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Background: Fanconi-Bickel syndrome (FBS) is a rare autosomal recessive disorder characterized by impaired glucose and galactose utilization as well as proximal renal tubular dysfunction., Methods: Clinical, biochemical, genetic, treatment, and follow-up data for 11 pediatric patients with FBS were retrospectively analysed., Results: Hepatomegaly (10/11), short stature (10/11) and hypophosphataemic rickets (7/11) were the most common initial symptoms. At diagnosis, all patients had decreased fasting blood glucose (FBG), plasma bicarbonate (HCO 3 - ) and serum phosphorus, as well as elevated liver transaminases, alkaline phosphatase (AKP) and proximal renal tubular dysfunction. Two infant patients were misdiagnosed with transient neonatal diabetes mellitus. After therapy with uncooked cornstarch and conventional rickets treatment, remission of hepatomegaly was observed in all patients, with significant improvements in pre-prandial blood glucose, liver transaminases, triglyceride, plasma HCO 3 - and AKP (p < 0.05). At the last follow-up, 5/7 patients with elevated AKP had nephrocalcinosis. The mean height standard deviation score (Ht SDS) of eight patients with regular treatment increased from - 4.1 to -3.5 (p = 0.02). Recombinant human growth hormone (rhGH) was administered to 4/9 patients, but their Ht SDS did not improve significantly (p = 0.13). Fourteen variants of the SLC2A2 gene were identified, with six being novel, among which one was recurrent: c.1217T > G (p.L406R) (allele frequency: 4/22, 18%). Patients with biallelic missense variants showed milder metabolic acidosis than those with null variants. Two of five patients from nonconsanguineous families with rare homozygous variations showed 5.3 Mb and 36.6 Mb of homozygosity surrounding the variants, respectively; a region of homozygosity (ROH) involving the entire chromosome 3 covering the SLC2A2 gene, suggesting uniparental disomy 3, was detected in one patient., Conclusions: Early diagnosis of FBS is difficult due to the heterogeneity of initial symptoms. Although short stature is a major issue of treatment for FBS, rhGH is not recommended in FBS patients who have normal GH stimulation tests. Patients with biallelic null variants may require alkali supplementation since urine bicarbonate loss is genetically related. ROH is a mechanism for rare homozygous variants of FBS in nonconsanguineous families., (© 2024. The Author(s).)

We report on an 80-year-old man diagnosed with Fanconi syndrome induced by mizoribine after 4 weeks of administration to treat membranous nephropathy. Mizoribine is an oral immunosuppressant that inhibits inosine monophosphate dehydrogenase and is widely used in Japan for the treatment of autoimmune diseases and nephrotic syndrome, as well as after renal transplantation. Acquired Fanconi syndrome is often caused by drugs (antibacterial, antiviral, anticancer, and anticonvulsant drugs) and is sometimes caused by autoimmune diseases, monoclonal light chain-associated diseases, or heavy metal poisoning. In our patient, hypokalemia, hypophosphatemia, glucosuria, hypouricemia, and severe proteinuria resolved gradually after discontinuation of mizoribine administration, despite oral administration of prednisolone followed by a single intravenous injection of rituximab. The patient was ultimately diagnosed with Fanconi syndrome induced by mizoribine based on his clinical course and his typical laboratory data with the absence of proximal tubular acidosis. To our knowledge, this is the first report of Fanconi syndrome possibly induced by mizoribine. Although the precise mechanism by which mizoribine induces proximal tubular dysfunction is unknown, we suggest that nephrologists should be aware of the onset of Fanconi syndrome, a rare complication during mizoribine treatment., (© 2022. The Author(s) under exclusive licence to The Japan Society of Nephrology.)

Infantile nephropathic cystinosis (INC) is an inheritable lysosomal storage disorder characterized by lysosomal cystine accumulation, progressive kidney disease, and multiple extrarenal complications (ERCs). Cysteamine postpones the onset of end-stage kidney disease (ESKD) and reduces the incidence of ERCs; however, cysteamine is generally initiated upon establishment of the renal Fanconi syndrome (FS) and partial loss of kidney function, whereas data on long-term effects of cysteamine administered from neonatal age are lacking. An international multicenter retrospective cohort study of siblings with INC was set up to investigate the outcome in relation to age at initiation of cysteamine versus CTNS genotype, with attention to patients treated with cysteamine from neonatal age. None of the siblings treated from neonatal age (n = 9; age 10 ± 6 years) had reached ESKD, while 22% of their index counterparts (n = 9; age 14 ± 5 years) had commenced renal replacement therapy. Siblings treated with cysteamine from the onset of symptoms at a younger age compared with their index counterparts, reached ESKD at a significant older age (13 ± 3 vs. 10 ± 3 years, p = 0.002). In contrast, no significant difference in ERCs was observed between sibling and index patients, independently from the age at initiation of cysteamine. The CTNS genotype had no impact on the overall outcome in this cohort. In INC, presymptomatic treatment with cysteamine results in a better renal outcome in comparison to treatment initiated from the onset of symptoms. This justifies including cystinosis into newborn screening programs. SYNOPSIS: In infantile nephropathic cystinosis, presymptomatic treatment with cysteamine improves the renal outcome which justifies the inclusion of cystinosis into newborn screening programs., (© 2022 SSIEM.)

