Diagnosis of renal osteodystrophy

Brown Tumors Belong to the Spectrum of KRAS -driven Neoplasms

Brown tumors are rare and generally self-limiting mass lesions of bone occurring in the context of hyperparathyroidism. Although commonly regarded as endocrine-driven tumor-like lesions, we detected pathogenic hotspot KRAS mutations in 10/16 brown tumors (62%) with similar frequencies found in cases affecting the peripheral and axial skeleton. Pathogenic mutations in other driver genes of the RAS-MAPK pathway were not identified. Our findings suggest brown tumors to represent true neoplasms driven by the activation of the RAS-MAPK signaling pathway. The frequent regression of brown tumors after normalization of hyperparathyroidism points to a second hit mediated by endocrine stimulation to be required for tumor development. Our findings underline the pathogenic relation of brown tumors to nonossifying fibroma and giant cell granuloma of the jaws which both appear histologically similar to brown tumors and are also driven by RAS-MAPK signaling pathway activation.

Correction of Severe Knees Valgus Deformities in a Patient With Renal Osteodystrophy

Renal osteodystrophy (ROD) is a complex and rare entity that refers to a large spectrum of abnormalities of skeletal homeostasis in patients suffering from chronic kidney disease. The goal of this study was to present the outcome of the very rare case of an adult with severe deformity of painful bilateral valgus knees due to ROD, requiring multilevel osteotomies above and below the knee. A 42-year-old male patient was admitted to our department with painful severe bilateral valgus knees deformity due to ROD. The patient underwent bilateral lateral opening-wedge osteotomy of distal femur and medial tibial closing-wedge osteotomy. The osteotomies site healed in 8 weeks without complications. The surgical treatment of lower limb valgus knee deformities secondary to ROD is a challenging and demanding procedure. In our patient, the femoral opening-wedge osteotomy with blade-plate fixation, and tibial closing-wedge osteotomy with plate fixation, restored almost normal knee congruency to prevent lateral unicompartmental degenerative deterioration of the knee.

Effect of aluminum on markers of bone formation resorption in chronic hemodialysis patients

Background: T`he prevalence of aluminum (Al)-related toxicity in hemodialysis (HD) patients has declined. However, some HD patients continue to receive Al-based phosphate binders, in part because of the expense of Al-free binders.

Objective: To explore the effect of Al-based binders and their discontinuation on iron status, and markers of bone formation resorption in HD patients.

Methods: Following an initial screen of serum Al levels in 37 HD patients, a second screening was performed after discontinuation of Al-based binders in a 2-year follow-up. A desferrioxamine (DFO; 5 mg/kg) test, and assessment of iron status and bone markers were conducted in the second screening.

Results: Mean serum Al level was initially 27.8 ± 10.3 μg/L. Thirteen patients had a serum Al >30 μg/L, a level considered possibly toxic. There was a positive correlation between serum Al levels, HD duration, and cumulative dose of Al-based binder. At the second screening, the mean serum Al level decreased to 12.5 ± 7.4 μg/L. The mean serum Al level increased to 26.0 ± 14.7 μg/L post-DFO, but in none of the patients did the change in serum Al exceed the 50 μg/L threshold associated with Al-induced bone disease. The decrease in serum Al level was associated with a significant increase in intact parathyroid hormone (iPTH) whereas total alkaline phosphatase did not change.

Conclusions: We recommend that if Al-based phosphate binders are used in HD patients, serum Al level, iron, and markers of bone formation resorption be closely monitored to ensure safe use of these drugs.

Once-weekly teriparatide in hemodialysis patients with hypoparathyroidism and low bone mass: a prospective study

Once-weekly 56.5-μg teriparatide treatment was significantly associated with the increase in lumbar spine bone mineral density at 48 weeks among hemodialysis patients with hypoparathyroidism and low bone mass; however, discontinuation of treatment because of adverse events was frequently observed. Careful monitoring for adverse events should be required.

INTRODUCTION

Once-weekly 56.5-μg teriparatide is reportedly effective for treating osteoporotic patients without renal insufficiency. However, little is known about the efficacy and safety of once-weekly teriparatide in hemodialysis patients.

