Osseous complications of pediatric transplantation

Adult and late adolescent complications of pediatric solid organ transplantation

BACKGROUND

There have been over 51 000 pediatric solid organ transplants since 1988 in the United States alone, leading to a growing population of long-term survivors who face complications of childhood organ failure and long-term immunosuppression.

AIMS

This is an educational review of existing literature.

RESULTS

Pediatric solid organ transplant recipients are at increased risk for risk for cardiovascular and kidney disease, skin cancers, and growth problems, though the severity of impact may vary by organ type. Pediatric recipients often are able to complete schooling, maintain a job, and form family and social networks in adulthood, though at somewhat lower rates than the general population, but face additional challenges related to neurocognitive deficits, mental health disorders, and discrimination.

CONCLUSIONS

Transplant centers and research programs should expand their focus to include long-term well-being. Increased collaboration between pediatric and adult transplant specialists will be necessary to better understand and manage long-term complications.

Predictors for pathological bone fractures in children undergoing liver transplantation: A retrospective cohort study

BACKGROUND

Hepatic osteodystrophy refers to bone disorders associated with chronic liver disease, including children undergoing liver transplantation (LT). The aim of this study was to quantify the prevalence of pathological fractures (PF) in children before and after LT and to identify associated factors for their occurrence.

METHODS

Children aged 0-18 years who underwent LT from 1/2005 to 12/2020 were included in this retrospective study. Data on patient demographics, types and anatomical locations of fracture and biological workups were extracted. Variables were assessed at 3 time points: T - 1 at the moment of listing for LT; T0 at the moment of LT and T + 1 at 1-year post-LT.

RESULTS

A total of 105 children (49 [47%] females) were included in this study. Median age at LT was 19 months (range 0-203). Twenty-two patients (21%) experienced 65 PF, 11 children before LT, 10 after LT, and 1 before and after LT. The following variables were observed as associated with PF: At T - 1, low weight and height z-scores, and delayed bone age; at T0, low weight and height z-scores, high total and conjugated bilirubin; at T + 1, persistent low height z-score. Patients in the PF-group were significantly more under calcium supplementation and/or nutritional support at T - 1, T0 and T + 1.

CONCLUSION

More than one in five children needing LT sustain a PF before or after LT. Patients with low weight and height z-scores and delayed bone age are at increased risk for PF. Nutritional support remains important, even if to date it cannot fully counteract the risks of PF.

Promoting bone health in children and adolescents following solid organ transplantation

Solid organ transplantation in children and adolescents provides many benefits through improving critical organ function, including better growth, development, cardiovascular status, and quality of life. Unfortunately, bone status may be adversely affected even when overall status is improving, due to issues with pre-existing bone disease as well as medications and nutritional challenges inherent post-transplantation. For all children and adolescents, bone status entering adulthood is a critical determinant of bone health through adulthood. The overall health and bone status of transplant recipients benefits from attention to regular physical activity, good nutrition, adequate calcium, phosphorous, magnesium and vitamin D intake and avoidance/minimization of soda, extra sodium, and obesity. Many immunosuppressive agents, especially glucocorticoids, can adversely affect bone function and development. Minimizing exposure to "bone-toxic" medications is an important part of promoting bone health in children post-transplantation. Existing guidelines detail how regular monitoring of bone status and biochemical markers can help detect bone abnormalities early and facilitate valuable bone-directed interventions. Attention to calcium and vitamin D supplementation, as well as tapering and withdrawing glucocorticoids as early as possible after transplant, can provide best bone outcomes for these children. Dual-energy X-ray absorptiometry can be useful to detect abnormal bone mass and fracture risk in this population and newer bone assessment methods are being evaluated in children at risk for poor bone outcomes. Newer bone therapies being explored in adults with transplants, particularly bisphosphonates and the RANKL inhibitor denosumab, may offer promise for children with low bone mass post-transplantation.

Pathogenesis and treatment of electrolyte problems post transplant

PURPOSE OF REVIEW

Electrolyte abnormalities posttransplant are common occurrences that can have significant short-term and long-term effects on graft outcome and patient quality of life. Understanding the pathophysiology of these electrolyte derangements can help guide management to optimize bone health and minimize cardiovascular disease. This review explores the pathogenesis of the most common postrenal transplant electrolytes abnormalities as well as current treatment options.

