Retrospective analysis of the clinical characteristics of adefovir dipivoxil-induced Fanconi's syndrome in the Chinese population.

WHAT IS KNOWN AND OBJECTIVE: To explore the clinical characteristics of adefovir dipivoxil-induced Fanconi's syndrome in the Chinese population and provide a reference for rational drug use in the clinic. METHODS: By searching the CNKI, Wanfang, Chinese VIP, PubMed/MEDLINE, Web of Knowledge, Ovid, Elsevier and SpringerLink databases during 1 January 2008 to 31 December 2019, 78 studies of ADV-induced Fanconi's syndrome involving a total of 110 patients were collected and analysed retrospectively. RESULTS AND DISCUSSION: Prolonged usage of adefovir dipivoxil at low doses to treat hepatitis B might cause Fanconi's syndrome as the first symptom, especially for use over 12 months.The main clinical manifestation was bone pain accompanied by hypophosphataemia, elevated alkaline phosphatase (ALP), urine glycosuria and urine protein. X-rays and bone mineral density (BMD) examinations were mainly used to characterized osteoporosis. The patients had pain relief within 1 week to 1 month, and the biochemical indicators returned to normal within from 2 to 4 months. WHAT IS NEW AND CONCLUSION: Sufficient attention is required before and during exposure to long-term ADV therapy. The clinical picture, laboratory and radiograph alterations are important clues for ADV-induced Fanconi's syndrome.

A case of entecavir-induced Fanconi syndrome.

Acquired Fanconi syndrome has been associated with the long-term ingestion of several nucleoside analogs used to treat chronic hepatitis B virus infection. However, the nucleoside analog entecavir has not been found to cause nephrotoxicity. We report a case of entecavir-induced Fanconi syndrome. Our patient was a 73-year-old man admitted to our hospital because of renal dysfunction. He also presented with hyperaminoaciduria, renal diabetes, phosphaturia, hypophosphatemia, hypokalemia, hypouricemia, and hyperchloremic metabolic acidosis, supporting a diagnosis of Fanconi syndrome. In this case, the cause of Fanconi syndrome was most likely entecavir, which had been administered as needed depending on his renal function for 5 years. After drug discontinuation and replacement with tenofovir alafenamide fumarate therapy once a week, the patient's kidney function recovered and electrolyte anomalies partially improved. We highlight the fact that entecavir may induce severe renal dysfunction, which can cause the development of Fanconi syndrome; therefore, close monitoring of proximal tubular function is recommended during entecavir therapy.

Glucosuria without diabetes: key to the diagnosis of fragility fractures due to Fanconi syndrome.

A 64-year-old woman had fragility fractures which caused her to have gross deformities and confined her to bed. These were initially ascribed to vitamin D deficiency. However, despite correction of the deficiency, she did not improve. A review of previous records already showed glucosuria in the absence of diabetes, but this finding was overlooked. Eight years into the disease, it was realised that the glucosuria despite normal blood sugar could also mean that the patient was losing other substances needed for proper bone formation. Further investigations showed hypophosphataemia, renal phosphate wasting, hypokalaemia, mild metabolic acidosis, alkaline urine pH, hypouricaemia and aminoaciduria, all compatible with a proximal renal tubular defect (Fanconi syndrome). The fragility fractures were due to poor bone mineralisation because of hypophosphataemia induced by the inability of the kidneys to conserve phosphorus.

Urinary Clara Cell Protein in Kidney Transplant Patients: A Preliminary Study.

