Sustained beneficial effect of intravenous bisphosphonates after their discontinuation in children

How we approach malignant infantile osteopetrosis

Malignant infantile osteopetrosis (MIOP) is a rare hereditary disorder characterized by excessive bone overgrowth due to a defect in bone marrow resorption by osteoclasts. In most cases, hematopoietic stem cell transplantation (HSCT) may correct bone metabolism but the rapidly progressing nature of this condition necessitates early diagnosis and prompt treatment to minimize irreversible cranial nerve damage. The management of patients with MIOP presents many unique challenges. In this review, the clinical management of patients with MIOP is discussed, including diagnosis, preparation for HSCT and special transplant considerations, management of unique HSCT complications, and long-term follow-up.

Treatment of osteoporosis in children with glucocorticoid-treated diseases

Glucocorticoid induced osteoporosis (GIO) is the most frequent form of drug induced osteoporosis. Glucocorticoids affect osteoblastogenesis, osteoclastogenesis and promote the apoptosis of osteoblasts and osteocytes. A decrease of bone mineral density has been described in several pediatric diseases that require glucocorticoids, both as long-term replacement therapy, such as Congenital Adrenal Hyperplasia, and as treatment of acute phase or relapses, such as asthma, juvenile rheumatoid arthritis, inflammatory bowel diseases, systemic lupus erythematosus, organ transplantation and Steroid Sensitive Nephrotic Syndrome. The increasing number of children with GIO and at risk of fractures reflects the complex nature of this condition, and the need of development of anti-osteoporotic drugs. In this review, we focus on the mechanisms of GIO in some pediatric diseases and on treatment of osteoporosis. We also report data on new signaling pathways as potential targets for future anti-osteoporotic drugs.

The use of bisphosphonates in children: review of the literature and guidelines for dental management

Bisphosphonates are inhibitors of osteoclastic bone resorption with therapeutic benefit in a variety of bone disorders in both adults and children. While these agents have been routinely used in adults for the past three decades, their more recent introduction into paediatric medicine means there is a paucity of data on long-term safety and effects on dental development. There is uncertainty regarding the dental management of children treated with bisphosphonates, particularly when invasive dental procedures, such as extractions and oral surgical procedures, are required. There are limited data with which to make recommendations about the dental management of patients treated with bisphosphonates, and there are no published recommendations that specifically address paediatric patients. This paper aims to outline paediatric uses and adverse effects of bisphosphonates and present recommendations on the dental management of children receiving bisphosphonates.

Bisphosphonates use in children

Bisphosphonates are synthetic analogues of pyrophosphate that inhibit bone resorption by their action on osteoclasts. In recent years, bisphosphonates have been used in children for treatment of a growing number of disorders associated primarily with generalized or localized osteoporosis, genetic and acquired metabolic bone diseases, heterotopic calcifications in soft tissues, and for hypercalcemia. In this review, the authors address the role of and experience with bisphosphonate therapy in disorders of childhood.

Successful use of bisphosphonate and calcimimetic in neonatal severe primary hyperparathyroidism

Neonatal primary hyperparathyroidism (NPHT) is associated with an inactivating homozygous mutation of the calcium sensing receptor (CaSR). The CaSR is expressed most abundantly in the parathyroid glands and the kidney and regulates calcium homeostasis through its ability to modulate parathormone secretion and renal calcium reabsorption. NPHT leads to life threatening hypercalcemia, nephrocalcinosis, bone demineralization, and neurologic disabilities. Surgery is the treatment of choice. While waiting for surgery, bisphosphonates offer a good alternative to deal with hypercalcemia. Cinacalcet is a class II calcimimetic that increases CaSR affinity for calcium, leading to parathormone suppression and increased calcium renal excretion. At present, there is little evidence as to whether cinacalcet could improve the function of mutant CaSR in NPHT. We report a case of NPHT, treated successfully with bisphosphonates and cinacalcet after surgery failure. To our knowledge, it is the first time cinacalcet has been used for NPHT.

Oral Alendronate Treatment for Severe Polyostotic Fibrous Dysplasia due to McCune-Albright Syndrome in a Child: A Case Report

Polyostotic fibrous dysplasia (FD) associated to McCune-Albright Syndrome (MAS) often leads to fractures, deformities, and bone pain resulting in bad quality of life. Parenteral bisphosphonates have been used in children and adolescents to improve these symptoms with few adverse effects. We evaluated the response to oral Alendronate in a girl with severe MAS FD and observed improved quality of life with reduction of bone pain.

Osteoporosis in children: pediatric and pediatric rheumatology perspective: a review

It is increasingly recognized that osteoporosis affects children as well as adults both as a primary problem and as secondary to various diseases, medications, and lifestyle issues. In this review, we emphasize the correct diagnosis of osteoporosis in children as opposed to adults, etiology, and pharmaceutical and non-pharmaceutical treatments. We especially focus on rheumatologic conditions associated with osteoporosis and management issues.

