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.

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.

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.

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.

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.

A prospective, randomized, multicenter trial of tacrolimus-based therapy with or without basiliximab in pediatric renal transplantation.

In a 6-month, multicenter, randomized, controlled, open-label, parallel-group trial, we investigated the efficacy and safety of adding basiliximab to a standard tacrolimus-based regimen in pediatric renal transplant recipients. Patients < 18 years received tacrolimus/azathioprine/steroids (TAS, n = 93) or tacrolimus/azathioprine/steroids/basiliximab (TAS + B, n = 99). Target tacrolimus levels were 10-20 ng/mL between days 0-21 and 5-15 ng/mL thereafter. Steroid dosing was identical in both groups. Basiliximab was administered at 10 mg (patients < 40 kg) or 20 mg (patients > or = 40 kg) within 4 h of reperfusion; the same dose was repeated on day 4. Biopsy-proven acute rejection rates were 20.4% (TAS) and 19.2% (TAS + B); steroid-resistant acute rejection rates were 3.2% and 3.0%, respectively. Patient survival was 100%; graft survival rates were 95% in both arms. The nature and incidence of adverse events were similar in both arms except toxic nephropathy and abdominal pain, which were significantly higher in the TAS + B arm (14.1% vs. 4.3%; p = 0.03 and 11.1% vs. 2.2%; p = 0.02; respectively). Median serum creatinine concentrations at 6 months were 86 micromol/L in the TAS and 91 micromol/L in the TAS + B arm; glomerular filtration rate was 79.4 and 77.6 (mL/min/1.73 m2), respectively. Adding basiliximab to a tacrolimus-based regimen is safe in pediatric patients, but does not improve clinical efficacy.

Renal function following liver transplantation for unresectable hepatoblastoma.

Combination of cyclosporine (CsA) and tacrolimus immunosuppression post-liver transplantation (LT) and the chemotherapeutic drugs used to treat hepatoblastoma (HB), are nephrotoxic. We aimed to determine the severity and duration of nephrotoxicity in children following LT for unresectable HB. We reviewed all children undergoing LT for unresectable HB at the Liver Unit, Birmingham Children's Hospital, UK, from 1991 to July 2000. Thirty-six children undergoing LT for biliary atresia, matched for age and sex, were selected as controls to compare pre- and post-LT renal function. Renal function was determined by estimation of glomerular filtration rate (eGFR) derived from plasma creatinine using Schwartz's formula. Twelve children with HB (mean age of diagnosis 33 months) who underwent LT (mean age 47 months) and 36 controls (mean age of LT 34 months) were studied. CsA was the main immunosuppressive drug used in each group. The median eGFR before, and at 3, 6, 12, 24 and 36 months after LT in HB group was significantly lower than controls (93 vs. 152, 66 vs. 79, 62 vs. 86, 66 vs. 87, 64 vs. 94, 53 vs. 90 mL/min/1.73 m2, respectively; 0.01 < p < 0.03). The reductions in the median eGFR of both the HB group and controls before and at 36 months after LT were 49 and 41%, respectively. At 36 months after LT, there was a trend for partial recovery of the eGFR in the controls but not in the HB group. Children who underwent LT for unresectable HB had renal dysfunction before transplantation that persisted for 36 months after LT.

ARC syndrome: an expanding range of phenotypes.

AIM: To describe the clinical phenotype in infants with ARC syndrome, the association of arthrogryposis, renal tubular acidosis, and cholestasis. METHODS: The medical records for six patients with ARC syndrome were reviewed, presenting over 10 years to three paediatric referral centres. RESULTS: All patients had the typical pattern of arthrogryposis. Renal Fanconi syndrome was present in all but one patient, who presented with nephrogenic diabetes insipidus. Although all patients had severe cholestasis, serum gamma glutamyltransferase values were normal. Many of our patients showed dysmorphic features or ichthyosis. All had recurrent febrile illnesses, diarrhoea, and failed to thrive. Blood films revealed abnormally large platelets. CONCLUSIONS: ARC syndrome exhibits notable clinical variability and may not be as rare as previously thought. The association of Fanconi syndrome, ichthyosis, dysmorphism, jaundice, and diarrhoea has previously been reported as a separate syndrome: our observations indicate that it is part of the ARC spectrum.

