Search

Numerous health concerns, primarily kidney injury, have been reported with the use of Beni-kōji CholesteHelp, a functional food containing red yeast rice. Here, we describe 2 cases of kidney injury caused by beni-kōji. The first case had normal kidney function before consuming the product. After several months of use, she developed hypertension. After 6 months of supplement consumption, her estimated glomerular filtration rate (eGFR) dropped to 22.5 mL/min/1.73 m2. A spot urine sample showed a urinary protein-to-creatinine ratio of 2.03 g/g, leading to the diagnosis of Fanconi syndrome. Kidney biopsy showed tubular degeneration. Thirty-five days after discontinuing the supplement, proteinuria resolved and the eGFR returned to baseline level. The second case, who had diabetes and normal kidney function, experienced severe kidney injury (eGFR, 3.5 mL/min/1.73 m2) after 4 months of Beni-kōji CholesteHelp use. He required hemodialysis for >2 weeks but recovered kidney function after the product was discontinued. Kidney biopsy showed tubular injury similar to the first case and glomeruli changes consistent with diabetic nephropathy. These cases indicate that beni-kōji use is associated with tubular toxicity. Further studies are required to identify the precise etiology and mechanism of kidney injury.

Light-chain proximal tubulopathy (LCPT) is typically characterized by the intracytoplasmic deposition of light chains within the proximal tubular epithelial cells, which is usually classified into crystalline and noncrystalline subgroups. Membranous nephropathy (MN) is a common glomerular disease characterized by diffused subepithelial electron-dense deposits along the capillary loop accompanied by the effacement and microvillus transformation of the foot process. Here, we report a biopsy-confirmed case of a concurrence of LCPT with crystals (κ light chains restricted) and antigen-undetermined MN in a male patient. The patient presented with low-molecular-weight proteinuria, increased serum creatinine levels, and incomplete Fanconi syndrome. To our knowledge, this is the first report of a concurrence of LCPT and independent MN of unknown target antigens, which may enrich our recognition of monoclonal gammopathy of renal significance with synchronous MN.

Microtubules are cytoskeletal polymers of ⍺/β-tubulin heterodimers essential for a wide range of cellular processes. Pathogenic variations in microtubule-encoding genes (e.g., TUBB4B, which encodes the β-4B tubulin isotype) are responsible for a wide spectrum of cerebral malformations, collectively referred to as “tubulinopathies.” The phenotypic manifestation of TUBB4B-associated tubulinopathy is Leber congenital amaurosis with early-onset deafness (LCAEOD), an autosomal dominant syndrome characterized by photoreceptor and cochlear cell loss; all known patients have pathogenic variations in amino acid R391. We present the clinical and molecular genetics findings of a 16-year-old female with a de novo missense variant in exon 1 of TUBB4B, c.32 A > G (p.Gln11Arg; Q11R). In addition to hearing loss and hyperopia without retinal abnormalities, our proband presented with two phenotypes of unknown genetic etiology, i.e., renal tubular Fanconi Syndrome (FS) and hypophosphatemic rickets (HR). The Q11R variant expands the genetic basis of early sensory hearing loss; its consequences with respect to microtubule structure are described. A mechanistic explanation for the FS and rickets, involving microtubule-mediated translocation of transporter proteins to and from the apical membrane of renal proximal tubular cells, is proposed.

