vitamin D, whereas tumor-induced osteomalacia (TIO) should primarily undergo tumor resection, if possible. Burosumab, a fully humanized FGF23-antibody, was recently approved for treatment of X-linked hypophosphatemia (XLH) and TIO and shown to be superior for treatment of XLH compared to conventional treatment. Forms of hypophosphatemic rickets independent of FGF23 due to genetic defects of renal tubular phosphate reabsorption are treated with oral phosphate only, since they are associated with excessive 1,25-dihydroxyvitamin D production. Finally, forms of hypophosphatemic rickets caused by Fanconi syndrome, such as nephropathic cystinosis and Dent disease require disease-specific treatment in addition to phosphate supplements and active vitamin D. Adjustment of medication should be done with consideration of treatment-associated side effects, including diarrhea, gastrointestinal discomfort, hypercalciuria, secondary hyperparathyroidism, and development of nephrocalcinosis or nephrolithiasis.