Introduction: Nephropathic cystinosis (NC) is a rare, autosomal recessive disorder leading to lysosomal accumulation of cystine. It is caused by mutations in the CTNS gene encoding a cystine cotransporter cystinosin. The infantile (INC) and juvenile (JNC) forms are distinguished. The former, responsible for 95% of cases, is characterized by development of renal Fanconi syndrome, end-stage kidney disease (ESKD), and extrarenal complications. A therapy with cysteamine significantly improves outcomes. There are limited data on NC in the Central Eastern European countries., Objectives: We aimed to evaluate the prevalence, genetic background, and clinical course of NC in the Polish population., Patients and Methods: We performed a retrospective analysis of data of all identified NC patients in Poland., Results: Between 1982 and 2017, 15 patients with NC (13 ICN, 2 JCN) were identified. The most common mutations of the CTNS gene were c.18&#95;c.21delGACT and c.681+1G>A, whereas only 2 patients carried the 57 kb deletion. The majority (11/13) of INC patients with limited access to the cysteamine therapy developed ESKD at a median age of 11 years and 9 of them received kidney transplants. Three INC patients died at a median age of 24 years. In contrast, 2 INC patients treated adequately present normal kidney function and growth at the age of 13 and 11 years. Two JNC patients presented a milder course., Conclusions: The prevalence of NC in Poland is much lower than in the Western countries and its molecular background appears to be different. The unfavorable course in the majority of INC patients was caused by a limited access to the cysteamine treatment.

Nephropathic cystinosis is a rare lysosomal storage disease whose basic defect, impaired transport of cystine out of lysosomes, results in intracellular cystine storage. Affected individuals exhibit renal Fanconi Syndrome in infancy, end-stage kidney disease at approximately 10 years of age, and many other systemic complications. Oral cysteamine therapy mitigates the detrimental effects on glomerular function and prevents most of the late complications of the disease but has not shown benefit with respect to the early tubular damage of cystinosis. This is because cystinosis is generally diagnosed in the second year of life, after the damage to kidney tubular function has already occurred. We longitudinally evaluated 6 infants diagnosed and treated with cysteamine from before 2 months of age. The 4 infants with good compliance with cysteamine and consistently low leucocyte cystine levels maintained normal eGFR values, exhibited only minor degrees of renal Fanconi Syndrome, and maintained normal serum levels of potassium, bicarbonate, phosphate, and calcium without electrolyte or mineral supplementation through 2, 4, 10 and 16 years of age. Thus, renal Fanconi syndrome can be attenuated by early administration of cysteamine and renew the call for molecular-based newborn screening for cystinosis., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Infantile nephropathic cystinosis, due to impaired transport of cystine out of lysosomes, occurs with an incidence of 1 in 100-200,000 live births. It is characterized by renal Fanconi syndrome in the first year of life and glomerular dysfunction progression to end-stage kidney disease by approximately 10 years of age. Treatment with oral cysteamine therapy helps preserve glomerular function, but affected individuals eventually require kidney replacement therapy. This is because glomerular damage had already occurred by the time a child is diagnosed with cystinosis, typically in the second year of life. We performed a retrospective multicenter study to investigate the impact of initiating cysteamine treatment within the first 2 months of life in some infants and comparing two different levels of adherence in patients diagnosed at the typical age. We collected 3983 data points from 55 patients born between 1997 and 2020; 52 patients with 1592 data points could be further evaluated. These data were first analyzed by dividing the patient cohort into three groups: (i) standard treatment start with good adherence, (ii) standard treatment start with less good adherence, and (iii) early treatment start. At every age, mean estimated glomerular filtration rate (eGFR) was higher in early-treated patients than in later-treated patients. Second, a generalized additive mixed model (GAMM) was applied showing that patients with initiation of treatment before 2 months of age are expected to have a 34 ml/min/1.73 m 2 higher eGFR than patients with later treatment start while controlling for adherence and patients' age. These data strongly suggest that oral cysteamine treatment initiated within 2 months of birth preserves kidney function in infantile nephropathic cystinosis and provide evidence of the utility of newborn screening for this disease., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Tenofovir disoproxil is efficacious in the preventing HIV infection as part of a pre-exposure prophylaxis (PrEP) regimen. Although its use has been associated with impaired renal function, instances of Fanconi syndrome are extremely rare. This may change with increased uptake of PrEP., Methods: A 55-year-old male patient (he/him/his) was commenced on PrEP with a baseline estimated glomerular filtration rate (eGFR) of approximately 60mL/min/1.73m2 ., Results: Within 6months, he developed new and worsening proteinuria, glycosuria and aminoaciduria despite no apparent change in eGFR. PrEP was discontinued and his urinary abnormalities rapidly resolved. The patient remains off PrEP., Conclusions: Fanconi syndrome is a rare, but known complication of tenofovir disoproxil. This is the first report related to PrEP in Australia. While tenofovir associated nephrotoxicity in patients taking PrEP is uncommon, the patient's age and pre-existing renal impairment placed him at substantially higher risk. At-risk patients need more frequent monitoring of their eGFR and proteinuria. Urinary protein to creatinine ratio is the preferred to dipstick testing for proteinuria and the latter does not readily detect the low molecular wight proteinuria characteristic of tenofovir toxicity. Early recognition of these patients is essential, as prompt cessation of PrEP can often reverse renal abnormalities.

