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Pediatric Nephrology (Berlin, Germany) Dec 2016The oculocerebrorenal syndrome of Lowe is a rare X-linked multisystemic disorder characterized by the triad of congenital cataracts, intellectual disability, and... (Review)
Review
The oculocerebrorenal syndrome of Lowe is a rare X-linked multisystemic disorder characterized by the triad of congenital cataracts, intellectual disability, and proximal renal tubular dysfunction. Whereas the ocular manifestations and severe muscular hypotonia are the typical first diagnostic clues apparent at birth, the manifestations of incomplete renal Fanconi syndrome are often recognized only later in life. Other characteristic features are progressive severe growth retardation and behavioral problems, with tantrums. Many patients develop a debilitating arthropathy. Treatment is symptomatic, and the life span rarely exceeds 40 years. The causative oculocerebrorenal syndrome of Lowe gene (OCRL) encodes the inositol polyphosphate 5-phosphatase OCRL-1. OCRL variants have not only been found in classic Lowe syndrome, but also in patients with a predominantly renal phenotype classified as Dent disease type 2 (Dent-2). Recent data indicate that there is a phenotypic continuum between Dent-2 disease and Lowe syndrome, suggesting that there are individual differences in the ability to compensate for the loss of enzyme function. Extensive research has demonstrated that OCRL-1 is involved in multiple intracellular processes involving endocytic trafficking and actin skeleton dynamics. This explains the multi-organ manifestations of the disease. Still, the mechanisms underlying the wide phenotypic spectrum are poorly understood, and we are far from a causative therapy. In this review, we provide an update on clinical and molecular genetic findings in Lowe syndrome and the cellular and physiological functions of OCRL-1.
Topics: Adolescent; Child; Child, Preschool; Chromosome Deletion; Chromosomes, Human, Pair 11; Humans; Infant; Infant, Newborn; Molecular Biology; Mutation; Oculocerebrorenal Syndrome; WAGR Syndrome
PubMed: 27011217
DOI: 10.1007/s00467-016-3343-3 -
Kidney International Reports May 2021Plasma and B cells dyscrasias that overproduce monoclonal immunoglobulin free light chains (FLCs) affect the kidney frequently in various ways. The hematologic dyscrasia... (Review)
Review
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.
PubMed: 34013100
DOI: 10.1016/j.ekir.2021.02.026 -
Journal of the American Society of... Jun 2021The transepithelial transport of electrolytes, solutes, and water in the kidney is a well-orchestrated process involving numerous membrane transport systems. Basolateral...
BACKGROUND
The transepithelial transport of electrolytes, solutes, and water in the kidney is a well-orchestrated process involving numerous membrane transport systems. Basolateral potassium channels in tubular cells not only mediate potassium recycling for proper Na,K-ATPase function but are also involved in potassium and pH sensing. Genetic defects in cause EAST/SeSAME syndrome, characterized by renal salt wasting with hypokalemic alkalosis associated with epilepsy, ataxia, and sensorineural deafness.
METHODS
A candidate gene approach and whole-exome sequencing determined the underlying genetic defect in eight patients with a novel disease phenotype comprising a hypokalemic tubulopathy with renal salt wasting, disturbed acid-base homeostasis, and sensorineural deafness. Electrophysiologic studies and surface expression experiments investigated the functional consequences of newly identified gene variants.
RESULTS
We identified mutations in the gene encoding KCNJ16, which along with KCNJ15 and KCNJ10, constitutes the major basolateral potassium channel of the proximal and distal tubules, respectively. Coexpression of mutant KCNJ16 together with KCNJ15 or KCNJ10 in oocytes significantly reduced currents.
CONCLUSIONS
Biallelic variants in were identified in patients with a novel disease phenotype comprising a variable proximal and distal tubulopathy associated with deafness. Variants affect the function of heteromeric potassium channels, disturbing proximal tubular bicarbonate handling as well as distal tubular salt reabsorption.
