The renal bone diseases in children treated with dialysis

Uremic Leontiasis Ossea: Theoretical Concepts and Practical Considerations

Leontiasis ossea (LO) in chronic kidney disease patients, also known as Sagliker syndrome, is an exceptionally uncommon uremic complication of long-lasting and severe secondary hyperparathyroidism. The prominent features of uremic LO (ULO) encompass the characteristic clinical trial of massive thickening of maxillary and mandibular bones, widening of interdental spaces, and flattening of nasal bridges and nares. Moreover, during the transformation of craniofacial architecture, significant structural and functional consequences may appear, including upper airway patency, visual and hearing acuity, oral phase of swallowing as well as various neurological and psychiatric disorders. Only few cases of ULO have been reported in the literature until now, making challenging not only the traditional diagnostic procedures but also the optimal therapeutic approach. In this narrative review, we aim to explore the underlying pathophysiological mechanisms, summarize the evidence for adverse outcomes, and highlight the current therapeutic strategies for ULO prevention and treatment, given that precise genetic determinants remain elusive.

Serum fetuin-A and vitamin D in children with mild-to-severe chronic kidney disease: a cross-sectional study

BACKGROUND

Fetuin-A and vitamin D are significant correlates of cardiovascular morbidity in paediatric chronic kidney disease (CKD) patients. It is thus far unknown, whether or not serum fetuin-A is affected by the vitamin D status or treatment with vitamin D preparations in these patients.

METHODS

In a cross-sectional study, serum concentrations of fetuin-A, 25-hydroxyvitamin D(3) (25OHD) and 1,25-dihydroxyvitamin D(3) (calcitriol) levels were determined in 112 paediatric patients with mild-to-severe CKD (Stages 1-5) and after renal transplantation. A25OHD supplementation and/or calcitriol treatment were given in 64% of the patients.

RESULTS

Fetuin-A levels were clearly reduced in dialysis patients but were comparable to healthy controls in those with moderate CKD and after transplantation. Although 64 and 46% of all patients received 25OHD and/or calcitriol treatment, 48 and 20% of patients were 25OHD and/or calcitriol deficient, respectively. Within the whole patient cohort, fetuin-A correlated with serum calcium and yearly weight-related 25OHD dosage (each P < 0.01) but not with the vitamin D status per se. Multiple regression analysis revealed the need for dialysis treatment and cumulative 25OHD dosage as independent predictors of fetuin-A concentrations (model r(2) = 0.17). In dialysis patients, fetuin-A was inversely correlated with serum C-reactive protein but positively correlated with cumulative calcitriol dosage and serum parathormone (each P < 0.01).

CONCLUSIONS

Fetuin-A levels are clearly reduced in children on dialysis but not in those with moderate CKD and after transplantation. Besides the degree of microinflammation, the cumulative intake of 25OHD and calcitriol are significantly correlated to fetuin-A in these patients. The impact of vitamin D treatment appears to be at least partly mediated by serum calcium.

Vitamin D deficiency and toxicity in chronic kidney disease: in search of the therapeutic window

Both vitamin D deficiency and vitamin D toxicity are associated with cardiovascular complications in chronic kidney disease (CKD). Clinical and experiment data indicate that the association of vitamin D levels with cardiovascular disease is best illustrated as a biphasic, or U-shaped, curve. Children and adolescents with CKD need vitamin D due to the demands of a growing skeleton, to prevent renal rickets. However, this therapy carries the risk of severe side effects and chronic toxicity. Observational studies show that vitamin D deficiency and toxicity are frequently present in patients with CKD. In view of the importance of cardiovascular complications for the long-term survival of young patients, these findings demand a judicious use of vitamin D preparations. In clinical practice, the therapeutic window is rather small, presenting a therapeutic challenge to avoid both vitamin D deficiency and toxicity.