Background: Fanconi syndrome (FS) can be of primary or secondary origin. Some cases of FS secondary to the use of sodium valproate (VPA) have been described, mostly in children with severe psychomotor retardation who are fed by feeding device. The objetive of this study was to describe patients treated for this entity in our center, comparing them against the published literature., Methods: Descriptive study of our patients and those found in the literature. Epidemiologic and clinical data were collected., Results: We describe seven patients (three to 17 years old) with severe psychomotor retardation and undergoing treatment with VPA. Four presented pathologic fractures before the diagnosis of FS, and in three patients the diagnosis was reached due to abnormal laboratory findings. A review of the published cases was carried out and, including our sample, a total of 42 patients were studied: 51.3% were male, and the median age at diagnosis of FS was 6 years. Severe psychomotor retardation was found in 92.8% of patients, 78% carried a feeding device, and 77.5% received treatment with several antiepileptic drugs. The mean duration of VPA treatment was 5.7 years (range 2 to 7.5 years). Fifteen patients (37.5%) had bone complications. The resolution time of FS after discontinuation of drug therapy ranged from two to 19 months (median 4 months)., Conclusions: FS related to VPA is a rare complication, but it should be considered in patients with epilepsy, especially if they have severe psychomotor retardation, are users of feeding devices, and receive other antiepileptic treatments in addition to VPA., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Children with infantile nephropathic cystinosis (INC), an inherited lysosomal storage disease resulting in cystine accumulation in all body cells, are prone to progressive chronic kidney disease (CKD), impaired growth and reduced weight gain; however, systematic anthropometric analyses are lacking. In this prospective multicenter study we investigated linear growth, body proportion, body mass index (BMI), upper arm fat area (UFA) and biochemical parameters in 43 pediatric INC patients with CKD stages 1 to 5 and 49 age-matched CKD controls, with 193 annual measurements. INC patients showed more impaired height than CKD controls (-1.8 vs -0.7 z-score; P < .001), despite adequate cysteamine therapy, treatment for Fanconi syndrome and more frequent use of growth hormone. Only the youngest INC patients shared the same body pattern with CKD controls characterized by preferential impairment of leg length and rather preserved trunk length. In late-prepuberty, body pattern changed only in INC patients due to improved leg growth and more impaired trunk length. Mean UFA z-score in INC patients was slightly reduced in early childhood and progressively decreased thereafter reaching -0.8 z-score in adolescence, while CKD controls showed a steady increase in standardized BMI and UFA especially during adolescent age. Menarche in female INC patients was significantly delayed compared to CKD controls. Our data indicate that with age and progression of disease, pediatric INC patients undergo unique changes of body growth and fat stores that are distinct from those with CKD stemming from other causes, suggesting other factors apart from CKD to contribute to this development. Pediatric patients with infantile nephropathic cystinosis display more severe impaired linear growth than other peer CKD patients, despite of cysteamine treatment, supplementation for Fanconi syndrome, and more frequent use of growth hormone, with a distinct change of body proportions and overall lower body fat., (© 2022 The Authors. Journal of Inherited Metabolic Disease published by John Wiley & Sons Ltd on behalf of SSIEM.)

Fanconi-Bickel syndrome (FBS) is a rare autosomal recessive disease, resulting from mutations in the SLC2A2 gene, causing impaired glucose transporter 2 protein transporter protein function, impaired glucose and galactose utilisation, hepatorenal glycogen accumulation and organ dysfunction. Clinical features include failure to thrive, hepatomegaly, rickets, short stature and delayed puberty. Therapy includes electrolyte supplementation and uncooked cornstarch. We present a 15-year-old boy diagnosed with FBS in infancy. Growth velocity was normal on standard treatment until age 8.5 years, at which time growth failure led to a diagnosis of acquired growth hormone (GH) deficiency. Initiation of recombinant human GH (rhGH) replacement of 0.25 μg/kg/week resulted in marked improvement in growth velocity and height. While short stature is expected in FBS, growth velocity that falls below the normal range despite adequate therapy should prompt further evaluation. Our case suggests that acquired GH deficiency can arise in FBS and benefits from rhGH therapy., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2021. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Nephropathic cystinosis is a rare and severe metabolic disease leading to an accumulation of cystine in lysosomes which especially harms kidney function. A lifelong therapy with the aminothiol cysteamine can delay the development of end-stage renal disease and the necessity of kidney transplantation. The purpose of our study was to compare the effectiveness of immediate-release and delayed-release cysteamine on cystine and cysteamine levels as well as assessing the onset of adverse effects., Methods: We retrospectively analysed cystine and cysteamine levels of 17 patients after a single dose of immediate-release cysteamine (Cystagon®, Mylan Pharmaceuticals, Canonsburg, PA and Recordati Pharma GmbH) as well as a single dose of delayed-release cysteamine (Procysbi®; Horizon Pharma USA and Chiesi Farmaceutici S.p.A., Parma, Italy) respectively. Data were collected during a period of three years in the context of optimizing the individual treatment regimens. The dose of DR-cysteamine was reduced to 70% of the equivalent dose of IR-cysteamine. The efficacy of both formulas in depleting white blood cells' cystine levels and their side effects were compared., Results: Immediate (IR)- and delayed-release (DR) cysteamine effectively decreased intracellular cystine levels under the target value of 0.5 nmol cystine/mg protein, while fewer side effects occurred under DR-cysteamine. Mean maximum levels of cysteamine were reached after 60 min with IR-cysteamine and after 180 min with DR-cysteamine., Conclusion: A therapy with DR-cysteamine is as effective as IR-cysteamine while less side effects were reported. Our data show that DR-cysteamine should be dosed higher than 70% of the equivalent dose of IR-cysteamine in order to decrease cystine levels over an extended period of time. Moreover, our data suggest increasing the dosing scheme of Procysbi® to three times daily, to prevent a rapid decrease and achieve a steadier decline in cystine levels. Due to the more convenient dosing scheme, DR-cysteamine might ameliorate therapy adherence and improve patients' quality of life., (© 2021. The Author(s).)

Background: Leptospirosis is an underdiagnosed bacterial infection with nonspecific symptoms, hence, a diagnostic challenge. Identifying a case of leptospirosis in Switzerland is uncommon. Although kidney complications are frequent in severe forms, including tubular dysfunction, observing this complication is rare in our country. We report the case of a patient with leptospirosis and kidney dysfunction, which was notable for proximal tubulopathy. This case report describes the diagnosis and management of this patient's tubular dysfunction., Case Presentation: A 34-year-old Caucasian male known for alcohol and drug abuse presented to our emergency department suffering from severe pain in the lower limbs, jaundice, and fever with flu-like symptoms. Physical examination was not contributory. Blood tests showed cytopenia, elevated inflammatory markers, acute kidney injury, and altered liver function tests with predominant cholestasis. Urinalysis showed proteinuria and significant glycosuria without concomitant hyperglycemia. Leptospirosis was suspected and confirmed by both positive serum polymerase chain reaction and elevated immunoglobulin M for Leptospira interrogans. The patient was treated with intravenous amoxicillin-clavulanate and doxycycline for 7 days. After antibiotic treatment, symptoms disappeared, and kidney dysfunction completely resolved., Conclusion: Our case focuses on the description of leptospirosis-related acute kidney injury with proximal tubular dysfunction, which is a rare finding in Switzerland., (© 2021. The Author(s).)

