Assessing bone mineralisation in children with chronic kidney disease: what clinical and research tools are available?

Mineral and bone disorder in chronic kidney disease (CKD-MBD) is a triad of biochemical imbalances of calcium, phosphate, parathyroid hormone and vitamin D, bone abnormalities and soft tissue calcification. Maintaining optimal bone health in children with CKD is important to prevent long-term complications, such as fractures, to optimise growth and possibly also to prevent extra-osseous calcification, especially vascular calcification. In this review, we discuss normal bone mineralisation, the pathophysiology of dysregulated homeostasis leading to mineralisation defects in CKD and its clinical consequences. Bone mineralisation is best assessed on bone histology and histomorphometry, but given the rarity with which this is performed, we present an overview of the tools available to clinicians to assess bone mineral density, including serum biomarkers and imaging such as dual-energy X-ray absorptiometry and peripheral quantitative computed tomography. We discuss key studies that have used these techniques, their advantages and disadvantages in childhood CKD and their relationship to biomarkers and bone histomorphometry. Finally, we present recommendations from relevant guidelines-Kidney Disease Improving Global Outcomes and the International Society of Clinical Densitometry-on the use of imaging, biomarkers and bone biopsy in assessing bone mineral density. Given low-level evidence from most paediatric studies, bone imaging and histology remain largely research tools, and current clinical management is guided by serum calcium, phosphate, PTH, vitamin D and alkaline phosphatase levels only.

A 10-year longitudinal follow-up study of a U.K. paediatric transplant population to assess for skin cancer.

BACKGROUND: Our earlier study, published in 2004,found no skin cancer in a cohort of paediatric organ transplant recipients (POTRs) 5-16 years post-transplantation. We re-evaluated the same cohort 10 years later. OBJECTIVES: To determine the prevalence of premalignant and malignant skin lesions and identify known risk factors associated with melanocytic naevi in a U.K. paediatric transplant population. METHODS: Ninety-eight POTRs from the original 2004 study were invited to participate in this longitudinal follow-up study. History of sun exposure, demographics and transplantation details were collected using face-to-face interviews, questionnaires and case note reviews. Skin examination was performed for regional count of malignant lesions, benign and atypical naevi. RESULTS: Of the 98 patients involved in the initial study, 45 POTRs (eight kidney, 37 liver), with a median follow-up of 19 years (range 15-26 years), agreed to participate. Neither skin cancer nor premalignant lesions were detected in these patients. When compared with the 2004 cohort, 41 patients in our current cohort had increased numbers of benign naevi (P < 0·001) with 11 patients having ≥ 50 benign naevi. Seventy-one per cent of benign naevi in our 2014 cohort occurred on sun-exposed sites (13% head/neck, 35% arms and 23% legs). Patients who regularly used sunscreen had more benign naevi on their arms (P = 0·008). CONCLUSIONS: Although skin cancer was not observed in our cohort, we identified a significant increase in the number of benign naevi, particularly in those reporting frequent sunburn and sunscreen use.

Distributed expertise: qualitative study of a British network of multidisciplinary teams supporting parents of children with chronic kidney disease.

BACKGROUND: Long-term childhood conditions are often managed by hospital-based multidisciplinary teams (MDTs) of professionals with discipline specific expertise of a condition, in partnership with parents. However, little evidence exists on professional-parent interactions in this context. An exploration of professionals' accounts of the way they individually and collectively teach parents to manage their child's clinical care at home is, therefore, important for meeting parents' needs, informing policy and educating novice professionals. Using chronic kidney disease as an exemplar this paper reports on one aspect of a study of interactions between professionals and parents in a network of 12 children's kidney units in Britain. METHODS: We conducted semi-structured, qualitative interviews with a convenience sample of 112 professionals (clinical-psychologists, dietitians, doctors, nurses, pharmacists, play-workers, therapists and social workers), exploring accounts of their parent-educative activity. We analysed data using framework and the concept of distributed expertise. RESULTS: Four themes emerged that related to the way expertise was distributed within and across teams: (i) recognizing each other's' expertise, (ii) sharing expertise within the MDT, (iii) language interpretation, and (iv) acting as brokers. Two different professional identifications were also seen to co-exist within MDTs, with participants using the term 'we' both as the intra-professional 'we' (relating to the professional identity) when describing expertise within a disciplinary group (for example: 'As dietitians we aim to give tailored advice to optimize children's growth'), and the inter-professional 'we' (a 'team-identification'), when discussing expertise within the team (for example: 'We work as a team and make sure we're all happy with every aspect of their training before they go home'). CONCLUSIONS: This study highlights the dual identifications implicit in 'being professional' in this context (to the team and to one's profession) as well as the unique role that each member of a team contributes to children's care. Our methodology and results have the potential to be transferred to teams managing other conditions.