RECENT FINDINGS

Clarifications of the role of FGF-23 has improved our understanding of posttransplant bone disease in addition to the known roles of hyperparathyroidism and vitamin D. The mechanisms of renal electrolyte wasting by immunosuppressive agents give insight into potential treatment options for hyperkalemia and hypomagnesemia.

SUMMARY

Understanding the pathogenesis of the common electrolyte abnormalities found post renal transplant may lead to targeted treatment options that in turn may improve transplant complications. Further studies are required to evaluate the effects on long-term outcomes of renal allografts.

Low bone density and fractures before and after pediatric lung transplantation

INTRODUCTION

Children undergoing lung transplant are at risk for low bone mineral density (BMD) and fractures. The effect of lung transplantation on bone health in pediatric patients is unknown.

MATERIALS AND METHODS

We performed a retrospective chart review of all patients ages 2-21 years who underwent lung transplantation at our hospital from January 2000 to January 2015.

RESULTS

51 patients were studied. At the time of transplant evaluation, BMD Z-score was -2.2 ± 1.4, and 59% of patients had low BMD. BMD Z-score declined in the first year after treatment and returned to near-baseline by the third post-transplant year. Fractures occurred in 9 patients (18%) before and 15 patients (29%) after transplant. Bisphosphonate use was associated with improvement in BMD Z-score and lower mortality risk.

CONCLUSIONS

Pediatric patients had a high prevalence of low BMD at the time of lung transplant evaluation. BMD Z-scores declined in the year after transplant and returned to the pre-transplant level by the third post-transplant year while remaining below normal levels. Fractures were common at sites associated with significant morbidity. These findings support efforts to optimize bone health before and after pediatric lung transplantation, and future studies are needed to evaluate the role of bisphosphonates in these patients.

Bone Disease and Serum Fibroblast Growth Factor-23 Levels in Renal Transplant Recipients

BACKGROUND

Posttransplantation bone disease develops commonly and results in important complications. In this study, we aimed to investigate the relationship between bone diseases and serum fibroblast growth factor-23 (FGF-23) in renal transplant recipients.

METHODS

This study was conducted in 106 kidney transplant recipients (KTrs; group G1) and 30 patients with chronic kidney disease (group G2). Patients with fever, heart failure, angina pectoris, acute renal failure, malignant disease, or any gastrointestinal disease were excluded. KTrs were treated with triple immunosuppressive drugs including glucocorticoids. Complete blood count (CBC), blood urea nitrogen (BUN), creatinine, glomerular filtration rate (GFR, Modification of Diet in Renal Disease [MDRD] formula), lipid profile, calcium (Ca), phosphorous (P), parathormone (PTH), 25OHD3, serum levels of tacrolimus/cyclosporine, and intact FGF-23 were measured. Bone mineral density (BMD) was measured with dual energy X-ray absorptiometry.

RESULTS

The mean patient age was 40.1 ± 11.1 years and 39.2 ± 11.3 years in G1 and G2, respectively (P > .05). In G1 and G2, 76 and 15 patients were male, respectively. Compared with the G2 patients, G1 patients had lower body mass index (BMI), serum glucose levels, P, Mg, and Ca·P (P < .05 for all). T scores of the lumbar vertebrae/femur were -1.82 ± 0.99/-1.34 ± 0.89 and -1.13 ± 1.34/-0.51 ± 1.18 in G1 and G2 patients, respectively (P < .05 for all). The incidences of osteopenia/osteoporosis in the lumbar spine and femur were 50.9%/27.4% and 57.5%/10.4% in G1 and 16.6%/23.3%, and 40%/3.3% in G2. There were positive correlations between BMD and BMI, the time elapsed after renal transplantation, and GFR. In our study, a statistically significant relationship was found between lipid parameters and BMD, PTH, and 250HD3 levels, as well as use of corticosteroid and calcineurin inhibitors (P < .05 for all). In G1 and G2, BMD of the lumbar spine in patients with serum creatinine >1.5 mg/dL was lower than that in patients with serum creatinine <1.5 mg/dL.

CONCLUSION

The association between age and BMD was found only in the femur of KTrs. No relationship was observed between serum FGF-23 levels and BMD values. In both groups, the BMD T score of the lumbar spine was lower compared to the BMD T score of the femur and in patients with serum creatinine >1.5 mg/dL. In long-term follow-up of renal transplantation by as much as 58 months, the incidence of bone disease such as osteoporosis/osteopenia was as high as 67% and was also higher than that of nontransplant patients with similar GFR. In addition to decreased renal function, dyslipidemia, inflammation, and continuing hypophosphatemia were also accompanied by decreased BMD as in cardiovascular disease in KTrs.