Background: Tenofovir is an effective drug in the treatment of chronic hepatitis B. However, it has been associated with adverse complication of Fanconi syndrome due to proximal renal tubule dysfunction. This leads to severe hypophosphatemia and osteomalacia which predisposed patients to fragility fractures. Case report: Here, we report the case of a 67-year old man on tenofovir for chronic hepatitis B, presenting with bilateral atraumatic neck of femur (NOF) fractures. Bone mineral density (BMD) scan of the lumbar spine revealed a low T-score of −2.6. Laboratory studies revealed severe hypophosphatemia and hypocalcemia and high alkaline phosphate concentration. A diagnosis of tenofovir-induced Fanconi syndrome was made. Tenofovir was replaced with entecavir and after appropriate optimization with the help of endocrinologist, he underwent a total hip replacement via a direct anterior approach of the more symptomatic left hip. At 1-month post-operation, he was asymptomatic and ambulating well. Conclusion: High index of suspicion and early identification of Fanconi syndrome is required in bilateral atraumatic neck of femur fractures to treat the underlying disorder while planning for surgical intervention. Treatment of NOF fractures in patients with Fanconi syndrome should be a total hip replacement after discontinuing tenofovir and subsequent correction of any electrolyte abnormalities.

Monoclonal Ig crystalline nephropathies are rare lesions resulting from precipitation of monoclonal Igs in the kidney as crystalline inclusions. They can be categorized into lesions with predominant intracellular crystals (light chain [LC] proximal tubulopathy, LC crystal-storing histiocytosis, and LC crystalline podocytopathy) and lesions with predominant extracellular crystals (crystalglobulin-induced nephropathy and crystalline variant of LC cast nephropathy). The majority of these lesions are associated with low tumor burden lymphoproliferative disorders, with the exception of crystalline variant of LC cast nephropathy. Extrarenal involvement (e.g., skin and cornea) is frequent. Kidney biopsy is the cornerstone for diagnosis, which often requires electron microscopy and antigen retrieval. A thorough hematologic workup and evaluation of extrarenal involvement is mandatory for management. Treatment of these lesions is with clone-directed therapy, with the goal of achieving hematologic very good partial response or complete response, which preserves or improves kidney function. In vitro and in vivo studies, animal models, and novel sequencing techniques have been invaluable tools to understand the pathogenesis of LC proximal tubulopathy and can be used to increase our limited knowledge of the pathogenesis of the other monoclonal Ig crystalline nephropathies. This review provides an update on the pathology, renal and hematologic characteristics, extrarenal manifestations, prognosis, treatment, and pathogenesis of monoclonal Ig crystalline nephropathies., (Copyright © 2024 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Objective: Previous studies have shown that patients with hereditary fructose intolerance (HFI) are characterized by a greater intrahepatic triglyceride content, despite a fructose-restricted diet. The present study aimed to examine the long-term consequences of HFI on other aldolase-B-expressing organs, i.e. the kidney and vascular endothelium.Methods: Fifteen adult HFI patients were compared to healthy control individuals matched for age, sex and body mass index. Aortic stiffness was assessed by carotid-femoral pulse wave velocity (cf-PWV) and endothelial function by peripheral arterial tonometry, skin laser doppler flowmetry and the endothelial function biomarkers soluble E-selectin [sE-selectin] and von Willebrand factor. Serum creatinine and cystatin C were measured to estimate the glomerular filtration rate (eGFR). Urinary glucose and amino acid excretion and the ratio of tubular maximum reabsorption of phosphate to GFR (TmP/GFR) were determined as measures of proximal tubular function. Results: Median systolic blood pressure was significantly higher in HFI patients (127 versus 122 mmHg, p = .045). Pulse pressure and cf-PWV did not differ between the groups (p = .37 and p = .49, respectively). Of all endothelial function markers, only sE-selectin was significantly higher in HFI patients (p = .004). eGFR was significantly higher in HFI patients than healthy controls (119 versus 104 ml/min/1.73m2, p = .001, respectively). All measurements of proximal tubular function did not differ significantly between the groups.Conclusions: Adult HFI patients treated with a fructose-restricted diet are characterized by a higher sE-selectin level and slightly higher systolic blood pressure, which in time could contribute to a greater cardiovascular risk. The exact cause and, hence, clinical consequences of the higher eGFR in HFI patients, deserves further study.