Topics: Acid-Base Imbalance; Adolescent; Adult; Alleles; Animals; Child, Preschool; Female; Hearing Loss, Sensorineural; Humans; Hypokalemia; Infant; Infant, Newborn; Kidney Diseases; Kidney Tubules; Loss of Function Mutation; Male; Mice; Nephrons; Oocytes; Pedigree; Phenotype; Potassium Channels, Inwardly Rectifying; RNA, Messenger; Renal Reabsorption; Salts; Exome Sequencing; Xenopus laevis; Young Adult
PubMed: 33811157
DOI: 10.1681/ASN.2020111587 -
Orphanet Journal of Rare Diseases May 2006Lowe syndrome (the oculocerebrorenal syndrome of Lowe, OCRL) is a multisystem disorder characterised by anomalies affecting the eye, the nervous system and the kidney.... (Review)
Review
Lowe syndrome (the oculocerebrorenal syndrome of Lowe, OCRL) is a multisystem disorder characterised by anomalies affecting the eye, the nervous system and the kidney. It is a uncommon, panethnic, X-linked disease, with estimated prevalence in the general population of approximately 1 in 500,000. Bilateral cataract and severe hypotonia are present at birth. In the subsequent weeks or months, a proximal renal tubulopathy (Fanconi-type) becomes evident and the ocular picture may be complicated by glaucoma and cheloids. Psychomotor retardation is evident in childhood, while behavioural problems prevail and renal complications arise in adolescence. The mutation of the gene OCRL1 localized at Xq26.1, coding for the enzyme phosphatidylinositol (4,5) bisphosphate 5 phosphatase, PtdIns (4,5)P2, in the trans-Golgi network is responsible for the disease. Both enzymatic and molecular testing are available for confirmation of the diagnosis and for prenatal detection of the disease. The treatment includes: cataract extraction, glaucoma control, physical and speech therapy, use of drugs to address behavioural problems, and correction of the tubular acidosis and the bone disease with the use of bicarbonate, phosphate, potassium and water. Life span rarely exceeds 40 years.
Topics: Adolescent; Adult; Central Nervous System Diseases; Child; Child, Preschool; Diagnosis, Differential; Eye Diseases; Female; Genetic Carrier Screening; Humans; Infant; Infant, Newborn; Kidney Diseases; Middle Aged; Oculocerebrorenal Syndrome; Phosphatidylinositols; Phosphoric Monoester Hydrolases; Pregnancy; Prenatal Diagnosis; Prognosis; Quality of Life; Young Adult
PubMed: 16722554
DOI: 10.1186/1750-1172-1-16 -
Nephrology, Dialysis, Transplantation :... Oct 2023Light chain proximal tubulopathy (LCPT) is a rare form of paraprotein-related disease, occurring in two main histopathological forms: crystalline and non-crystalline....
BACKGROUND
Light chain proximal tubulopathy (LCPT) is a rare form of paraprotein-related disease, occurring in two main histopathological forms: crystalline and non-crystalline. The clinicopathological features, treatment strategies and outcomes, especially of the non-crystalline form, are not well described.
METHODS
We conducted a single-centre retrospective case series of 12 LCPT patients, 5 crystalline and 7 non-crystalline, between 2005 and 2021.
RESULTS
The median age was 69.5 years (range 47-80). Ten patients presented with CKD and significant proteinuria (median estimated glomerular filtration rate of 43.5 ml/min/1.73 m2; urine protein:creatinine ratio 328 mg/mmol). Only six patients had known haematological disease at the time of renal biopsy. Multiple myeloma (MM) was diagnosed in seven patients cases and monoclonal gammopathy of renal significance (MGRS) in five patients. A clone was detected in all cases combining serum/urine electrophoresis and free light chain (LC) assays. Crystalline and non-crystalline variants had similar clinical presentations. For the non-crystalline variant, a diagnosis was reached based on a combination of CKD without another cause, haematological workup, LC restriction on immunofluorescence and abnormalities on electron microscopy (EM). Nine of 12 patients received clone-directed treatment. Patients who achieved haematological response (including all non-crystalline LCPT) had improved renal outcomes over a median follow-up of 79 months.
CONCLUSIONS
The non-crystalline variant may go unrecognised because of its subtle histopathological features and requires EM to distinguish it from 'excessive LC resorption without tubular injury'. Clone-directed treatment with good haematological response improves renal outcomes in both variants but limited data exist in MGRS. Multicentre prospective studies are needed to better define the clinicopathological characteristics associated with poor outcomes and optimize treatment strategies in patients with MGRS.
Topics: Humans; Middle Aged; Aged; Aged, 80 and over; Retrospective Studies; Kidney Diseases; Kidney; Multiple Myeloma; Immunoglobulin Light Chains; Renal Insufficiency, Chronic; Paraproteinemias
PubMed: 37120733
DOI: 10.1093/ndt/gfad085 -
Nephrologie & Therapeutique Aug 2021COVID-19 is a disease caused by the RNA virus SARS-CoV-2. It is characterised by an attack mainly affecting the respiratory system. There is renal involvement which is...
COVID-19 is a disease caused by the RNA virus SARS-CoV-2. It is characterised by an attack mainly affecting the respiratory system. There is renal involvement which is characterised by three main types of damage, acute tubular necrosis occurring in the most severe cases, proximal tubulopathy which is a prognostic marker of the disease and segmental and focal hyalinosis occurring in a genetically predisposed terrain. The pathophysiology of SARS-CoV-2 renal involvement is not yet defined. The direct role of the virus is debated, whereas the cytokine storm and the hypoxic and thrombotic complications seem more important. The long-term outcome of the renal damage appears to be quite good. Long-term follow-up will allow us to say whether the renal damage is part of the long COVID.