Abnormally High and Heterogeneous Bone Matrix Mineralization After Childhood Solid Organ Transplantation: A Complex Pathology of Low Bone Turnover and Local Defects in Mineralization

Chronic renal, liver, and heart failure in children associates with multiple skeletal complications. Increased fracture incidence often persists after transplantation and could be related to alterations in bone material properties. In the present cohort study we evaluated bone mineralization density distribution (BMDD) by quantitative backscattered electron imaging (qBEI) in 23 pediatric solid organ allograft recipients with suspected osteoporosis. We measured BMDD in the entire cross-sectional area of transiliac bone biopsies obtained from kidney (n = 9), liver (n = 9), and heart (n = 5) transplant recipients (aged 7.6 to 19.7 years; 6.0 ± 5.6 years posttransplantation, patients with a history of clinical fractures: n = 14). The BMDD findings were compared with age-appropriate references and with a previously presented cohort of children with chronic kidney disease on dialysis (CKD5D, n = 18). Furthermore, we related the BMDD parameters with patients' clinical and bone histomorphometric outcomes. Compared to healthy children, qBEI results for cancellous and cortical bone in transplant recipients revealed an increase in the most frequently occurring calcium concentration (+2.9%, p = 0.001; +3.5%, p = 0.014), in the portion of fully mineralized bone (fivefold; 10-fold, both p < 0.0001) and in heterogeneity of mineralization (+26,5% and +27.8%, both p < 0.0001), respectively. Moreover, the BMDD parameters were nonsignificantly distinct from CKD5D cohort except that the heterogeneity in mineralization was higher posttransplantation. There was a strong inverse correlation between the average calcium content of the bone matrix and patients' biochemical ALP levels, histomorphometric indices of bone formation and resorption. The abnormally high bone matrix mineralization in transplant recipients, consistent with serum and histomorphometric outcomes, suggests a history of low bone turnover with accumulation of fully mineralized bone packets. Additionally, the increased heterogeneity of mineralization suggests local alterations in mineralization kinetics, which may be linked to dysfunctional osteocytes that were recently shown to accumulate within the bone matrix during organ failure and concomitant glucocorticoid and immunosuppressive medication. © 2017 American Society for Bone and Mineral Research.

The evaluation of bone metabolism in children with renal transplantation

This study aims to evaluate BMD and bone biomarkers and to investigate the effects of immunosuppressives on bone disease after RTx. Thirty-three RTR aged 16.7 ± 3.7 yr and healthy controls (n = 32) were enrolled. There was no difference between pre-RTx BMD and BMD at the time of study (45.9 ± 30.9 months after RTx), while both values were lower than controls (p < 0.01 and p < 0.05, respectively). Worst BMD scores were obtained at sixth month after RTx (-0.2 ± 0.9) and best at fourth year (1.4 ± 1.3). 25-hydroxy-(OH) vitamin D and OPG were higher in RTR (p < 0.001). BMD z scores negatively correlated with OPG and cumulative CS doses at the time of study (r = -0.344, p < 0.05 and r = -0.371, p < 0.05, respectively). Regression analysis revealed OPG as the only predictor of BMD (β -0.78, 95% CI -0.004 to -0.013, p < 0.001). The increase in OPG, a significant predictor of BMD, could either be secondary to graft dysfunction or for protection against bone loss. CS doses should be minimized to avoid their untoward effects on bone metabolism.