Mutation of BSND causes Bartter syndrome with sensorineural deafness and kidney failure.

Antenatal Bartter syndrome (aBS) comprises a heterogeneous group of autosomal recessive salt-losing nephropathies. Identification of three genes that code for renal transporters and channels as responsible for aBS has resulted in new insights into renal salt handling, diuretic action and blood-pressure regulation. A gene locus of a fourth variant of aBS called BSND, which in contrast to the other forms is associated with sensorineural deafness (SND) and renal failure, has been mapped to chromosome 1p. We report here the identification by positional cloning, in a region not covered by the human genome sequencing projects, of a new gene, BSND, as the cause of BSND. We examined ten families with BSND and detected seven different mutations in BSND that probably result in loss of function. In accordance with the phenotype, BSND is expressed in the thin limb and the thick ascending limb of the loop of Henle in the kidney and in the dark cells of the inner ear. The gene encodes a hitherto unknown protein with two putative transmembrane alpha-helices and thus might function as a regulator for ion-transport proteins involved in aBS, or else as a new transporter or channel itself.

Successful isolated liver transplantation in a child with atypical hemolytic uremic syndrome and a mutation in complement factor H.

A male infant was diagnosed with atypical hemolytic uremic syndrome (aHUS) at the age of 5.5 months. Sequencing of the gene (CFH) encoding complement factor H revealed a heterozygous mutation (c.3644G>A, p.Arg1215Gln). Despite maintenance plasmapheresis he developed recurrent episodes of aHUS and vascular access complications while maintaining stable renal function. At the age of 5 years he received an isolated split liver graft following a previously established protocol using pretransplant plasma exchange (PE) and intratransplant plasma infusion. Graft function, renal function and disease remission are preserved 2 years after transplantation. Preemptive liver transplantation prior to the development of end stage renal disease is a valuable option in the management of aHUS associated with CFH mutations.

A randomized trial to assess the impact of early steroid withdrawal on growth in pediatric renal transplantation: the TWIST study.

Minimizing steroid exposure in pediatric renal transplant recipients can improve linear growth and reduce metabolic disorders. This randomized multicenter study investigated the impact of early steroid withdrawal on mean change in height standard deviation score (SDS) and the safety and efficacy of two immunosuppressive regimens during the first 6 months after transplantation. Children received tacrolimus, MMF, two doses of daclizumab and steroids until day 4 (TAC/MMF/DAC, n=98) or tacrolimus, MMF and standard-dose steroids (TAC/MMF/STR, n=98). Mean change in height SDS was 0.16 +/- 0.32 with TAC/MMF/DAC and 0.03 +/- 0.32 with TAC/MMF/STR. The mean treatment group difference was 0.13 (p < 0.005 [95% CI 0.04-0.22]), 0.21 in prepubertal (p = 0.009 [95% CI 0.05-0.36]) and 0.05 in pubertal children (p = ns). Frequency of biopsy-proven acute rejection was 10.2%, TAC/MMF/DAC, and 7.1%, TAC/MMF/STR. Patient and graft survival and renal function were similar. Significantly greater reductions in total cholesterol and triglycerides but significantly higher incidences of infection and anemia were found with TAC/MMF/DAC (p < 0.05 all comparisons). Early steroid withdrawal significantly aided growth at 6 months more so in prepubertal than pubertal children. This was accompanied by significantly better lipid and glucose metabolism profiles without increases in graft rejection or loss.

Human hypertension caused by mutations in WNK kinases.