Cerebellar defect associated with Schimke immuno-osseous dysplasia.

UNLABELLED: We report the finding of an absent cerebellar hemisphere and partial absence of the cerebellar vermis in a child with dysmorphic features, spondyloepiphyseal dysplasia, steroid resistant nephrotic syndrome secondary to focal segmental glomerulosclerosis and T-cell lymphopenia (Schimke immuno-osseous dysplasia). These findings have not, to our knowledge, been described before and are likely to represent the consequence of a vascular event either in-utero or in early infancy. CONCLUSION: Cerebral imaging should be performed early in the course of the disease and should be repeated if further neurological events develop.

Microscopic polyarteritis with renal and cerebral involvement.

We report a 15-year-old girl who presented with renal failure requiring dialysis and a diagnosis of p-ANCA-associated vasculitis. She subsequently developed cerebral vasculitis during treatment with oral cyclophosphamide and prednisolone. Treatment with intravenous cyclophosphamide and plasma exchange produced a complete recovery.

Manifestations and treatment of Schimke immuno-osseous dysplasia: 14 new cases and a review of the literature.

UNLABELLED: Schimke immuno-osseous dysplasia (SIOD) is a rare autosomal recessive spondylo-epiphyseal dysplasia. The characteristic features of SIOD include 1) short stature with hyperpigmented macules and an unusual facies, 2) proteinuria with progressive renal failure, 3) lymphopenia with recurrent infections, and 4) cerebral ischaemia. Although 25 patients have been reported with this disorder, the clinical course and phenotype of SIOD are not well characterized. This report summarizes the clinical findings, course and treatment of reported patients and includes 14 additional patients with SIOD. We emphasize the high incidence of cerebral ischaemia and ocular abnormalities, define the high incidence of thyroid dysfunction and blood cytopenia, and confirm the absence of effective and durable medical therapies. CONCLUSION: Schimke immuno-osseous dysplasia is a multi-system autosomal recessive disorder with variable expression that affects the skeletal, renal, immune, vascular, and haematopoietic systems. Medical therapy is limited especially for more severely affected individuals.

A laboratory model of toxin-induced hemolytic uremic syndrome.

BACKGROUND: Verocytotoxin-producing (Shiga-like toxin-producing) Escherichia coli infection is the principal cause of hemolytic uremic syndrome (HUS). The pathogenesis is unclear, and there is a need for animal models. These are impeded by the different distribution of verocytotoxin receptors between species. We have circumvented this restriction using ricin, which gains entry into cells via various galactose receptors. Like verocytotoxin, ricin specifically cleaves a single adenine from ribosomal RNA. METHODS: Rats were given ricin at a dose of 6.7 micrograms/100 g body wt, with or without lipopolysaccharide at 10 micrograms/100 g body wt. Lipopolysaccharide alone or saline were used as controls. Changes in glomerular filtration rate, hematological parameters, histology, and plasma cytokine concentrations were measured. RESULTS: Extensive glomerular thrombosis, pyknotic nuclei, and an infiltration of ED1-positive cells into glomeruli were observed eight hours after an injection of ricin. Other vascular beds were unaffected. Histologic changes were preceded by oliguric renal failure, hemolysis, and thrombocytopenia. Ricin produced a rise in plasma concentrations of monocyte chemotactic protein-1, > tumor necrosis factor-alpha, > interleukin-1 beta, > interleukin-6. Interferon-gamma showed a small increase at the end of the experiment. CONCLUSIONS: Ricin induces glomerular thrombotic microangiopathy, closely resembling that which occurs in verocytotoxin-producing E. coli-induced HUS. As in HUS, high concentrations of proinflammatory cytokines are present, which are probably a result of cytokine superinduction by the toxin.

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.

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.

Renal biopsy diagnosis in children presenting with haematuria.