Topics: Acute Kidney Injury; Biopsy; COVID-19; COVID-19 Vaccines; Glomerulosclerosis, Focal Segmental; Humans; Kidney; Kidney Tubular Necrosis, Acute
PubMed: 34266783
DOI: 10.1016/j.nephro.2021.06.002 -
Cells Dec 2022Tubulopathy plays a central role in the pathophysiology of diabetic kidney disease (DKD). Under diabetic conditions, the kidney proximal tubule cells (KPTCs) are exposed... (Review)
Review
Tubulopathy plays a central role in the pathophysiology of diabetic kidney disease (DKD). Under diabetic conditions, the kidney proximal tubule cells (KPTCs) are exposed to an extensive amount of nutrients, most notably glucose; these nutrients deteriorate KPTCs function and promote the development and progression of DKD. Recently, the facilitative glucose transporter 2 (GLUT2) in KPTCs has emerged as a central regulator in the pathogenesis of DKD. This has been demonstrated by identifying its specific role in enhancing glucose reabsorption and glucotoxicity, and by deciphering its effect in regulating the expression of the sodium-glucose transporter 2 (SGLT2) in KPTCs. Moreover, reduction/deletion of KPTC-GLUT2 has been recently found to ameliorate DKD, raising the plausible idea of considering it as a therapeutic target against DKD. However, the underlying molecular mechanisms by which GLUT2 exerts its deleterious effects in KPTCs remain vague. Herein, we review the current findings on the proximal tubule GLUT2 biology and function under physiologic conditions, and its involvement in the pathophysiology of DKD. Furthermore, we shed new light on its cellular regulation during diabetic conditions.
Topics: Humans; Kidney; Kidney Tubules, Proximal; Glucose; Diabetic Nephropathies; Sodium-Glucose Transporter 2 Inhibitors
PubMed: 36611887
DOI: 10.3390/cells12010094 -
Clinical Kidney Journal Apr 2012Light chain proximal tubulopathy is a paraproteinemic-related kidney disease most commonly seen in patients with a plasma cell dyscrasia. The classic description is that...
Light chain proximal tubulopathy is a paraproteinemic-related kidney disease most commonly seen in patients with a plasma cell dyscrasia. The classic description is that of proximal tubules with kappa-restricted intracytoplasmic crystals in a patient with a clinical Fanconi's syndrome. Recently, other variants of light chain proximal tubulopathy have been described including those without crystal formation. We expand the morphologic spectrum in this report of a patient who presented with acute renal failure, proteinuria and hematuria. Biopsy revealed proximal tubulopathy in which the proximal tubules show intracytoplasmic amyloid formation. This is the first description, to our knowledge, of amyloid proximal tubulopathy.
PubMed: 29497513
DOI: 10.1093/ckj/sfs004 -
Pediatric Nephrology (Berlin, Germany) Oct 2017Dent disease is a rare X-linked recessive proximal tubulopathy caused by mutations in CLCN5 (Dent-1) or OCRL (Dent-2). As a rule, total protein excretion (TPE) is low in... (Review)
Review
BACKGROUND
Dent disease is a rare X-linked recessive proximal tubulopathy caused by mutations in CLCN5 (Dent-1) or OCRL (Dent-2). As a rule, total protein excretion (TPE) is low in tubular proteinuria compared with glomerular disease. Several authors have reported nephrotic-range proteinuria (NP) and glomerulosclerosis in Dent disease. Therefore, we aimed to analyze protein excretion in patients with documented CLCN5 or OCRL mutations in a systematic literature review.
DESIGN
PubMed and Embase were searched for cases with documented CLCN5 or OCRL mutations and (semi-)quantitative data on protein excretion. The most reliable data (i.e., TPE > protein-creatinine ratio > Albustix) was used for NP classification.
RESULTS
Data were available on 148 patients from 47 reports: 126 had a CLCN5 and 22 an OCRLmutation. TPE was not significantly different between both forms (p = 0.11). Fifty-five of 126 (43.7 %) Dent-1 vs 13/22 (59.1 %) Dent-2 patients met the definition of NP (p = 0.25). Serum albumin was normal in all reported cases (24/148). Glomerulosclerosis was noted in 20/32 kidney biopsies and was strongly related to tubulointerstitial fibrosis, but not to kidney function or proteinuria.
CONCLUSION
More than half of the patients with both forms of Dent disease have NP, and the presence of low molecular weight proteinuria in a patient with NP in the absence of edema and hypoalbuminemia should prompt genetic testing. Even with normal renal function, glomerulosclerosis and tubulointerstitial fibrosis are present in Dent disease. The role of proteinuria in the course of the disease needs to be examined further in longitudinal studies.
Topics: Biopsy; Chloride Channels; Dent Disease; Genetic Testing; Humans; Kidney; Mutation; Nephritis, Interstitial; Phosphoric Monoester Hydrolases; Proteinuria; Renal Elimination; Serum Albumin
PubMed: 27757584
DOI: 10.1007/s00467-016-3499-x