Hypertension is a major public health problem of largely unknown cause. Here, we identify two genes causing pseudohypoaldosteronism type II, a Mendelian trait featuring hypertension, increased renal salt reabsorption, and impaired K+ and H+ excretion. Both genes encode members of the WNK family of serine-threonine kinases. Disease-causing mutations in WNK1 are large intronic deletions that increase WNK1 expression. The mutations in WNK4 are missense, which cluster in a short, highly conserved segment of the encoded protein. Both proteins localize to the distal nephron, a kidney segment involved in salt, K+, and pH homeostasis. WNK1 is cytoplasmic, whereas WNK4 localizes to tight junctions. The WNK kinases and their associated signaling pathway(s) may offer new targets for the development of antihypertensive drugs.

Nodular glomerulosclerosis in a patient with cystic fibrosis, but not diabetes mellitus: A paediatric case.

BACKGROUND: Nodular glomerulosclerosis is seen in insulin dependent diabetic patients with nephropathy. Kimmelstiel-Wilson nodules on biopsy are considered pathognomonic. Diabetic nephropathy is a spectrum of glomerular and tubular disease which correlates with the duration of the diabetes and the extent of glycaemic control. CASE REPORT: An eleven year old girl with cystic fibrosis was referred with persistent heavy proteinuria. She underwent a renal biopsy which revealed nodular glomerulosclerosis with Kimmelstiel-Wilson-like nodules. Her investigations for diabetes were negative and she was treated with enalapril. CONCLUSION: Nodular glomerulosclerosis in the absence of diabetes and poor glycaemic control have not previously been reported in a paediatric patient. In adult patients without diabetes, smoking, hypertension, hypercholestrolaemia and extrarenal vascular disease have been implicated. The proteinuria decreased after commencement of treatment with enalapril. A recurrence of proteinuria responded to a dose increase.

Glomerular vascular cell adhesion molecule-1 expression in renal vasculitis.

AIMS: To study the expression of cell adhesion molecules in the renal biopsy specimens of patients with systemic vasculitis and Henoch-Schönlein purpura (HSP); to correlate this with the severity of glomerular inflammation. METHODS: Renal biopsy specimens obtained from eight patients with untreated systemic vasculitis (four with Wegener's granulomatosis and four with microscopic polyarteritis), eight with HSP and nine controls (four with normal histopathology and five with thin glomerular basement membrane disease) were stained using the alkaline phosphatase anti-alkaline phosphatase method with monoclonal antibodies directed against intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and E-selectin. RESULTS: Biopsy specimens of normal kidneys expressed ICAM-1 in glomerular endocapillary cells, Bowman's capsule epithelium, interstitial cells and interstitial vascular endothelium, and VCAM-1 in Bowman's capsule epithelium, proximal tubular epithelium and interstitial vascular endothelium. No staining with antibody directed against E-selectin was seen in any of the biopsy specimens. Biopsy specimens of patients with a vasculitic glomerulonephritis (segmental necrotising glomerulonephritis) expressed VCAM-1 in glomerular endocapillary cells (four of eight patients with systemic vasculitis; two of eight patients with HSP). In patients with a systemic vasculitis glomerular VCAM-1 expression was associated with a more severe renal lesoin (44, 50, 60, and 65% of glomeruli involved) than in those not showing glomerular VCAM-1 expression (3, 3, 11, and 39% of glomeruli involved). CONCLUSION: Expression of VCAM-1 by glomerular endocapillary cells in renal biopsy specimens raises the possibility that recruitment of VLA-4 bearing leucocytes may contribute to glomerular injury in Wegener's granulomatosis and microscopic polyarteritis.

Plasminogen activator inhibitor activity in diarrhoea-associated haemolytic uraemic syndrome.