Cinacalcet is efficacious in pediatric dialysis patients

Secondary hyperparathyroidism (high-turnover bone disease, or HTBD) is manifested by elevated parathyroid hormone (PTH) levels. Control of HTBD may be achieved by maintaining low serum phosphorous levels and administering vitamin D therapy, although some patients continue to exhibit high PTH levels. We report the results of the efficacy of the calcimimetic cinacalcet in six hemodialysis (HD) and three peritoneal dialysis (PD) pediatric patients with HTBD, age 14.5 +/- 1.0 (range 7.5-17.5) years. Six patients received 30 mg/day, one required 60 mg/day, and two received 120 mg/day. Treatment with cinacalcet resulted in a 61% decline in intact PTH (iPTH) levels (1,070 +/- 171.5 pretreatment to 417.6 +/- 97.8 posttreatment pg/ml, p = 0.005). Serum alkaline phosphatase also declined (561.8 +/- 169.6 U/L pretreatment to 390.3 +/- 110.3 U/L posttreatment pg/ml). During therapy, serum calcium (p = 0.9) and phosphorous (p = 0.9) levels, calcium-phosphorous product (p = 0.8), systolic blood pressure (BP) (p = 1.0), diastolic BP (p = 0.8), and hemoglobin (p = 0.9) remained unchanged. The dose of oral calcitriol for the three patients on PD while receiving cinacalcet trended downward (0.8 +/- 0.2 pretreatment vs. 0.5 +/- 0.0 microg/day posttreatment pg/ml), as did the dose of paracalcitol for those receiving HD (6.6 +/- 2.3 pretreatment vs. 4.3 +/- 1.7 micrograms/day posttreatment pg/ml). We conclude that short-term treatment with the calcimimetic cinacalcet is efficacious in adolescent dialysis patients.

Preservation of bone mass in pediatric dialysis and transplant patients

Renal osteodystrophy continues to be a major challenge to the physician treating the child with end-stage renal disease (ESRD). The gold standard for the assessment of bone status is bone histomorphometry, which divides bone pathology into 3 main types; high-turnover, low-turnover, and mixed disease. The high-turnover disease, related to hyperparathyroidism, has been the one most extensively investigated; however, optimal therapy, especially in the growing child, is yet unclear. Overzealous treatment might result in adynamic bone disease (an extreme example of low-turnover disease), and further interference with statural growth. Pre-existent bone disease after kidney transplantation seems to worsen immediately, probably because of the high dose of corticosteroids used. In children who attain normal kidney function in the allograft, bone status seems to improve over time. Little is known about bone in transplanted patients with reduced glomerular filtration rate (GFR). The correlation between bone histology and its main surrogates, bone remodeling markers and bone mineral density, is yet unclear, but it might serve to follow the progress of an individual patient. New therapeutic modalities aimed at suppressing hyperparathyroidism, and consequently bone resorption, as well as agents directly attenuating bone resorption, should be further investigated for their effect on bone in patients with ESRD or after transplantation. Similarly, agents stimulating bone formation, particularly growth hormone, require further attention for their potential to improve bone status. Bone health and the child's somatic growth at ESRD or after kidney transplantation are closely related, and therapy should be aimed at achieving optimal results for both.

Spectrum of renal osteodystrophy in children on continuous ambulatory peritoneal dialysis

BACKGROUND

The prevalence of different types of bone disease in chronic renal failure (CRF) has changed significantly during the last decade. The aim of the present study is to evaluate the spectrum of bone disease in children with CRF undergoing continuous ambulatory peritoneal dialysis (CAPD).

METHODS

Seventeen children with CRF on CAPD aged 7-20 years were evaluated. All patients had received regular vitamin D and calcium carbonate therapy during the 6 months preceding the bone biopsy. Serum calcium, phosphate, alkaline phosphatase and immunoreactive parathyroid hormone (iPTH) levels were measured and hand X-rays were performed. Transiliac bone biopsies were analyzed for histologic diagnosis.

RESULTS

High turnover renal osteodystrophy (ROD) was the most common bone disease, present in eight patients (47%). Five patients (29%) had low turnover bone disease, and four (24%) had mixed ROD. The mean age of the high turnover ROD group was higher than that of the low turnover group (14 +/- 3 vs. 11 +/- 3 years, P < 0.05). Seven of the nine patients who had tubulo-interstitial nephritis were found to have high turnover bone disease. In contrast, none of the patients with glomerulonephritis exhibited high turnover bone lesions. Mean serum calcium levels were found to be significantly higher in the low turnover group compared with the patients with high turnover bone disease (P < 0.001). A serum iPTH level > 200 pg/mL was 100% sensitive and 66% specific in identifying patients with high turnover ROD.

CONCLUSION

The spectrum of bone disease of the children with CRF undergoing CAPD seems to depend on the rate of CRF and primary disease. The risk of developing overt hyperparathyroid bone disease is high in children with slowly progressing forms of renal pathology and especially in those with tubulo-interstitial disease. In contrast, children with glomerular diseases who had a more rapidly progressive course may have a lesser risk of developing high turnover bone disease. The results of the present study indicate that even routinely prescribed regular vitamin D therapy early in the course of disease may lead to low turnover bone lesion in small children who have CRF due to rapidly progressive forms of renal pathology.