OBJECTIVE: The aim of this exploratory study was to analyze the urinary excretion of Clara cell protein (CC16), a new marker of proximal tubular dysfunction (PTD), in kidney transplantation (KT). MATERIALS AND METHODS: Urinary concentrations of CC16, ß2-microglobulin (ß2m), and N-acetyl-glucosaminidase (NAG) were measured in 50 KT patients (72% men; mean age 50.4 ± 12.4 years; diabetes in 24%; duration of KT 4.3 ± 3.1 years) and 10 healthy controls (6 men; mean age 33.6 ± 13.4 years). RESULTS: Urinary levels of ß2m, NAG, and CC16 were significantly higher in KT patients than in controls: ß2m: 0.77 (interquartile range [IQ] 0.22 to 4.62) g/g vs 0.069 (IQ 0.05 to 0.10) g/g; NAG: 3.16 (IQ 2.09 to 5.33) U/g vs 1.73 (IQ 1.25 to 2.07) U/g; CC16: 26.01 (IQ 8.62 to 123.3) g/g vs 2.51 (IQ 0.83 to 7.18) g/g (P < .001). Elevated levels of ß2m, NAG, and CC16 were found in 81%, 28%, and 71% of KT patients, respectively. Urinary levels of ß2m, NAG, and CC16 significantly increase as glomerular filtration rate (GFR) decreases. Interestingly, in patients with GFR >60 mL/min, we still found high levels of ß2m, NAG, and CC16 in 77%, 13%, and 52%, respectively. Diabetic subjects had significant higher levels of the 3 markers compared with nondiabetic subjects, without differences in albumin excretion or GFR. CC16 showed a positive correlation with urinary albumin (r = 0.42, P < .001), NAG (r = 0.352, P < .05), and ß2m (r = 0.75, P < .001). CONCLUSION: PTD is highly prevalent in KT patients. This is the first study that analyzes CC16 in KT patients, showing that the urinary excretion of this protein is significantly increased in this population. Further studies are needed to examine the clinical value of CC16 in KT patients.

Intragraft transcriptional profiling of renal transplant patients with tubular dysfunction reveals mechanisms underlying graft injury and recovery.

BACKGROUND: Proximal tubular dysfunction (PTD) is associated with a decreased long-term graft survival in renal transplant patients and can be detected by the elevation of urinary tubular proteins. This study investigated transcriptional changes in biopsies from renal transplant patients with PTD to disclose molecular mechanisms underlying graft injury and functional recovery. METHODS: Thirty-three renal transplant patients with high urinary levels of retinol-binding protein, a biomarker of PTD, were enrolled in the study. The initial immunosuppressive scheme included azathioprine, cyclosporine, and steroids. After randomization, 18 patients (group 2) had their treatment modified by reducing cyclosporine dosage and substituting azathioprine for mycophenolate mofetil, while the other 15 patients (group 1) remained under the initial scheme. Patients were biopsied at enrollment and after 12 months of follow-up, and paired comparisons were performed between their intragraft gene expression profiles. The differential transcriptome profiles were analyzed by constructing gene co-expression networks and identifying enriched functions and central nodes in each network. RESULTS: Only the alternative immunosuppressive scheme used in group 2 ameliorated renal function and tubular proteinuria after 12 months of follow-up. Intragraft molecular changes observed in group 2 were linked to autophagy, extracellular matrix, and adaptive immunity. Conversely, gene expression changes in group 1 were related to fibrosis, endocytosis, ubiquitination, and endoplasmic reticulum stress. CONCLUSION: These results suggest that molecular networks associated with the control of endocytosis, autophagy, protein overload, fibrosis, and adaptive immunity may be involved in improvement of graft function.

A Rare Case of Acquired Fanconi's Syndrome With Monoclonal Gammopathy in an Infant.

BACKGROUND: Monoclonal gammopathies associated with acquired Fanconi's syndrome (AFS) have been reported in the adult population. AFS is characterized by renal dysfunction resulting in proteinuria, aminoaciduria, hypophosphatemia, glucosuria, and hyperchloremic metabolic acidosis. In this case report, we document the clinical and laboratory findings of a preterm infant with features of both AFS and monoclonal gammopathy in the urine. METHODS: Clinical suspicion of AFS prompted the following laboratory studies to be performed: urine protein electrophoresis (UPEP), urine immunofixation, and urine amino acid analysis with high performance liquid chromatography (HPLC). RESULTS: Urine amino acid analysis revealed aminoaciduria. On UPEP, nonselective glomerular proteinuria was seen with a faint band in the gamma region. Urine immunofixation confirmed the presence of a monoclonal IgG lambda component with free monoclonal lambda light chains. CONCLUSION: To the best of our knowledge, this is the first case of pediatric AFS reported with a monoclonal gammopathy and monoclonal free light chains.

Two patients with HNF4A-related congenital hyperinsulinism and renal tubular dysfunction: A clinical variation which includes transient hepatic dysfunction.