In the haemolytic uraemic syndrome (HUS), platelet microthrombi and deposition of fibrin in glomeruli may contribute to the development of renal failure. The balance of procoagulant and fibrinolytic activities in the renal vasculature may therefore have an important role. We measured plasminogen-activator inhibitor (PAI) activity in the plasma of 81 children with diarrhoea-associated (D+) HUS, and found elevated PAI activity in many patients. When we categorized patients by need for dialysis, only the dialysed group had significantly higher levels of activity, compared with a group of normal controls. We also compared PAI activity with patient outcome after one year, and found that those with a poor outcome had significantly higher PAI activity than those with a good outcome. We suggest that plasma PAI activity may be an acute marker for dialysis requirement in HUS, and may have prognostic value for long-term outcome. The possible role of PAI in the pathogenesis of HUS requires further investigation.

Hypertension: a cause of growth impairment.

The effects of high blood pressure on growth are not fully understood and while hypertension may be associated with failure to thrive, hypertension causing failure to thrive in children is poorly documented. We describe four children presenting with failure to thrive due to hypertension consequent to various aetiologies. Control of hypertension with appropriate therapy resulted in improved growth. The exact pathogenesis of failure to thrive in hypertensive children is not known. These cases demonstrate the importance of careful measurement of blood pressure in children with failure to thrive.

Comparison of ribosome-inactivating proteins in the induction of apoptosis.

The aim of this study was to evaluate the ability of verocytotoxin-1 (VT1), VT1 B chain alone, ricin and a hybrid toxin (RASTA2) consisting of ricin A chain linked to VT1 B chain to inhibit protein synthesis and to induce apoptosis. The lethal effects of the toxins were compared using vero cells (originating from green African monkey kidney tissue). As previously described cell death occurred through apoptosis which was quantified using the diphenylamine assay. DNA fragmentation was seen with VT1 at 10 pg/ml but there was no effect with B chain alone. Fragmentation with ricin was seen at 10 ng/ml and with RASTA2 at 1 ng/ml. Protein synthesis inhibition was measured by [(35)S]methionine incorporation. VT1 had an IC50 of 0.0024 ng/ml, B chain alone was ineffective at inhibiting protein synthesis. Ricin had an IC50 of 0.39 ng/ml and RASTA2 of 1.7 ng/ml. In vero cells the B chain of these toxins does not participate in cell killing.

A comparison of the effects of verocytotoxin-1 on primary human renal cell cultures.

Infection with verocytotoxin-producing Escherichia coli causes haemolytic uraemic syndrome (HUS). Verocytotoxin-1 (VT1) is cytopathic to renal microvascular endothelial cells in culture, supporting the hypothesis that the vasculopathy of HUS is caused directly by the toxic action of VT1 on cells. We provide evidence that VT1 inhibits protein synthesis in primary cultures of glomerular epithelial cells (GE), cortical tubular epithelial cells (CTE) and mesangial cells (MC). Using 100 pg/ml of VT1 we saw a decrease in protein synthesis to 14.3+/-1.9% in vero cells (a primate cell line), 1.7+/-0.3% in GE, 0.9+/-0.4% in CTE and 74.8+/-1.3% in MC at 24 h. The human renal epithelial cells are at least as sensitive as vero cells to the protein synthesis inhibitory effects of VT1 if not more so. Cell viability decreased in all cultures as measured by MTT reduction, neutral red incorporation and lactate dehydrogenase release and followed the same pattern of susceptibility as for protein synthesis inhibition. However, unlike vero cells, death occurred without DNA fragmentation. Cell sensitivity was greatest in cells which bound more VT1.

Care in the use of ibuprofen as an antipyretic in children.

Ibuprofen is being widely used as an antipyretic in children. Recent studies indicate that it is as efficacious and with no significant difference in side-effects when compared to paracetamol. We describe three cases that illustrate that renal complications can occur when ibuprofen is prescribed in the presence of intravascular volume depletion and/or pre-existing renal problems. We discuss the mode of action of ibuprofen and recommend that its use as an antiypretic in children should be avoided in actual or potential intravascular volume contraction and in cases with pre-existing renal problems.

Early risk factors in pediatric renal transplantation at a single center.