Glucose is an essential energy source for cells. In humans, its passive diffusion through the cell membrane is facilitated by members of the glucose transporter family (GLUT, SLC2 gene family). GLUT2 transports both glucose and fructose with low affinity and plays a critical role in glucose sensing mechanisms. Alterations in the function or expression of GLUT2 are involved in the Fanconi-Bickel syndrome, diabetes, and cancer. Distinguishing GLUT2 transport in tissues where other GLUTs coexist is challenging due to the low affinity of GLUT2 for glucose and fructose and the scarcity of GLUT-specific modulators. By combining in silico ligand screening of an inward-facing conformation model of GLUT2 and glucose uptake assays in a hexose transporter-deficient yeast strain, in which the GLUT1-5 can be expressed individually, we identified eleven new GLUT2 inhibitors (IC 50 ranging from 0.61 to 19.3 µM). Among them, nine were GLUT2-selective, one inhibited GLUT1-4 (pan-Class I GLUT inhibitor), and another inhibited GLUT5 only. All these inhibitors dock to the substrate cavity periphery, close to the large cytosolic loop connecting the two transporter halves, outside the substrate-binding site. The GLUT2 inhibitors described here have various applications; GLUT2-specific inhibitors can serve as tools to examine the pathophysiological role of GLUT2 relative to other GLUTs, the pan-Class I GLUT inhibitor can block glucose entry in cancer cells, and the GLUT2/GLUT5 inhibitor can reduce the intestinal absorption of fructose to combat the harmful effects of a high-fructose diet.

Tenofovir disoproxil fumarate (TDF) is an antiretroviral drug widely used as a first-line treatment of hepatitis B virus (HBV) and HIV. Increasing evidence has emerged associating its use with the development of Fanconi syndrome, renal insufficiency and bone disease. We report a case of a 61-year-old woman with a remote history of liver transplant for cirrhosis due to HBV. Over 1 year, the patient had recurrent falls, generalised myalgias and arthralgias, misdiagnosed as fibromyalgia. We discuss a complication of her transplant treatment regimen with the drug TDF leading to a rare but reversible disorder: tenofovir-induced Fanconi osteomalacia with renal phosphate wasting. Though recognised, this rare disorder was initially likely missed due to clinical unfamiliarity with the diagnosis, concomitant psychiatric symptoms and premature diagnostic closure., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2021. No commercial re-use. See rights and permissions. Published by BMJ.)

Fanconi syndrome (FS) is a severe grade of drug-induced proximal tubule toxicity. There are numerous causes for acquired FS, and drug toxicity is one of the most common. FS is known to be associated with the nucleoside reverse transcriptase inhibitor (NRTI) tenofovir disoproxil fumarate (TDF). TDF is often used in combination with emtricitabine (FTC) for preexposure prophylaxis (PrEP) of human immunodeficiency virus (HIV) infection. TDF/FTC-induced FS has been observed as a dose-related phenomenon that is directly correlated to kidney function, high levels of absorption of the drug into the proximal tubule, and interactions with other medications. This case report describes a patient who acquired FS after starting TDF/FTC for PrEP in the setting of chronic kidney disease (CKD) with concomitant tacrolimus therapy, a known nephrotoxic agent.

More than 150 cases of Fanconi syndrome (FS) or hypophosphatemia osteomalacia induced by low-dose adefovir dipivoxil (ADV) have been reported since 2002, when ADV was introduced for the long-term treatment of hepatitis B virus (HBV) infection. Because the life expectancy of HBV-infected individuals has increased, the adverse effects of long-term treatment with antiviral therapies are increasingly observed, and nephrotoxicity is one of the most severe adverse effects of ADV. Therefore, the number of cases may be far higher than reported. Moreover, ADV-induced FS is often misdiagnosed or diagnosed long after it first develops. ADV-induced FS may seriously decrease patient quality of life and lead to bone fractures and even disability. Although progress has been made in the identification of biomarkers and treatments, few systematic clinical guidelines or clinical reviews for FS induced by ADV have been reported. In this study, we highlighted the recent progress toward understanding of FS induced by ADV, described a clinical case, and summarized the primary characteristics and laboratory findings of this disease.

The kidney proximal tubule function relies on oxidative phosphorylation (OXPHOS), thus mitochondrial dysfunction is characteristic of acute kidney injury (AKI). Maleic acid (MA) can induce an experimental model of Fanconi syndrome that is associated to oxidative stress and decreased oxygen consumption. Sulforaphane (SF) is an antioxidant known to protect against MA-induced AKI. The molecular basis by which SF maintains the bioenergetics in MA-induced AKI is not fully understood. To achieve it, rats were submitted to a protective scheme: SF (1 mg/kg/day i.p.) for four days and, at the fourth day, they received a single dose of MA (400 mg/kg i.p.), getting four main experimental groups: (1) control (CT), (2) MA-nephropathy (MA), (3) SF-protected and (4) SF-control (SF). Additionally, a similar protective schema was tested in cultured NRK-52E cells with different concentrations of SF and MA. In the animal model, SF prevented the MA-induced alterations: decrease in fatty acid-related oxygen consumption rate, OXPHOS capacity, mitochondrial membrane potential (Ψ mt ), and the activity of complex I (CI) as its monomeric and supercomplexes forms; the antioxidant also increased the activity of cytochrome c oxidase as well as mitochondrial biogenesis markers. Thus, SF prevented the MA-induced increase in fission, mitophagy and autophagy markers. In NRK-52E cells, we found that SF prevented the MA-induced cell death, increased mitochondrial mass and ameliorated the loss of Ψ mt . We concluded that SF-induced biogenesis protects against mitochondrial dysfunction maintaining Ψ mt , activities of mitochondrial complexes and supercomplexes, and prevents the extensive fission and mitophagy., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2020 Elsevier Inc. All rights reserved.)

