Bone mineral deficits in recipients of hematopoietic cell transplantation: the impact of young age at transplant.

Low bone mineral density (BMD) has been reported in recipients of pediatric hematopoietic cell transplantation (HCT), but it is unclear whether age at HCT has a role. The objective of this cross-sectional study was to determine if patients treated with HCT before the age of 10 years have long-term BMD deficits compared with patients transplanted at an older age and with sibling controls. The study included 151 HCT recipients (87 males), age at study 24.7±8.6 years treated with HCT for hematologic malignancies at age 10.9±6.4 years, and 92 healthy sibling controls (49 males), age at study 22.3±8.0 years. Dual-energy x-ray absorptiometry was performed to measure BMD Z-scores for total body BMD (TBMD), lumbar spine BMD (LBMD) and femoral neck BMD (FNBMD, for subjects 20 years at study visit). Patients <10 years at HCT had significantly lower TBMD and FNBMD Z-scores (by 0.5 and 0.8 s.d., respectively) compared with controls (P=0.003 and P=0.0001, respectively) and patients >18 years at HCT (P=0.04 and P=0.004, respectively) at an average of 14 years after HCT. In conclusion, this study identified young age at transplant as an important risk factor for bone deficits in young adulthood, suggesting that efforts to reduce bone loss should focus on this patient population.

Changes in biomarkers of bone resorption over the first six months after pediatric hematopoietic cell transplantation.

Bone loss has been observed within the first six months after HCT in both children and adults. While there is some evidence that bone formation may be reduced in children after HCT, it is currently unknown whether bone resorption is increased. The objective of this prospective study was to evaluate changes in markers of bone resorption over the first six months after pediatric HCT. Twenty-six participants (eight females) aged 10.9 ± 3.4 yr entered the study prior to HCT. Bone resorption was measured by urine DPD and PYD, and by plasma NTX and CTX. Seventeen participants who completed day +30 visit and either day +100 or +180 visits were included in the analysis. DPD increased between days +30 and +100 (mean change, 11.3 nmol/nmol creatinine; p = 0.012) and between days +30 and +180 (13.7 nmol/nmol creatinine; p = 0.036). PYD increased between days +30 and +100 (32 nmBCE/L; p = 0.019). CTX increased between baseline and day +100 (5.9 µg/L; p = 0.012). Changes in NTX levels were not statistically significant. This study shows that markers of bone resorption increase in children after HCT, suggesting that increased resorption may be a contributing factor to the pathophysiology of bone loss after pediatric HCT.

Screening, prevention and management of osteoporosis and bone loss in adult and pediatric hematopoietic cell transplant recipients.

Long-term survivors of hematopoietic cell transplantation (HCT) are at risk for loss of bone mineral density (BMD) and subsequent osteoporosis. There is a lack of clear guidelines for the screening, prevention and treatment of bone loss after HCT. We reviewed the prevailing literature and provide guidelines developed by our center for the screening and management of this complication. Bone loss occurs predominantly within the first 6-12 months after autologous and allogeneic HCT. Recovery first occurs in the lumbar spine and is followed by a slower recovery of BMD in the femoral neck. BMD may not return to baseline levels in patients with continuing exposure to corticosteroids and calcineurin inhibitors. All HCT recipients should be advised general interventions to reduce fracture risk including adequate intake of calcium and vitamin D. We recommend screening all adult allogeneic and autologous HCT recipients with dual-energy X-ray absorptiometry 1 year after transplantation. Patients at high risk for bone loss (for example, patients receiving ≥ 5 mg of prednisone equivalent daily for > 3 months) can be screened earlier (for example, 3-6 months after HCT). Where indicated, bisphosphonates or other anti-resorptive agents (for example, calcitonin) can be used for prevention or treatment of osteoporosis in adult HCT recipients. Pediatric HCT recipients should be referred to a pediatric endocrinologist for evaluation and treatment of bone loss. There remain several areas of uncertainty that need further research in adult and pediatric HCT recipients, such as the optimal timing and frequency of screening for loss of bone mineral density, relationship of bone loss with risk of fractures, selection of appropriate patients for pharmacologic therapy, and optimal dosing schedule and duration of therapy with anti-resorptive agents.

Growth patterns and the use of growth hormone in the mucopolysaccharidoses.

Short stature is characteristic of patients with mucopolysaccharidosis (MPS) diseases. For children with skeletal dysplasias, such as MPS, it is important to know the natural history of growth. An understanding of the natural growth pattern in each MPS disease provides a measurement to which treatments can be compared, as well as data which can help families and providers make individualized decisions about growth promoting treatments. Multiple advancements have been made in the treatment of MPS with both hematopoietic cell transplantation (HCT) and enzyme replacement therapy (ERT). The long term benefit of these treatments on growth is unknown. This article will review the published data on growth in children with MPS, and describe preliminary data on the use of human growth hormone (hGH) in children with MPS.

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.

Short-term growth hormone treatment in children with Hurler syndrome after hematopoietic cell transplantation.

Children with Hurler syndrome experience progressive growth failure after hematopoietic cell transplantation (HCT). The goal of this study was to review the safety and efficacy of growth hormone (GH) in eight children with Hurler syndrome who were treated at our institution with GH for short stature or GH deficiency between 2005 and 2008. The age at initiation of treatment with GH was 9.6+/-2.3 years and time since HCT was 7.5+/-1.5 years. Mean GH dose was 0.32 mg/kg/week. Baseline growth velocity was 3.5+/-1.5 cm/year (-2.6+/-1.9 s.d.), and it increased to 5.2+/-3.0 cm/year (-0.1+/-3.6 s.d.) after 1 year of treatment. Of the six patients with radiographic data, there was one progression of scoliosis, one progression of kyphosis and one progression of genu valgum. No patient discontinued treatment due to progression of skeletal disease. One patient discontinued GH due to slipped capital femoral epiphysis. Preliminary data suggest that 1-year GH treatment may modestly improve growth velocity in children with Hurler syndrome.

Growth and endocrine function in patients with Hurler syndrome after hematopoietic stem cell transplantation.

Short stature is characteristic of Hurler syndrome, or mucopolysaccharidosis type IH (MPS IH). Hematopoietic stem cell transplantation (HSCT) is used to treat children with MPS IH. While HSCT corrects some of the metabolic features of MPS IH, its effects on growth are not well delineated. We investigated growth in patients with MPS IH after HSCT and described accompanying endocrine abnormalities. A cohort of 48 patients with MPS IH who had received HSCT between 1983 and 2005 were included. The prevalence of short stature (height <-2 s.d. score, SDS) before HSCT was 9%, and increased to 71% at last follow-up (6.9+/-5.1 years after HSCT). Short stature was positively associated with increased age at HSCT (P=0.002) and TBI (P=0.009). In total, 23% had growth hormone deficiency and/or low insulin-like growth factor-1, one female patient had premature adrenarche, one precocious puberty and 27% had clinical or subclinical hypothyroidism. Growth failure is highly prevalent in children with MPS IH after HSCT. Children who had no TBI exposure and were younger at the time of HSCT had a better height outcome.