BACKGROUND/PURPOSE: Renal transplantation is the preferred treatment for renal failure in childhood, but the incidence of graft failure is generally higher than that in adult recipients. A single center was studied to determine if there were any correctable factors that could contribute to graft failure. METHODS: Recipient, donor, and perioperative factors were analyzed using standard statistical tests in 59 pediatric renal transplants performed between 1992 and 1995 using standard cyclosporin-based immunosuppression. RESULTS: Three factors were found to be significantly different between those recipients with good graft function and those who either died or were returned to dialysis. Any history of donor hypotension was a detrimental factor (P < .05, chi(2) test). In addition, those with failed grafts were more likely to have received their grafts from younger donors (P = .025, Mann Whitney U test). A third risk factor was a low postoperative central venous pressure in those whose graft ultimately failed (P = .0012, Mann Whitney U test). CONCLUSIONS: With a pediatric recipient who is stable and has a low priority for a renal graft, small donors, particularly those who have experienced hypotension, should be considered not suitable for transplantation. The chances of a successful graft can be improved by good communication between surgeon, pediatrician, and anesthetist. The importance of maintaining a positive central venous pressure is emphasised.

Dental abnormalities in Schimke immuno-osseous dysplasia.

Described for the first time in 1971, Schimke immuno-osseous dysplasia (SIOD) is an autosomal-recessive multisystem disorder that is caused by bi-allelic mutations of SMARCAL1, which encodes a DNA annealing helicase. To define better the dental anomalies of SIOD, we reviewed the records from SIOD patients with identified bi-allelic SMARCAL1 mutations, and we found that 66.0% had microdontia, hypodontia, or malformed deciduous and permanent molars. Immunohistochemical analyses showed expression of SMARCAL1 in all developing teeth, raising the possibility that the malformations are cell-autonomous consequences of SMARCAL1 deficiency. We also found that stimulation of cultured skin fibroblasts from SIOD patients with the tooth morphogens WNT3A, BMP4, and TGFß1 identified altered transcriptional responses, raising the hypothesis that the dental malformations arise in part from altered responses to developmental morphogens. To the best of our knowledge, this is the first systematic study of the dental anomalies associated with SIOD.

Skin surveillance of a U.K. paediatric transplant population.

BACKGROUND: Solid organ transplant recipients are at increased risk of skin cancer. Melanoma is less common than nonmelanoma skin cancer (NMSC) although the relative proportion of melanoma among skin cancers has been shown to be higher in paediatric than adult recipients. Multiple melanocytic naevi and/or atypical naevi may be a risk factor for the development of melanoma. The relationship between naevus counts and phenotypic characteristics, disease-related variables and sun exposure has not been explored in paediatric transplant patients. OBJECTIVES: To determine the prevalence of premalignant and malignant skin lesions and to identify known risk factors associated with benign and atypical melanocytic naevi in a U.K. paediatric transplant population. METHODS: Paediatric (< or = 19 years) renal and liver transplant patients, who were 5 or more years post-transplantation, were reviewed over 12 months. Lifetime history of sun exposure, episodes of sunburn, sunny holidays, sunscreen use, sun bed use, demographic and transplantation details were collected using interview, questionnaire and case note review. A skin examination was performed for regional counts of malignant lesions, benign and atypical naevi. RESULTS: Ninety-eight patients (82 liver, 13 renal, three multiorgan) with a median follow up of 9 years (range 5-16) were reviewed. Neither skin cancer nor premalignant lesions for NMSC were detected in this group. Eighty-five patients had benign naevi (median 6, range 1-57). Clinical risk factors for increased counts of benign naevi included increasing age (P = 0.03), more episodes of sunburn (P = 0.003) and prolonged treatment with cyclosporin (P = 0.009). The presence of atypical naevi in six patients was significantly associated with more episodes of sunburn (P = 0.006) and more transplants (P = 0.04). Other variables including phenotype, skin type, sun exposure, holidays abroad, residence abroad and total duration of immunosuppression did not correlate with benign or atypical naevus counts. CONCLUSIONS: Skin cancer was not observed in paediatric solid organ transplant recipients who were 5-16 years post-transplantation. Both benign and atypical naevus counts were higher in children with frequent episodes of sunburn. As both naevi and sunburn are risk factors for melanoma, we should target fair-skinned transplant recipients with naevi for intensive sun avoidance education. A prospective, longitudinal follow-up study should determine the onset of skin cancer post-transplantation and the significance of benign and atypical naevus counts in this cohort.