Phosphate is an integral part of human cellular structure and function. Though most recognised disorders of phosphaturia are genetic in origin, phosphate loss due to acquired conditions is commonly encountered in clinical practice. Acquired hypophosphatemia is most commonly due to renal phosphate wasting and can produce significant morbidity. It also heralds future kidney damage, and continued exposure can lead to progressive kidney injury and potentially renal failure. These conditions are a diverse group of disorders with common shared mechanisms causing loss of phosphate in the urine. Renal phosphate loss can occur as an isolated entity or as a part of generalised proximal tubular dysfunction, i.e., Fanconi's syndrome. An insight into the pathophysiological mechanisms of acquired phosphaturia can help clinicians monitor their patients better and avoid potential harms., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Introduction: Cystinosis is a rare systemic lysosomal storage disease that mainly affects the kidney and the eye. Renal replacement therapy is started in patients with cystinosis during the first decade of life in the absence of treatment. The prognosis of cystinosis depends on early diagnosis and the prompt start of and good compliance with cysteamine treatment. Kidney disease progression, extra-renal complications and shorter life expectancy are more pronounced in patients who do not adhere to treatment. Objective: The aim of this work was to establish recommendations for the comprehensive care of cystinosis and facilitate patient transition from paediatric to adult medicine, based on clinical experience. The goal is to reduce the impact of the disease and improve prognosis and patient quality of life. Methods: Bibliographic research and consensus meetings with a multidisciplinary professional team of clinical experts in cystinosis (T-CiS.bcn group) from 5 hospitals in Barcelona. Results: This consensus document gathers specific recommendations for the diagnosis, treatment and multidisciplinary care of cystinotic patients in the following areas: nephrology, dialysis, kidney transplantation, ophthalmology, endocrinology, neurology, laboratory, genetic counselling, nursing and pharmacy. Conclusions: Guidelines for the comprehensive care of cystinosis provide a support tool for health professionals who look after these patients. They are based on the following main pillars: (a) a multidisciplinary approach; (b) appropriate disease monitoring and control of white blood cell (WBC) cystine levels; (c) the importance of adherence to cysteamine treatment; and (d) the promotion of patient self-care by means of disease education programmes. All these recommendations will lead us, in a second phase, to create a coordinated model of transition from paediatric to adult care services which will cover the specific needs of cystinosis.

Mitochondrial DNA (mtDNA) deletion is a rare occurrence that results in defects to oxidative phosphorylation. The common clinical presentations of mtDNA deletion vary but include mitochondrial myopathy, Pearson syndrome, Kearns-Sayre syndrome, and progressive external ophthalmoplegia. Here, we report the case of a 10-year-old boy who presented with progressive deterioration of his clinical status (which included hypoglycemia, short stature, sensorineural hearing loss, retinitis pigmentosa, and chronic gastrointestinal dysmotility) that progressed to acute deterioration with pancreatitis, Fanconi syndrome, lactic acidosis, and acute encephalopathy. Following treatment, the patient was stabilized and his neurological condition improved. Through a combination of histological examinations and biochemical and molecular analyses, mitochondrial disease was confirmed. A novel 3670-base pair deletion (deletion of mtDNA nt 7,628-11,297) was identified in the muscle tissue. A direct repeat of CTACT at the breakpoints was also detected.