The HNF4A p.R76W mutation causes congenital hyperinsulinism with Fanconi syndrome. Here, we report two cases who also presented with increased urinary calcium excretion and one had a transient hepatic dysfunction with hepatomegaly. Clinical variations including transient liver dysfunction is a likely mutation-specific clinical characteristic.

Ailing bones and failing kidneys: a case of chronic cadmium toxicity.

Heavy metal toxicity is often caused by occupational exposure. Chronic cadmium toxicity is a significant health concern among workers engaged in zinc smelting, battery production and silver jewellery industries, particularly in developing countries. We report the case of a 48-year-old man who presented with severe osteoporosis, impaired renal function and acquired Fanconi syndrome. He was finally diagnosed with chronic cadmium toxicity resulting from long-term occupational exposure. Cadmium has a long biological half-life and there is no effective treatment for people who are exposed to it. Therefore, an early diagnosis and prevention of further exposure are important.

The use of biomarkers for assessing HAART-associated renal toxicity in HIV-infected patients.

Renal toxicity has become an important issue in HIV-infected patients receiving highly active antiretroviral therapy (HAART). Several biomarkers are available for monitoring renal function, although no consensus exists on how best to apply these tools in HIV infection. The best biomarker is the glomerular filtration rate (GFR), and several creatinine-based estimates equations of GFR are widely used in HIV infection, with clinical advantages for the equation developed by Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI). Although serum cystatin C has been proposed as a more sensitive marker of renal dysfunction in HIV infection, it may be affected by ongoing inflammation. Tubular dysfunction can be simple or complex, depending on whether the tubular transport of one or more substances is affected. Multiple renal tubular dysfunction or Fanconi syndrome is characterized by alterations in the reabsorption of glucose, amino acids, phosphate and often also bicarbonate. Therefore, Fanconi syndrome would be the tip of the iceberg, and the most unusual and severe manifestation. In the last years, several low molecular weight proteins as markers of tubular alteration, including retinol-binding protein, b2-microglobulin, and neutrophil gelatinase associated lipocalin have become available. Different studies have shown differences in urine concentrations of these proteins in patients receiving tenofovir, but again, no consistent data have shown their clinical usefulness in predicting the clinical consequences of tubular alteration. Thus, we review findings from recent studies performed in this area to describe the performance of new biomarkers for renal damage in HIV-infected patients.

Analysis of molecular forms of urine Retinol-Binding Protein in Fanconi Syndrome and design of an accurate immunoassay.

BACKGROUND: Retinol-Binding Protein in urine (uRBP), a biomarker for the proximal renal tubular disease of congenital and acquired Fanconi Syndrome (FS) occurs in multiple forms. However these have not had quantitative mass spectrometric (MS) analysis, nor is there a validated assay for defined molecular species of uRBP with linearity on sample dilution. METHODS: A 'Top-down' MS approach identified distinct forms of uRBP differing by only one amino acid. Based on this, we designed a dual-monoclonal antibody-based fluorescence immunoassay calibrated with intact plasma RBP4. RESULTS: LC-MS showed that uRBP in FS (one Dent disease urine) comprised intact plasma RBP4 and C-terminal-truncated RBP4, desL-RBP4 and desLL-RBP4 in molar ratio 2:2:1. DELFIA® assay calibrated with plasma RBP4, formulated with two monoclonal antibodies (HyTest, Finland), mAb48 for capture and biotinylated-mAb42 for detection, provided good sensitivity (1 µg/L), working range>500 µg/L and good linearity on sample dilution. The three predominant forms of uRBP were equipotent over the assay working range. uRBP reference range was <3 µg/mmol creatinine and FS patients had concentrations of 1000-5000 µg/mmol creatinine. CONCLUSIONS: Using 'Top-down' MS analysis of uRBP we devised an accurate, linear, fluorescence immunoassay with defined RBP molecular targets optimal for uRBP measurement. Discrimination of elevated uRBP from the upper limit of normal was some 10-fold greater than previous assays.

A case of acquired Fanconi syndrome induced by zoledronic acid.