Vitamin D deficiency and insufficiency after pediatric liver transplantation

Vitamin D deficiency and insufficiency are increasingly recognized in the general population, including healthy children. There is also an increasing emphasis on the importance of vitamin D status following pediatric liver transplantation and specifically its relationship to metabolic bone disease and growth retardation. Vitamin D insufficiency has also been associated with multiple immunological and metabolic disorders in adults. To our knowledge, this has not been systematically evaluated in children undergoing liver transplantation to date. Between October 2004 and August 2008, serum 25-(OH)-vitamin D levels were measured in 199 children who had undergone liver transplantation at Birmingham Children's Hospital. Potential factors contributing to vitamin D levels were evaluated. Additionally, we evaluated a possible relationship between vitamin D levels and immunological phenomena and metabolic complications. Median 25-(OH)-vitamin D level was 19.5 ng/mL (range: 4.4-71.4 ng/mL). A total of 105 children (53%) had insufficient vitamin D levels and 28 children (14%) showed vitamin D deficiency. The only factors found to be associated with vitamin D deficiency were season of sample, ethnicity, and PTH levels. Vitamin D deficiency was more prevalent during the first year after transplantation. We did not find a significant relationship between vitamin D levels and graft function or any other immunological and metabolic complications. Vitamin D insufficiency and deficiency are common in children after liver transplantation, especially in winter and spring and in non-white patients. Initial post-transplant period and high PTH are significantly associated with vitamin D deficiency. Vitamin D status should be monitored following pediatric liver transplantation and vitamin D supplementation provided as required.

Solid-organ transplantation in childhood: transitioning to adult health care

Pediatric solid-organ transplantation is an increasingly successful treatment for solid-organ failure. With dramatic improvements in patient survival rates over the last several decades, there has been a corresponding emergence of complications attributable to pretransplant factors, transplantation itself, and the management of transplantation with effective immunosuppression. The predominant solid-organ transplantation sequelae are medical and psychosocial. These sequelae have a substantial effect on transition to adult care; as such, hurdles to successful transition of care arise from the patients, their families, and pediatric and adult health care providers. Crucial to successful transitioning is the ongoing development of a sense of autonomy and responsibility for one's own care. In this article we address the barriers to transitioning that occur with long-term survival in pediatric solid-organ transplantation. Although a particular transitioning model is not promoted, practical tools and strategies that contribute to successful transitioning of pediatric patients who have received a transplant are suggested.

Nonimmune complications after transplantation

As posttransplant longevity has increased, nonimmune complications related to the transplant and posttransplant course have emerged as important factors in defining long-term outcomes. The incidence of, and risk factors for these complications may vary by transplanted organ based on immunosuppressive protocols and preexisting risk factors. This article discusses the relevant nonimmune complications associated with posttransplant care, with a focus on risk factors and management strategies.

Adverse effects of immunosuppression in pediatric solid organ transplantation

Solid organ transplantation is a life-saving treatment for end-stage organ failure in children. Immunosuppressant medications are used to prevent rejection of the organ transplant. However, these medications are associated with significant adverse effects that impact growth and development, quality of life (QOL), and sometimes long-term survival after transplantation. Adverse effects can differ between the immunosuppressants, but many result from the overall state of immunosuppression. Strategies to manage immunosuppressant adverse effects often involve minimizing exposure to the drugs while balancing the risk for rejection. Early recognition of immunosuppressant adverse effects may help to reduce morbidities associated with solid organ transplantation, improve QOL, and possibly increase overall patient survival.

Post-renal transplantation hypophosphatemia

An understanding of the pathophysiologic mechanisms of post-renal transplant (PRT) bone disease is of important clinical significance. Although bone disease occurs after all solid organ transplantation, the cumulative skeletal fracture rate remains high in PRT subjects while reaching a plateau with other transplantations. One major difference in the pathophysiology of PRT bone disease is, perhaps, due to persistent renal phosphorus (Pi) wasting. Novel phosphaturic agents have recently been suggested to participate in the development of bone disease in PRT subjects. However, it is unclear as of yet whether these factors alone or in conjunction with excess parathyroid hormone (PTH) secretion play a key role in the development of negative Pi balance and consequent bone disease in this population. In this review, I present a natural history of PRT hypophosphatemia and persistent renal Pi leak, provide pathophysiologic insight into these developments, and discuss the difficulty in diagnosing these phenotypes in both adult and pediatric populations.

Limitations of dual x-ray absorptiometry in children with chronic kidney disease

Dual x-ray absorptiometry (DXA) is the most widely used densitometric method for diagnosing osteoporosis in adults. It has also been widely adopted as a diagnostic tool in the pediatric population. The most significant limitation of DXA is its reliance on areal rather than volumetric bone mineral density (BMD), which results in an artificial underestimation of bone density in short people. Poor longitudinal growth, however, is an eminent problem in children with chronic kidney disease (CKD). There is also no evidence in children that areal BMD is predictive of future fracture risk, which is the traditional rationale for measuring BMD in children with CKD. Therefore, the Kidney Disease Outcomes Quality Initiative guidelines and the current position of the International Society for Clinical Densitometry (ISCD) on pediatric patients, both of which are presented in this issue of Pediatric Nephrology, do not recommend the use of DXA in children with CKD. To date, there is no consensus on the best method to assess the degree of renal osteodystrophy in this patient population, and further collaborative efforts to correlate densitometric findings with clinical outcomes are warranted.

