Isolated hypercalciuria with mutation in CLCN5: Relevance to idiopathic hypercalciuria

University of Rochester, Rochester, New York, United States
Kidney International (Impact Factor: 8.56). 02/2000; 57(1):232-9. DOI: 10.1046/j.1523-1755.2000.00774.x
Source: PubMed


Isolated hypercalciuria with mutation in CLCN5: Relevance to idiopathic hypercalciuria.
Idiopathic hypercalciuria (IH) is the most common risk factor for kidney stones and often has a genetic component. Dent's disease (X-linked nephrolithiasis) is associated with mutations in the CLCN5 chloride channel gene, and low molecular weight (LMW) proteinuria was universally observed in affected males. We sought to identify mutations in CLCN5 or abnormalities in LMW protein excretion in a large group of patients with IH and in a rat model of genetic hypercalciuria.
One hundred and seven patients with IH (82 adults and 25 children) and one asymptomatic hypercalciuric man with a known inactivating mutation in CLCN5 were studied. Secondary causes of hypercalciuria were excluded in all. The excretion of retinol-binding protein and beta2-microglobulin was measured by immunoassay in 101 patients with IH. Mutation analysis of the CLCN5 gene was performed in 32 patients with IH and in the genetic hypercalciuric stone-forming (GHS) rat strain.
LMW protein excretion was normal in 92 patients with IH, and only slight abnormalities were found in the other nine, none of whom had a mutation in CLCN5. One 27-year-old man who had a CLCN5 mutation was found to have isolated hypercalciuria without LMW proteinuria, renal failure, or other evidence of renal disease. Mutation analysis was normal in 32 patients with IH. The CLCN5 sequence was normal in the GHS rat.
Inactivation of CLCN5 can be found in the setting of hypercalciuria without other features of X-linked nephrolithiasis. However, mutations in CLCN5 do not represent a common cause of IH.