We herein report a 50-year-old woman who suffered from tubulointerstitial nephritis with antimitochondrial M2 antibody, distal renal tubular acidosis, and Fanconi syndrome. Our case also had interstitial pneumonia. After initially successful glucocorticoid therapy, tubulointerstitial nephritis and interstitial pneumonia relapsed. After the second successful round of glucocorticoid therapy, tubulointerstitial nephritis relapsed again and responded to glucocorticoid and azathioprine. This case might indicate (1) the association between pulmonary involvement and tubulointerstitial nephritis with antimitochondrial antibodies and (2) the need for a maintenance dose of glucocorticoid and immunosuppressants in tubulointerstitial nephritis with antimitochondrial antibodies.

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.

Cystinosis is an autosomal recessive storage disease due to impaired transport of cystine out of lysosomes. Since the accumulation of intracellular cystine affects all organs and tissues, the management of cystinosis requires a specialized multidisciplinary team consisting of pediatricians, nephrologists, nutritionists, ophthalmologists, endocrinologists, neurologists' geneticists, and orthopedic surgeons. Treatment with cysteamine can delay or prevent most clinical manifestations of cystinosis, except the renal Fanconi syndrome. Virtually all individuals with classical, nephropathic cystinosis suffer from cystinosis metabolic bone disease (CMBD), related to the renal Fanconi syndrome in infancy and progressive chronic kidney disease (CKD) later in life. Manifestations of CMBD include hypophosphatemic rickets in infancy, and renal osteodystrophy associated with CKD resulting in bone deformities, osteomalacia, osteoporosis, fractures, and short stature. Assessment of CMBD involves monitoring growth, leg deformities, blood levels of phosphate, electrolytes, bicarbonate, calcium, and alkaline phosphatase, periodically obtaining bone radiographs, determining levels of critical hormones and vitamins, such as thyroid hormone, parathyroid hormone, 25(OH) vitamin D, and testosterone in males, and surveillance for nonrenal complications of cystinosis such as myopathy. Treatment includes replacement of urinary losses, cystine depletion with oral cysteamine, vitamin D, hormone replacement, physical therapy, and corrective orthopedic surgery. The recommendations in this article came from an expert meeting on CMBD that took place in Salzburg, Austria, in December 2016., (© 2019 The Authors. Journal of Inherited Metabolic Disease published by John Wiley & Sons Ltd on behalf of SSIEM.)

Light chain-associated Fanconi syndrome (LCFS) is a disorder of renal proximal tubule due to immunoglobulin light chains. Cases of LCFS are rare and mostly sporadically reported, and treatment of this entity is still controversial. This single-center retrospective study included 22 patients diagnosed with LCFS in Peking Union Medical College Hospital. Monoclonal gammopathy of undetermined significance was diagnosed in 13 patients, and overt multiple myeloma in six patients, with two smoldering myeloma and one Waldenstrom macroglobulinemia. Light chain was mostly kappa type (90.9%). Baseline median estimated glomerular filtration rate was 66 (13-126) ml/min/1.73 m 2 , with one patient presented as end-stage renal disease. After a median follow-up of 37 months, three patients died. Twelve patients were treated with chemotherapy, including 7 with bortezomib-based regimens. Renal function was significantly improved in the group of patients who received chemotherapy (p = 0.026). Compared with other chemotherapy regimens, patients with bortezomib-based treatment had a better hematological response (p = 0.027) as well as a better proximal tubule outcome (p = 0.015). Chemotherapy likely outweighs supportive treatment in patients with LCFS. Bortezomib-based regimen seems to be a safe first-line therapy for management of those patients.

Background: Adefovir dipivoxil is a nucleotide analogue that is approved for treatment of chronic hepatitis B. Adefovir dipivoxil is associated with proximal tubular dysfunction, resulting in Fanconi syndrome, which can cause secondary hypophosphatemic osteomalacia. We describe a case of a patient with hypophosphatemic osteomalacia secondary to Fanconi syndrome induced by adefovir dipivoxil concomitantly with osteoporosis in whom clinical symptoms were improved by adding denosumab (a human monoclonal antibody targeting the receptor activator of nuclear factor-κB ligand) to preceding administration of vitamin D 3 ., Case Presentation: A 60-year-old Japanese man had been receiving low-dose adefovir dipivoxil (10 mg/day) to treat chronic hepatitis B for approximately 5 years. He presented to an orthopedic surgeon with severe pain of the right hip and no trauma history, and fracture of the neck of the right femur was identified. In addition, 99m Tc-hydroxymethylene diphosphate scintigraphy revealed significantly abnormal uptake in the bilateral ribs, hips, and knees, and he was therefore referred to our university hospital for evaluation of multiple pathological fractures. We diagnosed hypophosphatemic osteomalacia due to Fanconi syndrome induced by adefovir dipivoxil therapy. Although we reduced the patient's adefovir dipivoxil dose and added calcitriol (active vitamin D 3 ), he did not respond and continued to complain of bone pain. Several bone resorption markers and bone-specific alkaline phosphatase were also persistently elevated. Therefore, we added denosumab to vitamin D 3 supplementation for treatment of excessive bone resorption. Two months after initiation of denosumab, his hip and knee pain was relieved, along with a decrease in serum alkaline phosphatase and some bone resorption markers., Conclusions: Although denosumab is not generally an appropriate treatment for acquired Fanconi syndrome, it may be useful for patients who have hypophosphatemic osteomalacia due to adefovir dipivoxil-induced Fanconi syndrome associated with excessive bone resorption. However, clinicians should keep in mind that if denosumab is administered to patients with hypophosphatemic osteomalacia accompanied by excessive bone resorption, adequate vitamin D and/or phosphate supplementation should be done before administration of denosumab.