METHODS

We conducted a 48-week prospective, observational cohort study including 22 hemodialysis patients aged 20 years or older with hypoparathyroidism and low bone mass who received once-weekly teriparatide at 56.5 μg at a tertiary care hospital between January 2013 and January 2015. Primary outcomes were within-subject percent changes of bone mineral density (BMD) at the lumbar spine, femoral neck, and distal one-third radius at 24 and 48 weeks. Secondary outcomes included percent changes of serum bone turnover markers (osteocalcin, bone-specific alkaline phosphatase (BAP), N-terminal propeptide of procollagen type 1 (P1NP), and tartrate-resistant acid phosphatase 5b (TRAP-5b)). Adverse events were evaluated.

RESULTS

The BMD increased at the lumbar spine by 3.3 ± 1.9 % (mean ± SEM) and 3.0 ± 1.8 % at 24 and 48 weeks but not in the femoral neck and distal one-third radius. Serum osteocalcin, BAP, and P1NP increased significantly at 4 weeks, maintaining higher concentrations up to 48 weeks, although TRAP-5b decreased gradually during treatment. The baseline BAP was significantly associated with the 48-week percent change in lumbar spine BMD. Transient hypotension was the most common adverse event. Ten patients discontinued treatment because of adverse events.

CONCLUSIONS

Once-weekly teriparatide was associated with increased lumbar spine BMD in hemodialysis patients with hypoparathyroidism and low bone mass. Careful monitoring should be required for treatment of such patients.

Treatment of adynamic bone disease in a haemodialysis patient with teriparatide

Prevalence of adynamic bone disease (ABD), characterized by low bone turnover and absence or a reduced number of osteoblasts and osteoclasts, is increasing steadily over the last years. We present a dialysis patient, with recurrent bone fractures and biopsy-proven ABD, who was treated with teriparatide. Nine months after initiation of treatment, iPTH plasma levels increased to 520 pg/mL and a second bone biopsy revealed high bone turnover, normal mineralization and normal bone volume. Two years later, iPTH was 250-350 pg/dL and bone metabolism parameters within normal range. The probable utility of teriparatide in the treatment of ABD in dialysis patients is discussed.

(18)F-fluoride positron emission tomography measurements of regional bone formation in hemodialysis patients with suspected adynamic bone disease

(18)F-fluoride positron emission tomography ((18)F-PET) allows the assessment of regional bone formation and could have a role in the diagnosis of adynamic bone disease (ABD) in patients with chronic kidney disease (CKD). The purpose of this study was to examine bone formation at multiple sites of the skeleton in hemodialysis patients (CKD5D) and assess the correlation with bone biopsy. Seven CKD5D patients with suspected ABD and 12 osteoporotic postmenopausal women underwent an (18)F-PET scan, and bone plasma clearance, K i, was measured at ten skeletal regions of interest (ROI). Fifteen subjects had a transiliac bone biopsy following double tetracycline labeling. Two CKD5D patients had ABD confirmed by biopsy. There was significant heterogeneity in K i between skeletal sites, ranging from 0.008 at the forearm to 0.028 mL/min/mL at the spine in the CKD5D group. There were no significant differences in K i between the two study groups or between the two subjects with ABD and the other CKD5D subjects at any skeletal ROI. Five biopsies from the CKD5D patients had single tetracycline labels only, including the two with ABD. Using an imputed value of 0.3 μm/day for mineral apposition rate (MAR) for biopsies with single labels, no significant correlations were observed between lumbar spine K i corrected for BMAD (K i/BMAD) and bone formation rate (BFR/BS), or MAR. When biopsies with single labels were excluded, a significant correlation was observed between K i/BMAD and MAR (r = 0.81, p = 0.008) but not BFR/BS. Further studies are required to establish the sensitivity of (18)F-PET as a diagnostic tool for identifying CKD patients with ABD.

The clinical utility of serum tartrate-resistant acid phosphatase 5b in the assessment of bone resorption in patients on peritoneal dialysis

OBJECTIVES

Serum tartrate-resistant acid phosphatase 5b (TRACP5b) is a bone resorption marker used in the assessment of bone metabolic status. The present study was designed to determine the clinical characteristics and utility of measuring serum TRACP5b levels in peritoneal dialysis (PD) patients.

DESIGN

Cross-sectional study.

PATIENTS

Forty-one patients receiving PD treatment in a single centre.