Nephropathic cystinosis is a rare disease secondary to recessive mutations of the CTNS gene encoding the lysosomal cystine transporter cystinosin, causing accumulation of cystine in multiple organs. Over the years, the disease has evolved from being a fatal condition during early childhood into a treatable condition, with patients surviving into adulthood. Data on cystinosis are limited by the rarity of the disease. Here, we have investigated factors associated with kidney and growth outcome in a very large cohort of 453 patients born between 1964 and 2016 and followed in Belgium, Germany, Austria, France, Italy, Spain, The Netherlands, Turkey and United Kingdom. From the 1970s to the 1990s, the median increase in kidney survival was 9.1 years. During these years, cysteamine, a cystine-depleting agent, was introduced for the treatment of cystinosis. Significant risk factors associated with early progression to end-stage kidney disease assessed by Cox proportional multivariable analysis included delayed initiation of cysteamine therapy and higher mean leucocyte cystine levels. No significant effect on kidney function was observed for gender, pathogenic variant of the CTNS gene, and the prescription of indomethacin or renin angiotensin system blockers. Significantly improved linear growth was associated with early use of cysteamine and lower leukocyte cystine levels. Thus, our study provides strong evidence in favor of early diagnosis and optimization of cystine depletion therapy in nephropathic cystinosis., (Copyright © 2021 International Society of Nephrology. All rights reserved.)

Recessive mutations in the glucose transporter gene SLC2A2 (GLUT2) lead to permanent neonatal diabetes (PNDM) and Fanconi Bickel Syndrome (FBS). Here, we generated an induced pluripotent stem cell (iPSC) line, QBRIi012-A, from a 24-month-old boy with FBS and PNDM due to homozygous nonsense mutation in the SLC2A2 gene (c.901C > T). The QBRIi012-A was fully characterized using different approaches. The cell line showed normal karyotype and was able to differentiate into the three germ layers in vitro. This iPSC line provides a novel human cell model to understand the pathophysiology of FBS and diabetes associated with SLC2A2 defects., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

The main clinical features of tyrosinemia type 1 usually appear in the first months of life, including fever, diarrhea, vomiting, liver involvement, growth failure, and renal proximal tubulopathy with subsequent hypophosphatemic rickets. An early diagnosis is crucial in order to provide specific management and to prevent complications. Here, we report on two cases referred primarily to pediatric nephrologists for the diagnosis of "neonatal tubulopathy" and management of "X-linked hypophosphatemia (XLH)," respectively. Our aim is to emphasize that (1) even a mixed tubulopathy can reveal tyrosinemia, and (2) tyrosinemia is a classic differential diagnosis of XLH that should not be forgotten, especially in the era of the anti-FGF23 burosumab., (Copyright © 2021 French Society of Pediatrics. Published by Elsevier Masson SAS. All rights reserved.)

Plasma and B cells dyscrasias that overproduce monoclonal immunoglobulin free light chains (FLCs) affect the kidney frequently in various ways. The hematologic dyscrasia responsible for the production of FLCs may or may not meet the criteria for cancer, such as multiple myeloma (MM) or lymphoma, or may remain subclinical. If there is overt malignancy, the accompanying kidney disorder is called myeloma- or lymphoma-associated. If the dyscrasia is subclinical, the associated kidney disorders are grouped as monoclonal gammopathy of renal significance. Glomeruli and tubules may both be involved. The proximal tubule disorders comprise a spectrum of interesting syndromes, which range in severity. This review focuses on the recent insights gained into the patterns and the mechanisms of proximal tubule toxicity of FLCs, including subtle transport disorders, such as proximal tubule acidosis, partial or complete Fanconi syndrome, or severe acute or chronic renal failure. Histologically, there may be crystal deposition in the proximal tubule cells, acute tubule injury, interstitial inflammation, fibrosis, and tubule atrophy. Specific structural alterations in the V domain of FLCs caused by somatic hypermutations are responsible for crystal formation as well as partial or complete Fanconi syndrome. Besides crystal formation, tubulointerstitial inflammation and proximal tubulopathy can be mediated by direct activation of inflammatory pathways through cytokines and Toll-like receptors due to cell stress responses induced by excessive FLC endocytosis into the proximal tubule cells. Therapy directed against the clonal source of the toxic light chain can prevent progression to more severe lesions and may help preserve kidney function.