Characterization and management of hypercalcemia following transplantation for osteopetrosis

Autosomal recessive osteopetrosis (OP) is characterized by insufficient osteoclast activity resulting in defective bone resorption and marked increase in skeletal mass and density. OP has been successfully treated with hematopoietic cell transplantation (HCT), secondary to engraftment of donor-derived functioning osteoclasts resulting in remodeling of bone and establishment of normal hematopoiesis. Although hypercalcemia is a common presenting feature of OP, it may be observed following HCT due to engraftment of osteoclasts differentiated from the hematopoietic precursors. To characterize hypercalcemia after HCT-who is at risk, onset, duration and response to treatment-we evaluated 15 patients with OP treated at the University of Minnesota from 2000 to 2009. Hypercalcemia, defined as any single calcium >11.0 mg/100 ml after the first transplant, was found in 40% of patients. Median onset of hypercalcemia was 23 days and the duration was 2-24 days. Hypercalcemia was more common in patients older than 2 years of age at the time of HCT. Treatment with hydration, furosemide and s.c. calcitonin resolved hypercalcemia and resulted in no severe adverse events. In conclusion, hypercalcemia is common in patients with OP within the first 4 weeks after HCT, and more likely in older patients. Isotonic saline, furosemide and s.c. calcitonin were well-tolerated and effective treatments in our study population.

Bisphosphonate-induced osteopetrosis: novel bone modeling defects, metaphyseal osteopenia, and osteosclerosis fractures after drug exposure ceases

In 2003, we reported on a 12-yr-old boy who had developed osteopetrosis (OPT) while receiving pamidronate (PMD) for idiopathic bone pain and enigmatic elevation in circulating bone alkaline phosphatase. Now 17 yr of age, he was re-evaluated 6.5 yr after PMD exposure stopped. Our patient described less bone pain but further limb fractures. His growth plates were fused, yet hyperphosphatasemia persisted. Radiographs documented interval fractures of a metacarpal, an osteosclerotic distal radius, and a dense diaphyseal segment of an ulna where a "chalkstick" break remained incompletely healed after 2 yr. There was new L(4) spondylolysis, and previous L(5) spondylolysis had caused spondylolisthesis. Modeling disturbances of OPT persisted, but partial recovery was shown by metaphyseal surfaces with a unique concave shape. Metaphyseal osteosclerosis had remodeled imperfectly to become focal areas of dense, diaphyseal bone. Newer metaphyseal bone was unexpectedly osteopenic, especially in his distal femurs where cortices were thin and a paucity of trabeculae was documented by CT. Femoral necks had become short and wide with an abnormal contour. A "bone-within-bone" configuration was now present throughout his skeleton. In vertebrae, endplates were thin, and trabecular osteopenia was present central and peripheral to the bands of osteosclerosis. BMD Z-scores assessed by DXA had decreased into the normal range in his spine, hip, and whole body. Iliac crest biopsy showed active bone formation, with much less accumulated primary spongiosa than during the PMD infusions. Osteoclasts that had been dysmorphic, round cells without polarization and off of bone surfaces were now unremarkable in number, location, and appearance. In conclusion, bisphosphonate toxicity during childhood can impair skeletal modeling and remodeling with structural changes that evolve and carry into adult life.

Effects of alendronate and pamidronate on cultured rat metatarsal bones: failure to prevent dexamethasone-induced growth retardation

Bisphosphonates are widely used anti-resorptive drugs in the adult population. In children, their use has mainly been limited to patients with osteogenesis imperfecta. However, the powerful effects of bisphosphonates on bone turnover have raised concern about their long-term effects on the growing skeleton. We aimed to study the effects of two commonly used bisphosphonates, alendronate (Aln) and pamidronate (Pam) on normal bone growth as well as their potential to prevent glucocorticoid-induced growth retardation. Effects on bone growth were studied in fetal rat metatarsal bones (day E20) that were cultured for 5-47 days and measured every 2-7 days. Cellular mechanisms were investigated in metatarsal bones and also in the human chondrocytic cell line HCS-2/8. Chondrocyte viability (WST-1), proliferation (BrdU incorporation), differentiation (collagen type X immunohistochemistry) and apoptosis (TUNEL and Cell Death ELISA) were determined. At a clinically relevant concentration of bisphosphonates (1 microM), metatarsal bone growth was stimulated by both Aln (p<0.001 for length and p<0.05 for width) and Pam (p<0.05 for both length and width) from day 19 of culture. The growth-stimulatory effect was associated with increased chondrocyte proliferation (+21% with Aln and +24% with Pam), while cell differentiation and apoptosis were not affected. Despite the finding that both Aln and Pam (1 muM) rescued HCS-2/8 cells from undergoing dexamethasone-induced apoptosis, neither of them was able to prevent dexamethasone-induced growth retardation of fetal rat metatarsal bones. Aln and Pam have the capacity to stimulate the growth of cultured fetal rat metatarsal bones; an effect associated with increased proliferation of growth plate chondrocytes. Our experimental data suggest that bisphosphonates are ineffective in preventing glucocorticoid-induced growth retardation. Nevertheless, based on our in vitro data, both Aln and Pam appear safe to use in growing children, at least with regard to their effects on linear bone growth.