A woman in her 60s visited our hospital due to elevation of ALP (1357U/L). The patient had been treated with lamivudine (LAM) in 2005, LAM+adefovir (ADV) in 2009, and ADV+entecavir in 2015 for chronic hepatitis B (CH-B). The ALP isozyme was predominantly bone type. Urinary β-2 microglobulin (MG) and α-1MG increased to 49635μg/L and 64.1mg/L, respectively. Though no fractures were found during bone scintigraphy, the patient was diagnosed with Fanconi syndrome. However, 3 months after switching from ADV to tenofovir alafenamide (TAF), ALP decreased to 856U/L, and urinary β-2MG and α-1MG decreased to 624μg/L and 6.0mg/L, respectively. Fanconi syndrome should be considered when an increase in ALP is observed in patients treated with ADV, and urinary β-2MG and α-1MG assays are useful for establishing a diagnosis. Switching from ADV to TAF was an effective therapeutic option.

Rationale: Renal Fanconi syndrome (FS) is a rare complication of monoclonal gammopathy. It is characterized by the impairment of renal proximal tubular function leading to normoglycemic glycosuria, aminoaciduria, hypophosphatemia, hypouricemia and proximal renal tubular acidosis. Renal impairment in monoclonal gammopathy, without fulfilling the criteria of multiple myeloma, is categorized as monoclonal gammopathy of renal significance (MGRS)., Patient Concerns: A 54-year-old male presented with progressively aggravated bone pain and limitation of activity was admitted to our department. A proximal renal tubular damage was suggested by hypophosphatemia, compensated metabolic acidosis, renal glycosuria, aminoaciduria, and hypouricemia. M-protein of IgA kappa was detected by immunofixation electrophoresis. Mildly increased plasma cells were found in bone marrow cytomorphologic examination. Renal biopsy revealed diffuse linear monoclonal IgA-kappa light chain deposits along tubular basement membranes (TBMs), while lambda was negative. Electron microscopy showed granular electron-dense deposits along the outer aspect of TBMs., Diagnoses: The patient was diagnosed as FS induced osteomalacia secondary to monoclonal gammopathy of renal significance (MGRS) (IgA-κ type) and LCDD., Interventions: He was treated with bortezomib, supplementation by phosphate, alkali agents, and active vitamin D. He responded well to the treatment symptomatically., Outcomes: We reported a rare case of adult acquired FS with hypophosphatemic osteomalacia secondary to LCDD associated with MGRS and the patient was successfully treated with bortezomib., Lessons: Although few cases of LCDD with isolated symptoms of tubulointerstitial nephropathy, rather than glomerular symptoms have been reported. It still needs to be recognized as a differential diagnosis in monoclonal gammopathy.

This article presents a case of cystinosis in a young man. Diagnosis of the disease and the problem of transition to adult care are described. Cystinosis is a rare lysosomal storage disease with first manifestation in early childhood presenting as renal Fanconi syndrome. Without treatment, the disease leads to severe health impairment. Due to the rarity of the disease, a correct diagnosis is often delayed. Without treatment, cystinosis often leads to end-stage renal failure, blindness, hypothyroidism, diabetes mellitus, and rickets. Cystine-depleting therapy with cysteamine significantly improves mortality and quality of life.

We herein report two cases of Fanconi syndrome with refractory hypophosphatemic osteomalacia that was difficult to correct by phosphorus replacement therapy. The pathological result was a bony giant cell tumor and osteosarcoma, respectively. Interestingly, after resection of the tumors, the patient with osteosarcoma recovered completely but the patient with the bony giant cell tumor had a relapse. Although she underwent nine operations, her symptoms and laboratory tests did not improve. These findings indicate that Fanconi syndrome can result from a bone tumor.

Proximal renal tubular acidosis (pRTA) is an inherited or acquired clinical syndrome in which there is a decreased bicarbonate reclamation in the proximal tubule resulting in normal anion gap hyperchloremic metabolic acidosis. In children, pRTA may be isolated but is often associated with a general proximal tubular dysfunction known as Fanconi syndrome which frequently heralds an underlying systemic disorder from which it arises. When accompanied by Fanconi syndrome, pRTA is characterized by additional renal wasting of phosphate, glucose, uric acid, and amino acids. The most common cause of inherited Fanconi syndrome in the pediatric age group is cystinosis, a disease with therapeutic implications. In this article, we summarize the clinical presentation and differential diagnosis of pRTA and Fanconi syndrome and provide a practical approach to their evaluation in children., (Copyright © 2018 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.)

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., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Ltd (unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Objectives: To summarize available clinical evidence for cysteamine bitartrate preparations in the treatment of nephropathic cystinosis as identified through a systematic literature review (SLR)., Methods: We searched MEDLINE, MEDLINE In-Process and Embase using Ovid with a predefined search strategy through 19 January 2016. All publicly available clinical reports on the use of delayed-release (DR) cysteamine bitartrate (Procysbi 1 ) or immediate-release (IR) cysteamine bitartrate (Cystagon 2 ) in patients with cystinosis were included., Results: We identified a total of 103 publications and 10 trial records. Of these, 9 studies describe DR cysteamine bitartrate (n = 267 patients), 42 describe IR cysteamine bitartrate (n = 1,427 patients) and in 53 studies the exact preparation was not specified (n = 906 patients). The vast majority of the studies used a non-randomized study design, with randomized clinical trials (RCTs) being scarce (1 study comparing DR and IR formulation) and case reports (n = 49) being the most common study design representing 47% of the total., Conclusion: A substantial evidence base for cysteamine bitartrate in the treatment of nephropathic cystinosis was identified. However, the majority of the evidence was of relatively low quality, with evidence levels of 3 or 4.