Calcineurin inhibitor sparing in paediatric solid organ transplantation : managing the efficacy/toxicity conundrum

Despite their efficacy, the calcineurin inhibitors (CNIs) ciclosporin and tacrolimus carry a risk of debilitating adverse effects, especially nephrotoxicity, that affect the long-term outcome and survival of children who are given organ transplants. Simple reduction in dosage of CNI has little or no long-term benefit on their adverse effects, and complete withdrawal without threatening graft outcome may only be possible after liver transplantation. Until the last decade, the only option was to increase corticosteroid and/or azathioprine doses, which imposed additional long-term hazards. Considered here are the emerging generation of new agents offering an opportunity for improving long-term graft survival, minimizing CNI-related adverse events and ensuring patient well-being.A holistic, multifaceted strategy may need to be considered - initial selection and optimized use and monitoring of immunosuppressant regimens, early recognition of indicators of patient and graft dysfunction, and, where applicable, early introduction of CNI-sparing regimens facilitating CNI withdrawal. The evidence reviewed here supports these approaches but remains far from definitive in paediatric solid organ transplantation. Because de novo immunosuppression uses CNI in more than 93% of patients, reduction of CNI-related adverse effects has focused on CNI sparing or withdrawal.A recurring theme where sirolimus and mycophenolate mofetil have been used for this purpose is the importance of their early introduction to limit CNI damage and provide long-term benefit: for example, long-term renal function critically reflects that at 1 year post-transplant. While mycophenolic acid shows advantages over sirolimus in preserving renal function because the latter is associated with proteinuria, sirolimus appears the more potent immunosuppressant but also impairs early wound healing. The use of CNI-free immunosuppressant regimens with depleting or non-depleting antibodies plus sirolimus and mycophenolic acid needs much wider investigation to achieve acceptable rejection rates and conserve renal function. The adverse effects of the alternative immunosuppressants, particularly the dyslipidaemia associated with sirolimus, needs to be minimized to avoid replacing one set of adverse effects (from CNIs) with another. While we can only conjecture that judicious combinations with the second generation of novel immunosuppressants currently in development will provide these solutions, a rationale of low-dose therapy with multiple immunosuppressants acting by complementary mechanisms seems to hold the promise for efficacy with minimal toxicity until the vision of tolerance achieves reality.

Therapy Insight: orthopedic complications after solid organ transplantation in childhood

Several factors, such as immobilization, metabolic bone disease and immunosuppressive drugs, can compromise the quality of bone in children who have undergone solid organ transplantation. In contrast to adults, decreased bone mineral density has been reported in only a small proportion of pediatric transplant patients, and the relationship between low bone mineral density and fracture risk has not been established in children. Nevertheless, fractures, scoliosis, and joint and spinal degeneration are common in patients who received solid organ grafts as children. Avascular bone necrosis occurs infrequently in this patient population. Future studies should evaluate the effects of the underlying disease, transplantation and immunosuppression on the metabolism of bone and cartilage. On the basis of our own clinical experience and literature review, the growing spine of children who have received transplants should be continuously evaluated, and follow-up of bone mineral density is indicated. By contrast, routine MRI of the joints seems unnecessary.

Immunosuppression in pediatric solid organ transplantation: opportunities, risks, and management

The pediatric transplant community stands at a time of unprecedented choice of immunosuppressive agents - and with a legacy of morbidity from those agents used in the previous two decades. This review considers the clinical utility and side-effect profiles of immunosuppressants used widely in current practice (e.g., glucocorticoids, azathioprine, ciclosporin, tacrolimus, mycophenolate, and sirolimus) and those agents which are in increasing use or in evaluation (e.g., IL-2 receptor antibodies, everolimus, FTY720, LEA29Y, and deoxyspergualin). Further consideration is given to the wider drug interactions likely during the use of new immunosuppressant regimens and to our growing awareness of the influences of genetic heterogeneity on drug efficacy and handling. Finally, we consider the new demands being placed on the use of drug monitoring to regulate dosage of this new repertoire of immunosuppressants.