A 61-year-old woman with metastatic breast cancer was diagnosed as having acquired Fanconi syndrome. In this case, the cause of this syndrome was most likely zoledronic acid (Zometa), which had been infused intravenously at a dose of 4 mg over 15 minutes weekly because of malignancy-associated hypercalcemia. Zoledronic acid is nephrotoxic and may induce severe tubular dysfunction, which can cause development of Fanconi syndrome. Therefore, close monitoring of proximal tubular function is recommended during therapy with zoledronic acid, especially when frequent administration of zoledronic acid is needed.

Novel techniques and newer markers for the evaluation of "proximal tubular dysfunction".

Renal Fanconi syndromes are both clinically challenging and physiologically fascinating. The diagnosis requires a certain index of suspicion to correctly identify the clinical symptomatology and pursue the appropriate laboratory evaluations. The renal Fanconi syndrome (FS) is a defect of proximal tubular function attributable to different rare inherited diseases or acquired disorders caused by a multitude of exogenous agents. It can manifest as complete or incomplete FS, characterized by low molecular weight proteinuria, glucosuria, aminoaciduria, and loss of electrolytes, bicarbonate and lactate. Implementation of new methods and recent findings from urinary proteome pattern in patients with renal FS has led to the identification of new markers for proximal tubular dysfunction. Future combined proteomic and metabonomic studies will provide additional potential biomarkers and may help to gain novel insights in the diagnosis and differentiation of the various forms of FS. Moreover, the observation of poor renal uptake of 99 mTc-DMSA in patients with tubular proteinuria, which is not fully understood yet, may also help to elucidate the individual basis of FS in early stages. This review focuses on the new advances in the evaluation of proximal tubular dysfunction in various forms of Fanconi syndrome.

Urine proteomic analysis: use of two-dimensional gel electrophoresis, isotope coded affinity tags, and capillary electrophoresis.

The identities and abundance levels of proteins excreted in urine are not only key indicators of diseases associated with renal function but are also indicators of the overall health of individuals. Urine specimens are readily available and provide a noninvasive means to assess and diagnose many disease states. Proteins in urine originate from two sources: the ultrafiltrate of plasma, and those that are shed from the urinary tract. The protein concentration in urine excreted from a normal adult is approximately 150 mg/day, and is typically not greater than 10 mg/100 mL in any single specimen. Following precipitation, concentration, and fractionation methods, proteins of interest from urine samples can be separated, identified, and quantified. One of the most commonly used techniques in the field of urine proteomics is gel electrophoresis followed by identification with mass spectrometry and protein database search algorithms. In this chapter, two-dimensional gel electrophoresis (2-DE) will be discussed, along with less frequently applied techniques, such as isotope coded affinity tags (ICAT) and capillary electrophoresis (CE). Publications discussing the application of these techniques to urine proteomic analyses of healthy individuals and urinary disease biomarker discovery will also be summarized.

Advances in urinary proteome analysis and biomarker discovery in pediatric renal disease.

Recent progress in proteomic analysis and strategies for the identification of clinically useful biomarkers in biofluids has led to the identification of urine as an excellent non-invasive reservoir for biomarkers of disease. Urinary biomarkers have been identified and validated on independent cohorts in different high-incidence adult renal diseases, including diabetic nephropathy, chronic kidney disease and immunoglobulin A-nephropathy, but also in extrarenal disease, such as coronary artery disease. Unfortunately, this type of research is underrepresented in the pediatric population. Here, we present the rare studies in the pediatric population that identified potential clinically useful urinary biomarkers in ureteropelvic junction (UPJ) obstruction and renal Fanconi syndrome. These studies, although limited in number, clearly show the potential of urinary proteomics, especially in the pediatric population. It is anticipated that the advances made in the adult population, the lessons learned on the use of appropriate statistics and the inclusion of independent blinded validation cohorts in these types of studies will rapidly lead to clinical useful urinary biomarkers for other pediatric (renal) disease in a population where non-invasive analysis is particularly appreciated.

Urinary proteome pattern in children with renal Fanconi syndrome.