We reviewed the clinical and renal biopsy findings in 322 children presenting during the years 1975-1996 with recurrent macro- or continuous microscopic haematuria persisting for > or =6 months, in whom non-glomerular causes were excluded. Family involvement was documented for first-degree relatives. All biopsies were examined by light microscopy, 317 by electron microscopy and 315 by immunofluorescence. Biopsies were classified as IgA nephropathy (78), Alport nephropathy (86), thin basement membrane nephropathy (TMN) (50), miscellaneous glomerulonephritis (32), hilar vasculopathy (28) and normal glomeruli (48). Although microscopic haematuria alone was more frequent in Alport nephropathy and TMN, the pattern of haematuria in individual patients did not predict histology. Of patients with familial haematuria, 79% of biopsies showed either Alport nephropathy or TMN. Hilar vasculopathy was observed both in isolation and in all abnormal histological categories.

The late histologic findings in diarrhea-associated hemolytic uremic syndrome.

Kidney biopsies were undertaken for persisting proteinuria 3.3 to 7 years (mean 5.4 years) from the onset of diarrhea-associated hemolytic uremic syndrome (D + HUS) in 5 boys and 2 girls (age at presentation mean 3.2 years, range 1.0 to 9.7 years). At 1 year the mean early morning urine protein/creatinine ratio was 100 mg/mmol, and the mean glomerular filtration rate was 65 mL/min/1.73 m2. At 5 years the mean early morning urine protein/creatinine ratio was 81 mg/mmol, and the mean glomerular filtration rate was 73 mL/min/1.73 m2. The biopsy specimens were compared with those of 7 age- and sex-matched children who were investigated for isolated persistent microscopic hematuria but in whom no abnormality was detected. Global glomerulosclerosis was noted in 6 patients with D + HUS, and 2 of these had segmental sclerosing lesions. Tubular atrophy and interstitial scarring were seen in all but 1 patients. The glomeruli in the D + HUS group were significantly larger than in the control group (P < .01). These findings are typically found in kidneys with reduced nephron numbers and are compatible with changes of hyperperfusion and hyperfiltration in surviving nephrons. Long-term follow-up of patients with D + HUS and proteinuria is advisable.

Variable presentation of primary hyperoxaluria type 1 in 2 patients homozygous for a novel combined deletion and insertion mutation in exon 8 of the AGXT gene.

Two unrelated patients of Pakistani origin presented with primary hyperoxaluria type 1 (PH1) at 4 months and 3 years of age, respectively. While the younger patient failed to thrive and suffered from early renal failure, the older one showed a relatively benign history with urolithiasis as the main feature of the disease. In both patients the diagnosis was confirmed by assessment of alanine:glyoxylate aminotransferase catalytic and immunoreactivity in liver biopsy specimens. The underlying genetic defect was found to be a combined deletion and insertion in exon 8 which alters the reading frame of the protein. The nucleotide change introduces a Stu1 restriction site which facilitated typing of additional family members. Both patients and a further affected brother were homozygous for this mutation, while their parents were heterozygous for it. This mutation is the first deletion/insertion identified in PH1. Although rare in our PH1 patient cohort (2.5% of alleles), the finding of 2 homozygous apparently unrelated individuals of the same ethnic origin suggests that it may prove worthwhile to screen other Asian patients for this mutation. These PH1 cases present further evidence that factors other than genotype contribute significantly to the clinical presentation and severity of PH1.

Cytokines in haemolytic uraemic syndrome associated with verocytotoxin-producing Escherichia coli infection.

The proinflammatory cytokines tumour necrosis factor-alpha (TNF-alpha) interleukin (IL)-1 beta, IL-6, and IL-8 were measured in plasma and urine samples from 19 children with verocytotoxin-producing Escherichia coli (VTEC) induced haemolytic uraemic syndrome (HUS) and 30 controls. TNF-alpha was detected in the plasma of two cases and one control; IL-6 in the plasma of one, and the urine of two cases, and in the plasma of one control. IL-1 beta and IL-8 were each identified in eight of the 19 cases and in one and two controls respectively. Urinary IL-8 was found in seven cases, four of whom had plasma concentrations below the limit of detection suggesting renal secretion of this cytokine. Cytokine concentrations did not correlate with peripheral blood neutrophil count at onset of disease. These data confirm the systemic release of cytokines responsible for the coordination of acute inflammatory processes in some children with VTEC induced HUS.