Background: Cystinosis is a rare autosomal recessive lysosomal disorder characterized by the accumulation of cystine in lysosomes. Cystinosis is much rarer in Asian than Caucasian populations. There are only 14 patients have with cystinosis alive in Japan. Most cystinosis is the nephropathic infantile form, as indicated by its apparent and severe clinical manifestations, including renal and ocular symptoms. Patients with the nephropathic juvenile form account for 5% of those with cystinosis. Their diagnosis is frequently delayed and difficult because of slower progression to end-stage renal disease and fewer cystine crystals in the cornea. Molecular analysis and a cysteine-binding protein assay should be performed when patients with proximal tubulopathy of an unknown origin are encountered., Case Presentation: A 12-year-old boy had been suffering from Fanconi syndrome since he was 3 years old. He was only recently diagnosed despite repeated ophthalmological examinations. Corneal cystine crystals were found when he was 12 years old, and he was diagnosed with cystinosis by high free cystine content in granulocytes (6.36 nmol half-cystine/mg protein, normal: <0.15). Analysis of the CTNS gene showed two novel heterozygous single nucleotide substitutions of c.329G > C and c.329 + 2 T > C. Both were splicing site variants causing exon 6 skipping proven by transcript analysis, although the functional prediction site showed c.329G > C, p.(Gly110Ala) as a benign missense substitution. The patient's estimated glomerular filtration rate was 66.8 mL/min/1.73 m 2 . He was immediately treated with cysteamine after diagnosis., Conclusions: Even if no ophthalmological abnormalities are present, nephropathic juvenile cystinosis should be suspected in children with Fanconi syndrome. Transcript analysis was useful to detect pathogenic splicing variants in this patient.

A 77-year-old female with renal dysfunction, hypercalcemia, and hypercalciuria was presented. Systemic investigations including renal biopsy showed that the patient had Fanconi syndrome secondary to renal sarcoidosis. Treatment with 25 mg per day of prednisolone was initiated and her condition improved. Complication of Fanconi syndrome in patients with sarcoidosis is extremely rare. Although the pathological mechanism is still unknown, corticosteroid therapy was effective for ameliorating proteinuria, glycosuria, hypercalciuria, and aminoaciduria.

Case Series Summary: Fanconi syndrome (FS) is well described in humans and dogs, but has not been reported in cats. This case series describes four cats with acquired FS. On the basis of clinical signs and intestinal biopsies, all cats were initially diagnosed with alimentary lymphoma or inflammatory bowel disease. Treatment with chlorambucil and corticosteroids was started at standard doses, based on published protocols. Within 2-26 months of the start of treatment, glucosuria, despite normoglycemia, was identified incidentally on routine biochemical screening; FS was diagnosed with urine metabolic assays, confirming aminoaciduria and glucosuria in all four cases. Neither polyuria nor polydipsia were noted in any case, and only 1/4 cats had any clinical signs at the time of diagnosis. Partial or complete resolution of FS was seen in 3/4 cases within 3 months of discontinuing chlorambucil therapy., Relevance and Novel Information: This is the first case series to document acquired FS in the cat, and the first to suggest a possible association between chlorambucil and acquired FS. Cats treated with chlorambucil should be monitored for the development of glucosuria, and discontinuation of chlorambucil should be considered if FS is identified. Further study into the association between chlorambucil and acquired FS in cats is warranted., (© The Author(s) 2015.)

Nephropathic cystinosis is an autosomal recessive metabolic, lifelong disease characterized by lysosomal cystine accumulation throughout the body that commonly presents in infancy with a renal Fanconi syndrome and, if untreated, leads to end-stage kidney disease (ESKD) in the later childhood years. The molecular basis is due to mutations in CTNS, the gene encoding for the lysosomal cystine-proton cotransporter, cystinosin. During adolescence and adulthood, extrarenal manifestations of cystinosis develop and require multidisciplinary care. Despite substantial improvement in prognosis due to cystine-depleting therapy with cysteamine, no cure of the disease is currently available. Kidney Disease: Improving Global Outcomes (KDIGO) convened a Controversies Conference on cystinosis to review the state-of-the-art knowledge and to address areas of controversies in pathophysiology, diagnostics, monitoring, and treatment in different age groups. More importantly, promising areas of investigation that may lead to optimal outcomes for patients afflicted with this lifelong, systemic disease were discussed with a research agenda proposed for the future., (Copyright © 2016 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

In a case of acquired Fanconi syndrome associated with smoldering myeloma, we confirmed the deposition of protease-resistant κ light chain proteins in a proximal tubular injury and found the decreased expression of apical tubular transporters including sodium glucose co-transporter, sodium phosphate co-transporter, uric acid transporter 1, and a decrease of Na(+)/K(+)-ATPase in the basolateral membrane. The protease-resistant kappa light chain has a pathological role in the expression of tubular transporters in the proximal tubule and causes Fanconi syndrome associated with smoldering myeloma.

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.