Fanconi Bickel Syndrome (FBS) is an autosomal recessive disease resulting from mutations in the SLC2A2 gene, encoding the GLUT2. FBS patients develop diabetes mellitus. Using non-integrating Sendai virus, we generated an induced pluripotent stem cell (iPSC) line, QBRIi007-A, carrying the c.613-7 T>G homozygous mutation in intron 5 of the SLC2A2 gene from a 19-year-old female with FBS and diabetes. The iPSC line was characterized for pluripotency, differentiation potential, genomic integrity, and genetic identity. This iPSC line provides a useful cell model to understand the role of GLUT2 in the disease development and to discover new drug candidates., (Copyright © 2020 The Author(s). Published by Elsevier B.V. All rights reserved.)

Background: The leading cause of death in patients with Fukuyama congenital muscular dystrophy (FCMD) is congestive heart failure or respiratory dysfunction, which is same as that in Duchenne muscular dystrophy (DMD). Recent studies reported that renal dysfunction is a common complication and an increasing cause of death in advanced DMD. It can be attributable to circulatory instability or inappropriate use of drugs for treating cardiac dysfunction., Methods: We retrospectively evaluated renal function in 38 genetically diagnosed patients with FCMD (range, 1.3-32.9 years; mean age, 13.7 ± 6.9 years) using cystatin C. We examined possible relationships of cystatin C with blood natriuretic peptide and creatinine levels along with cardiac echocardiography findings., Results: Twenty-five patients were treated for cardiac dysfunction. Elevated cystatin C level was detected only in two, who also showed proteinuria, glycosuria, hematuria, and extremely high β2-microglobulin levels on urine tests, and were thus diagnosed with renal tubular cell damage. Because both patients were treated for intractable epilepsy with various antiepileptic drugs, including valproic acid (VPA), and had low serum carnitine levels, renal tubular cell damage was considered as an adverse effect of VPA. Unlike patients with DMD, no patient with FCMD had renal dysfunction. Such a rare occurrence of renal dysfunction can be attributable to mild cardiac dysfunction, short disease duration, and careful and early fluid management., Conclusion: Renal dysfunction is rare in patients with FCMD; however, renal tubular cell damage should be ascertained, particularly in those undergoing VPA treatment for epilepsy., (Copyright © 2018 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.)

The microvillus brush border on the renal proximal tubule epithelium allows the controlled reabsorption of solutes that are filtered through the glomerulus and thus participates in general body homeostasis. Here, using the lipid 5-phosphatase Ship2 global knockout mice, proximal tubule-specific Ship2 knockout mice, and a proximal tubule cell model in which SHIP2 is inactivated, we show that SHIP2 is a negative regulator of microvilli formation, thereby controlling solute reabsorption by the proximal tubule. We found increased PtdIns(4,5)P2 substrate and decreased PtdIns4P product when SHIP2 was inactivated, associated with hyperactivated ezrin/radixin/moesin proteins and increased Rho-GTP. Thus, inactivation of SHIP2 leads to increased microvilli formation and solute reabsorption by the renal proximal tubule. This may represent an innovative therapeutic target for renal Fanconi syndrome characterized by decreased reabsorption of solutes by this nephron segment., (Copyright © 2017 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Studies in mice have suggested bone marrow transplantation as a strategy to correct the endocytic dysfunction of the proximal tubules in renal Fanconi syndrome, yet the mode of action has remained mysterious. Using a mouse model of Dent disease, Gabriel et al. now show that rescue of the resorptive capacity in the diseased kidney involves cell-to-cell contact between engrafted and host cells via nanotubes, cellular projections that enable transfer of wild-type activity into mutant cells of the proximal tubule., (Copyright © 2017 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Despite substantial progress in the development of antiretroviral regimens that durably suppress Human Immunodeficiency Virus (HIV) infection, new agents that maintain high efficacy while further optimizing the safety of lifelong, chronic therapy are needed. Tenofovir alafenamide (TAF; formerly known as GS-7340) is a novel prodrug of the antiviral acyclic nucleoside phosphonate tenofovir (TFV) with improved properties relative to tenofovir disoproxil fumarate (TDF). Although potent and generally well tolerated, TDF therapy has been associated with changes in markers of renal function, decreases in bone mineral density and a rare occurrence of serious renal adverse events, including Fanconi's Syndrome. The renal and bone toxicity observed with TDF is associated with high circulating plasma levels of TFV. TAF was discovered to be a more efficient prodrug able to further refine HIV therapy and better address life-long therapy in an older and increasingly comorbid HIV infected population. By enhancing stability in biological matrices while being rapidly activated in cells, TAF produces higher levels of intracellular TFV diphosphate, the pharmacologically active metabolite, in HIV-target cells at substantially reduced oral doses of TFV equivalents. All TFV released in the body is eventually eliminated renally; therefore, lowering the TFV equivalents administered reduces off-target kidney exposure. Effective therapy is thus achieved at approximately 90% lower systemic exposure to TFV, translating to statistically and clinically significant improvement in safety parameters associated with bone mineral density and markers of renal function., (Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.)