MEASUREMENT

Serum levels of the bone turnover markers TRACP5b, N-terminal cross-linking telopeptide of type 1 collagen (NTX), bone-specific alkaline phosphatase (BAP), and parathyroid hormone (PTH) were simultaneously measured. The correlation of serum TRACP5b with other established bone markers was analysed after logarithmic transformation. Multivariate linear regression analysis was performed to examine the effects of both renal and peritoneal Kt/V (an index for solute clearance) for urea on bone markers using age, sex, body mass index, and PTH as covariates. Bone markers were also measured in three patients before and after treatment with cinacalcet hydrochloride, alphacalcidol, and raloxifene hydrochloride.

RESULTS

Log TRACP5b was significantly correlated with log NTX, log BAP and log PTH. In the multivariate analysis, peritoneal Kt/V was not correlated with log NTX, log BAP or log TRACP5b. In contrast, renal Kt/V was significantly correlated with log NTX only. Responses to drug treatment were more accurately determined from serum TRACP5b and BAP than from serum NTX.

CONCLUSIONS

Serum TRACP5b and BAP are potentially useful biomarkers for the evaluation of bone turnover in PD patients because they correlate well with other established bone markers and they are not influenced by renal and peritoneal clearances.

Immunosuppressive agents and bone disease in renal transplant patients with hypercalcemia

Renal transplantation is the definitive treatment for many metabolic abnormalities of uremic patients, although it is only partially effective for renal osteodystrophy, which may interact with posttransplant renal osteopathy. Osteopenic-osteoporotic syndrome represents, together with fractures secondary to osteoporosis and osteonecrosis, the bone complication most related to renal transplantation. Several factors contribute to the pathogenesis of posttransplantation osteoporosis, particularly immunosuppressive treatment. In this study, we evaluated the prevalence of factors related to posttransplant renal osteopathy and the clinical impact of immunosuppressive protocols. We studied 24 renal transplant recipients with hypercalcemia. Glomerular filtration rate was >50 mL/min. Mean age, time on dialysis, and time from transplantation were 49.6, 5.4, and 6.9 years, respectively. We evaluated serum and urine calcium and phosphorus, calcitonin, parathormone, bone-specific alkaline phosphatase, osteocalcin, urine deoxypyridinoline, telopeptide of type 1 procollagen, 1,25-(OH)(2) and 25-OH vitamin D, parathyroid ultrasound, and computerized bone mineralometry. The combination of sirolimus and steroids resulted in the most disadvantageous outcomes regarding alkaline phosphatase and mineralometry. Calcineurin inhibitors did not significantly influence bone metabolism markers; mycophenolate mofetil evidenced no effect on bone. According to the literature, steroids account for the abnormalities found in our patients and in severe osteopenia. Several factors may contribute to the development of osteoporosis and fractures in transplantation patients, although they are overcome by the prominent effect of steroids. In patients at high risk of osteoporosis, steroid-free therapy should be considered. Everolimus is indicated for diseases with bone loss. Combined therapy with everolimus and mycophenolic acid without cyclosporine and steroids, seemed to be particularly indicated. Prophylactic treatments should be commenced early. No single marker was useful to diagnose posttransplant renal osteopathy. The definitive diagnosis should be made by bone biopsy during transplantation, and noninvasive procedures, such as densitometry and evaluation of biologic markers, may be useful during follow-up.

Vascular calcifications and renal osteodystrophy in chronic hemodialysis patients: what is the relationship between them?

INTRODUCTION

Vascular calcifications (VCs) and renal osteodystrophy (ROD) are frequently seen together and represent the major causes of morbidity and mortality in hemodialysis (HD) patients. Some studies suggest a pathogenic link between them, but there is no consensus as yet regarding this issue. The main objective of our study was to establish whether there is any relation between VCs and ROD in our HD patients. We evaluated the prevalence of VCs and ROD and the relationship between VCs and some clinical and biochemical characteristics of HD patients.

METHODS

We examined radiological signs of VCs and ROD on hands and pelvis bone radiographs in 81 chronic HD patients, and we calculated a VC score on this basis.