Background: The p.R63W mutation in the hepatocyte nuclear factor-4 alpha (HNF4A) results in macrosomia and atypical Fanconi syndrome, in addition to hyperinsulinaemic hypoglycaemia (HI). We describe 2 infants carrying this mutation, presenting with additional features. Cases Series: Patient 1, a male born with a birth weight of 1.7 SDS, was diagnosed with HI on day 2 of life. He responded to 3-10 mg/kg/day of diazoxide. Raised serum creatinine led to the investigation of renal tubular function, showing leaking of electrolytes and protein. The patient also had conjugated hyperbilirubinaemia with liver steatosis. Patient 2 was a male born with a weight of 0.36 SDS. His mother had renal Fanconi syndrome. He received parenteral nutrition and presented with HI at 1 month of age, while establishing enteral feeds. Biochemistry workup showed renal tubular leaking of calcium, sodium, and phosphate. A hypoglycaemia screen documented HI, and the patient was commenced on 2 mg/kg/day of diazoxide. Continuous glucose monitoring was performed in his mother, revealing overnight hypoglycaemia., Conclusion: Renal Fanconi syndrome represents the only HNF4A feature showing complete penetrance. Our cases suggest that the p.R63W HNF4A mutation must be considered in subjects with a normal birth weight and postulate the possibility of liver involvement as a part of this condition., (© 2016 S. Karger AG, Basel.)

Background and Objectives: Nephropathic cystinosis is a lysosomal storage disorder characterized by renal tubular Fanconi syndrome in infancy and glomerular damage leading to renal failure at ∼10 years of age. Therapy with the cystine-depleting agent cysteamine postpones renal failure, but the degree of compliance with this treatment has not been correlated with preservation of kidney function., Methods: We assessed leucocyte cystine depletion by cysteamine and created the composite compliance score that incorporates the extent of leucocyte cystine depletion, as well as duration of cysteamine treatment, into a single integer. Age at renal failure was used to gauge preservation of renal function, and the Fanconi syndrome index (FSI), a measure of aminoaciduria, was used to assess renal tubular Fanconi syndrome., Results: Age at renal failure varied directly and linearly with the composite compliance score (y = 0.3x +8.8; R(2) = 0.61). The slope indicated that for every year of excellent cystine depletion, nearly 1 year of renal function was preserved. Age at renal failure correlated roughly with mean leucocyte cystine level, but not with mean cysteamine dosage. There was no correlation between the FSI and the composite compliance score., Conclusions: Greater compliance with oral cysteamine therapy yields greater preservation of renal glomerular, but not tubular, function. Oral cysteamine therapy should be given at the maximum tolerated dose, within the recommended limits.

Fanconi syndrome is a complex of multiple tubular dysfunctions of proximal tubular cells, occurring alone or in association with a variety of inherited (primary) or acquired (secondary) disorders. It is characterized by aminoaciduria, normoglycemic glycosuria, tubular proteinuria without hematuria, metabolic acidosis without anion gap and excessive urinary excretion of phosphorous, calcium, uric acid, bicarbonate, sodium, potassium and magnesium. Diabetes insipidus is a disease of collecting tubules and children mainly present with dehydration and hypernatremia. We are reporting the first case of idiopathic Fanconi's syndrome along with nephrogenic diabetes insipidus in a child who presented to us with vitamin D resistant rickets. Medline search did not reveal any case of nephrogenic diabetes insipidus (NDI) associated with idiopathic Fanconi syndrome. We hypothesized that the NDI may be due to to severe hypokalemia induced tubular dysfunction.

Objectives: To assess whether copper deficiency plays a role in the recently described cysteamine toxicity in patients with cystinosis, and to examine whether polymorphisms in copper transporters, lysyl oxidase, and/or type I procollagen genes could be responsible for the occurrence of cysteamine toxicity in a small subset of patients with cystinosis., Study Design: Thirty-six patients with cystinosis were included: 22 with Fanconi syndrome (including 7 with cysteamine toxicity), 12 after renal transplantation, 1 receiving hemodialysis, and 1 with ocular cystinosis. Serum copper and ceruloplasmin levels and urinary copper/creatinine ratio were measured. Genes ATP7A and CTR1 (encoding copper transporters), LOX (encoding lysyl oxidase), and COL1A1 and COL1A2 (encoding type I procollagen) were analyzed in patients with (n = 6) and without (n = 5) toxicity. Fibroblast (pro)collagen synthesis was compared in patients with (n = 3) and those without (n = 2) cysteamine toxicity., Results: All 22 patients with Fanconi syndrome had increased urinary copper excretion. Serum copper and ceruloplasmin levels were decreased in 9 patients, including all 7 patients with cysteamine toxicity. No specific sequence variations were associated with toxicity. All fibroblasts exhibited normal (pro)collagen synthesis., Conclusion: Patients with cystinosis with cysteamine toxicity demonstrate copper deficiency. This can cause decreased activity of lysyl oxidase, the enzyme that generates the aldehydes required for collagen cross-linking. Thus, copper supplementation might prevent cysteamine toxicity., (Copyright © 2013 Mosby, Inc. All rights reserved.)

Objective: To determine whether early treatment with cysteamine affects cognitive functioning in patients with nephropathic cystinosis., Study Design: Forty-six subjects aged 3-18 years with cystinosis underwent cognitive testing to determine intelligence, visual-spatial abilities, and visual-motor skills. An age-matched control group (n = 85; age 2-22 years) underwent the same tests. Age at diagnosis and age at initiation of treatment with cysteamine were recorded at the time of testing., Results: Patients with cystinosis treated at or after age 2 years (late-treatment group) scored significantly lower on verbal, performance, and full-scale IQ measures, as well as on a test of visual-spatial skills, compared with patients treated before age 2 years (early-treatment group) and controls. Both groups of subjects with cystinosis demonstrated impaired visual-motor skills compared with controls, with no difference between the early-treatment and late-treatment groups., Conclusion: Early treatment with cysteamine appears to improve intellectual function in patients with nephropathic cystinosis. However, the lack of improvement in visual-motor function with early cysteamine treatment suggests possibly different mechanisms underlying visual-motor performance compared with other areas of cognition in this disorder., (Copyright © 2013 Mosby, Inc. All rights reserved.)