Proximal tubule protein uptake is mediated by 2 receptors, megalin and cubilin. These receptors rescue a variety of filtered ligands, including biomarkers, essential vitamins, and hormones. Receptor gene knockout animal models have identified important functions of the receptors and have established their essential role in modulating urinary protein excretion. Rare genetic syndromes associated with dysfunction of these receptors have been identified and characterized, providing additional information on the importance of these receptors in humans. Using various disease models in combination with receptor gene knockout, the implications of receptor dysfunction in acute and chronic kidney injury have been explored and have pointed to potential new roles of these receptors. Based on data from animal models, this paper will review current knowledge on proximal tubule endocytic receptor function and regulation, and their role in renal development, protein reabsorption, albumin uptake, and normal renal physiology. These findings have implications for the pathophysiology and diagnosis of proteinuric renal diseases. We will examine the limitations of the different models and compare the findings to phenotypic observations in inherited human disorders associated with receptor dysfunction. Furthermore, evidence from receptor knockout mouse models as well as human observations suggesting a role of protein receptors for renal disease will be discussed in light of conditions such as chronic kidney disease, diabetes, and hypertension., (Copyright © 2016 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Aim: To describe the characteristics of hypophosphatemia in severely disabled individuals with neurological disorders and to identify its causative factors., Method: We retrospectively reviewed clinical data from 82 individuals with motor skills classified as sitting, rollover or bedridden. Age, gender and body mass index were compared in individuals with (n=19) and without (n=63) a history of hypophosphatemia (serum phosphate levels <2.0 mg/dl). The clinical course of each patient with hypophosphatemia was reviewed and the cause identified. Laboratory data during hypophosphatemia was compared with that after recovery., Results: The age, gender and body mass index did not differ significantly between the individuals with and without hypophosphatemia. Nineteen patients experienced 25 episodes of hypophosphatemia. The causes included febrile illnesses (n=17), refeeding syndrome (n=4) and Fanconi syndrome (n=3), but was unidentifiable in one episode. Significant elevations in C-reactive protein levels and reductions in sodium levels were observed during hypophosphatemia episodes., Interpretation: Hypophosphatemia is a common complication in severely disabled individuals with frequent bacterial infections, refeeding following malnutrition and valproate administration for epilepsy treatment. Because severe hypophosphatemia is life threatening, serum phosphate levels should be closely monitored in this population., (Copyright © 2013 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.)

In Gaucher disease (GD), enzyme replacement therapy (ERT) results in the alleviation of hematological abnormalities and visceral infiltration as well as improvement in quality of life and life-span. However, several years may be required for skeletal manifestations, which are usually observed in type 1 and 3 GD, to respond to ERT. Infants with type 2 GD rarely present skeletal manifestations because most of these patients die within the first 2 years of life before they develop skeletal involvement. The use of ERT may prolong the lifespan of these patients and influence the natural history of the disease. The present study reports a new natural history of treated GD in which a 2-year and 7-month-old girl with type 2 GD who was receiving ERT developed valproate-induced Fanconi syndrome, pathological fractures, and pyogenic osteomyelitis. In conclusion, skeletal disease may occur in any type of GD, and Fanconi syndrome may lead to severe skeletal complications in patients with GD., (Copyright © 2013 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.)