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Available from: Richard Hoopes, Apr 27, 2014
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    • "This patient was a 12-year-old male, belonging to the family group, who at the time of recruitment did not show any of the clinical signs considered. To our knowledge , this is the second case reported of a DD patient not presenting with LMWP (Scheinman et al. 2000 "
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    ABSTRACT: Dent disease (DD) is a rare X-linked recessive renal tubulopathy characterised by low-molecular-weight proteinuria (LMWP), hypercalciuria, nephrocalcinosis and/or nephrolithiasis. DD is caused by mutations in both the CLCN5 and OCRL genes. CLCN5 encodes the electrogenic chloride/proton exchanger ClC-5 which is involved in the tubular reabsorption of albumin and LMW proteins, OCRL encodes the inositol polyphosphate 5-phosphatase, and was initially associated with Lowe syndrome. In approximately 25 % of patients, no CLCN5 and OCRL mutations were detected. The aim of our study was to evaluate whether calcium phosphate metabolism disorders and their clinical complications are differently distributed among DD patients with and without CLCN5 mutations. Sixty-four male subjects were studied and classified into three groups: Group I (with CLCN5 mutations), Group II (without CLCN5 mutations) and Group III (family members with the same CLCN5 mutation). LMWP, hypercalciuria and phosphaturic tubulopathy and the consequent clinical complications nephrocalcinosis, nephrolithiasis, bone disorders, and chronic kidney disease (CKD) were considered present or absent in each patient. We found that the distribution of nephrolithiasis, bone disorders and CKD differs among patients with and without CLCN5 mutations. Only in patients harbouring CLCN5 mutations was age-independent nephrolithiasis associated with hypercalciuria, suggesting that nephrolithiasis is linked to altered proximal tubular function caused by a loss of ClC-5 function, in agreement with ClC-5 KO animal models. Similarly, only in patients harbouring CLCN5 mutations was age-independent kidney failure associated with nephrocalcinosis, suggesting that kidney failure is the consequence of a ClC-5 dysfunction, as in ClC-5 KO animal models. Bone disorders are a relevant feature of DD phenotype, as patients were mainly young males and this complication occurred independently of age. The triad of symptoms, LMWP, hypercalciuria, and nephrocalcinosis, was present in almost all patients with CLCN5 mutations but not in those without CLCN5 mutations. This lack of homogeneity of clinical manifestations suggests that the difference in phenotypes between the two groups might reflect different pathophysiological mechanisms, probably depending on the diverse genes involved. Overall, our results might suggest that in patients without CLCN5 mutations several genes instead of the prospected third DD underpin patients' phenotypes.
    SpringerPlus 09/2015; 4(1):492. DOI:10.1186/s40064-015-1294-y
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    • "The identification of mutation in either CLCN5 or OCRL1 confirms the diagnosis. However, some patients with CLCN5 mutations have been reported to have LMW proteinuria or hypercalciuria alone [34,44], and thus in the presence of an identified CLCN5 mutation, only one of the above clinical criteria may be sufficient to establish an affected status in an individual. It is important to note that the absence of clinical cataracts and the lack of severe intellectual deficit are key features that make a diagnosis of Dent disease 2, associated with OCRL1 mutations, more likely than a diagnosis of Lowe syndrome. "
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    ABSTRACT: Dent's disease is a renal tubular disorder characterized by manifestations of proximal tubule dysfunction, including low-molecular-weight proteinuria, hypercalciuria, nephrolithiasis, nephrocalcinosis, and progressive renal failure. These features are generally found in males only, and may be present in early childhood, whereas female carriers may show a milder phenotype. Prevalence is unknown; the disorder has been reported in around 250 families to date. Complications such as rickets or osteomalacia may occur. The disease is caused by mutations in either the CLCN5 (Dent disease 1) or OCRL1 (Dent disease 2) genes that are located on chromosome Xp11.22 and Xq25, respectively. CLCN5 encodes the electrogenic Cl⁻/H(+) exchanger ClC-5, which belongs to the CLC family of Cl⁻ channels/transporters. OCRL1 encodes a phosphatidylinositol bisphosphate (PIP₂) 5-phosphatase and mutations are also associated with Lowe Syndrome. The phenotype of Dent's disease is explained by the predominant expression of ClC-5 in the proximal tubule segments of the kidney. No genotype-phenotype correlation has been described thus far, and there is considerable intra-familial variability in disease severity. A few patients with Dent's disease do not harbour mutations in CLCN5 and OCRL1, pointing to the involvement of other genes. Diagnosis is based on the presence of all three of the following criteria: low-molecular-weight proteinuria, hypercalciuria and at least one of the following: nephrocalcinosis, kidney stones, hematuria, hypophosphatemia or renal insufficiency. Molecular genetic testing confirms the diagnosis. The differential diagnosis includes other causes of generalized dysfunction of the proximal tubules (renal Fanconi syndrome), hereditary, acquired, or caused by exogenous substances. Antenatal diagnosis and pre-implantation genetic testing is not advised. The care of patients with Dent's disease is supportive, focusing on the treatment of hypercalciuria and the prevention of nephrolithiasis. The vital prognosis is good in the majority of patients. Progression to end-stage renal failure occurs between the 3rd and 5th decades of life in 30-80% of affected males.
    Orphanet Journal of Rare Diseases 10/2010; 5(1):28. DOI:10.1186/1750-1172-5-28 · 3.36 Impact Factor
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    • "), the association between renal failure and renal stones, a possible clue for DD, may be overlooked. In our opinion, this hypothesis was made even stronger by considering that the diagnosis of DD may be difficult since, as previously observed, patients with CLCN5 mutations may have atypical presentations: just hypercalciuria without any other feature of the disease (Scheinman et al 2000), or ESRD without nephrocalcinosis (Wrong et al 1994). We found 32 male subjects with ESRD and a previous history of, or current, renal stone(s) whatever the composition or the X-ray appearance. "
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    ABSTRACT: Dent's disease (DD) involves nephrocalcinosis, urolithiasis, hypercalciuria, LMW proteinuria, and renal failure in various combinations. Males are affected. It is caused by mutations in the chloride channel CLCN5 gene. It has been suggested that DD is underdiagnosed, occurring in less overt forms, apparently without family history. A possible approach to this problem is to search for CLCN5 mutations in patients who may have a high prevalence of mutations: end-stage renal disease (ESRD) patients with previous calcium, struvite, or radio-opaque (CSR) stones. We looked for CLCN5 mutations in 25 males with ESRD-CSR stones selected from all of the patients (1,901 individuals, of which 1,179 were males) of 15 dialysis units in the Veneto region. One DD patient had a new DD mutation (1070 G > T) in exon 7. The new polymorphism IVS11-67 C > T was detected in intron 11 in one patient and one control. We also found 28 females with ESRD and stone history, and seven more males with ESRD and non-CSR stones. The prevalence of stone formers among dialysis patients in our region was 3.2%, much lower than the prevalence observed in older studies. Struvite stones continue to play a major role in causing stone-associated ESRD .
    Journal of Human Genetics 02/2006; 51(1):25-30. DOI:10.1007/s10038-005-0317-x · 2.46 Impact Factor
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