BACKGROUND: The renal Fanconi syndrome (FS) is characterized by renal glucosuria, loss of electrolytes, bicarbonate and lactate, generalized hyperaminoaciduria and low-molecular-weight proteinuria. We studied the urinary low-molecular-weight proteome to identify excreted peptides indicative of a pathogenetic mechanism leading to tubular dysfunction. METHODS: We established a urinary proteome pattern using capillary electrophoresis mass spectrometry (CE-MS) of 7 paediatric patients with cystinosis and 6 patients with ifosfamide-induced FS as the study group, and 54 healthy volunteers and 45 patients suffering from other renal diseases such as lupus nephritis (n = 8), focal segmental glomerulosclerosis (n = 27), minimal change disease (n = 7) and membranous glomerulonephritis (n = 3) as controls. Consequently, we conducted a blinded study consisting of 11 FS patients and 9 patients with renal disease other than FS. Additionally, we applied this pattern to 294 previously measured samples of patients with different renal diseases. Amino acid sequences of some marker proteins were obtained. RESULTS: Specificity for detecting FS was 89% and sensitivity was 82%. The marker peptides constituting the proteome pattern are fragments derived from osteopontin, uromodulin and collagen alpha-1. CONCLUSIONS: CE-MS can be used to diagnose FS in paediatric patients and might be a future tool for the non-invasive diagnosis of FS. The reduced amount of the marker proteins osteopontin and uromodulin indicates loss of function of tubular excretion in all patients suffering from FS regardless of the underlying cause. In addition, the six different fragments of the collagen alpha-1 (I) chain were either elevated or reduced in the urine. This indicates a change of proteases in collagen degradation as observed in interstitial fibrosis. These changes were prominent irrespectively of the stages of FS. This indicates fibrosis as an early starting pathogenetic reason for the development of renal insufficiency in FS patients.

A pivotal role of the human kidney in catabolism of HDL protein components apolipoprotein A-I and A-IV but not of A-II.

Renal handling of major HDL components was studied by analyzing urine from patients with Fanconi syndrome, a rare renal proximal tubular reabsorption failure, including dysfunction of the kidney HDL receptor, cubilin. A high urinary excretion of apolipoprotein A-I and A-IV corresponding to a major part of the metabolism of these proteins was measured. In contrast, no urinary excretion of apolipoprotein A-II which is more hydrophobic and tighter bound to HDL was found. Control urines displayed absence of the three apolipoproteins. Urinary excretion of phospholipids, triglycerides, cholesterol and cholesterol esters in patients was as low as in controls. In conclusion, these data indicate that the human kidney is a major site for filtered nascent apolipoprotein A-I and A-IV but not for HDL particles.

A systematic review of the accuracy and utility of early markers of Ifosfamide-induced proximal tubulopathy in survivors of childhood cancers.

This study was conducted to identify and assess the accuracy and utility of any early markers of clinically significant proximal tubulopathy in children treated with ifosfamide chemotherapy. Ifosfamide is widely used either as a solitary agent or in conjunction with various other chemotherapeutic agents in treating solid tumors of childhood. It is highly effective but can cause short-term and long-term damage to kidneys, most commonly resulting in a tubular nephropathy and/or glomerular dysfunction. This may lead to chronic renal failure and metabolic bone disease in long-term survivors of childhood cancer. Multiple electronic databases (Cochrane, MEDLINE, EMBASE) were searched for primary studies describing the predictive value of early blood or urine tests to predict proximal tubulopathy. Citation searching (using reference lists and Science Citation Index searches) was also undertaken. Analysis was undertaken using criteria suggested by the MOOSE (Meta-analysis of Observational Studies in Epidemiology) collaboration. Studies were reviewed by at least 2 authors and disagreements resolved by consensus. Initial searches revealed approximately 310 studies of which 38 papers were selected for full analysis. Only 4 papers described the predictive value of early markers proximal tubular nephropathy. The remaining studies estimated prevalence of acute or chronic nephropathy without presenting predictive data. Of the 4 papers selected for analysis, 2 papers assessed the value of beta-2 microglobulinuria, and 3 addressed quantitative aminoaciduria. Test characteristics ranged from sensitivities of 82 to 100% and specificities of 84 to 100%, although the confidence intervals around these estimates were wide. Given the paucity of data, to consider further the use of early markers of proximal tubular nephropathy a prospective evaluation of patients who have been treated with ifosfamide based regimes should be undertaken.