Nephropathic cystinosis is a multisystem autosomal recessive disease caused by cystine accumulation, which is usually treated by oral cysteamine. In order to determine long-term effects of this therapy, we enrolled 86 adult patients (mean age 26.7 years) diagnosed with nephropathic cystinosis, 75 of whom received cysteamine. Therapy was initiated at a mean age of 9.9 years with a mean duration of 17.4 years. By last follow-up, 78 patients had end-stage renal disease (mean age 11.1 years), 62 had hypothyroidism (mean age 13.4), 48 developed diabetes (mean age 17.1 years), and 32 had neuromuscular disorders (mean age 23.3 years). Initiating cysteamine therapy before 5 years of age significantly decreased the incidence and delayed the onset of end-stage renal disease, and significantly delayed the onset of hypothyroidism, diabetes, and neuromuscular disorders. The development of diabetes and hypothyroidism was still significantly delayed, however, in patients in whom therapy was initiated after 5 years of age, compared with untreated patients. The life expectancy was significantly improved in cysteamine-treated versus untreated patients. Thus, cysteamine decreases and delays the onset of complications and improves life expectancy in cystinosis. Hence, cysteamine therapy should be introduced as early as possible during childhood and maintained lifelong.

Nephropathic cystinosis is an autosomal recessive disorder caused by mutations in the CTNS gene [1], which encodes for a transporter (cystinosin) responsible for cystine efflux from lysosomes. In cystinotic renal proximal tubules (RPTs), the defect in cystinosin function results in reduced reabsorption of solutes by apical Na(+)/solute cotransport systems, including the Na(+)/phosphate (Pi) cotransport system [2]. However the underlying molecular mechanisms are unknown, given the lack of an appropriate cellular model. To obtain such a model system, we have knocked down cystinosin with siRNA in primary RPT cell cultures. An 80% reduction in cystinosin strongly inhibited Na(+) dependent Pi uptake (70%). Although this finding could be explained by a direct effect on transporters as well as by altered energetics (the ATP level dropped by 52%), our results demonstrate a lack of involvement of Na, K-ATPase, and a reduction in the number of NaPi2a transporters., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Out of a series of 30 French patients with Pearson syndrome, we report on two patients with an atypical presentation, which include growth deficiency, pancytopaenia, tubulopathy and absence of exocrine pancreas dysfunction. Patient 1, a 4-year-old boy with a past history of pancytopaenia and transient metabolic acidosis at 13 months of age, presented at 2(1/2) years of age with severe tubulopathy of de Toni-Debré-Fanconi type, growth retardation, metabolic lactic acidosis and mild cytolysis. Despite normal exocrine pancreatic function, study of mitochondrial DNA revealed a 3.5 kb deletion. Patient 2 had a personal history of pancytopaenia requiring blood transfusions at 11 months of age and presented with severe intractable proximal and distal tubulopathy at 2 years of age. Exocrine pancreatic deficiency could not be evidenced and post-mortem studies revealed a 4.9 kb deletion of the mitochondrial DNA. A review of the literature revealed three patients presenting with Pearson syndrome and tubulopathy with normal pancreatic function and highlights delay in diagnosis in those three patients. The series of 30 French patients with Pearson syndrome also revealed that tubulopathy was present in 7/30 cases (23%), with variable outcome. In conclusion, Pearson syndrome should be screened for in children presenting with the association of growth retardation, anaemia/pancytopaenia, lactic acidosis and tubulopathy, even in the absence of exocrine pancreatic deficiency.