RESULTS

We found a significant relation between radiological signs of ROD and those of VC (P = 0.019). The patients with ROD had a higher mean VC score (P = 0.02). By linear regression, the VC score correlated directly with serum calcium (Ca), phosphorus (P), intact parathyroid hormone (iPTH) and CaxP product and inversely with serum albumin. The logistic regression model revealed that ROD, male gender and treatment with calcium salts were predictive of VCs development. There were no associations between VCs and age, HD vintage, diabetes, dialysate Ca concentration, vitamin D treatment, spKt/V, URR and C-reactive protein (CRP) levels.

CONCLUSION

There seems to be a pathogenetic link between bone and artery diseases in chronic HD patients. Both VCs and ROD have a high prevalence. ROD, male gender and treatment with calcium salts are risk factors for VCs.

Prevalence of radiological findings among cases of severe secondary hyperparathyroidism

CONTEXT AND OBJECTIVE

Patients with end stage renal disease (ESRD) and secondary hyperparathyroidism (HPT2) are prone to develop heterotopic calcifications and severe bone disease. Determination of the sites most commonly affected would decrease costs and patients' exposure to X-ray radiation. The aim here was to determine which skeletal sites produce most radiographic findings, in order to evaluate hemodialysis patients with HPT2, and to describe the most prevalent radiographic findings.

DESIGN AND SETTING

This study was cross-sectional, conducted in one center, the Hospital Universitário Clementino Fraga Filho (HUCFF), in Rio de Janeiro, Brazil.

METHODS

Whole-body radiographs were obtained from 73 chronic hemodialysis patients with indications for parathyroidectomy due to severe HPT2. The regions studied were the skull, hands, wrists, clavicles, thoracic and lumbar column, long bones and pelvis. All the radiographs were analyzed by the same two radiologists, with great experience in bone disease interpretation.

RESULTS

The most common abnormality was subperiosteal bone resorption, mostly at the phalanges and distal clavicles (94% of patients, each). 'Rugger jersey spine' sign was found in 27%. Pathological fractures and deformities were seen in 27% and 33%, respectively. Calcifications were presented in 80%, mostly at the forearm fistula (42%), abdominal aorta and lower limb arteries (35% each). Brown tumors were present in 37% of the patients, mostly on the face and lower limbs (9% each).

CONCLUSION

The greatest prevalence of bone findings were found on radiographs of the hands, wrists, lateral view of the thoracic and lumbar columns and femurs. The most prevalent findings were bone resorption and ectopic calcifications.

Osteomalacia

The finding of low bone mineral density with a T-score of -2.5 or below on dual energy x-ray absorptiometry is usually reported as indicating that the patient has "osteoporosis" according to the World Health Organization classification, and, in postmenopausal women, it is often assumed that this is due to estrogen deficiency. However, up to one third of postmenopausal women have a secondary cause of low density, including osteomalacia. Osteomalacia is defined as a mineralization defect caused by disorders that lead to decreased mineralization of bone. Clues from the history, physical examination, laboratory tests, and radiographs may indicate that the patient suffers from a form of osteomalacia rather than postmenopausal estrogen deficiency alone. Establishing a diagnosis of osteomalacia when present is critical to proper management of the patient.

Biomarker candidates for cardiovascular disease and bone metabolism disorders in chronic kidney disease: a systems biology perspective

Patients with chronic kidney disease (CKD) show a panel of partially de-regulated serum markers indicative for bone metabolism disorders and cardiovascular diseases (CVDs). This review provides an overview of currently reported biomarker candidates at the interface of kidney disease, bone metabolism disorders and CVDs, and gives details on their functional interplay on the level of protein–protein interaction data. We retrieved 13 publications from 1999 to 2006 reporting 31 genes associated with CVDs, and 46 genes associated with bone metabolism disorders in patients with CKD. We identified these genes to be functionally involved in signal transduction processes, cell communication, immunity and defence, as well as skeletal development. On the basis of the given set of 77 genes further 276 interacting proteins were identified using reference data on known protein interactions. Their functional interplay was estimated by linking properties reflected by gene expression data characterizing CKD, gene ontology terms as provided by the gene ontology consortium and transcription factor binding site profiles. Highly connected sub-networks of proteins associated with CKD, CVDs or bone metabolism disorders were detected involving proteins like collagens (COL1A1, COL1A2), fibronectin, transforming growth factor-β₁, or components of fibrinogen (FG-α, FG-β, FG-γ). A systems biology approach provides a methodological framework for linking singular biomarker candidates towards deriving functional dependencies among clinically interlinked diseases.