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1/12. Renal granulomatous sarcoidosis in childhood: a report of 11 cases and a review of the literature.

    We analysed retrospectively 11 children with renal granulomatous sarcoidosis confirmed by renal histology in order to describe the course and prognosis of the disease. Symptomatic sarcoidosis was diagnosed at a mean age of 10.1 years. Nine children had renal involvement at the time of diagnosis. In the course of the disease, nine patients developed renal failure and mild proteinuria, seven had transient sterile leukocyturia, four showed microscopic haematuria, seven had a urinary concentrating defect, and enlarged kidneys were seen in three patients. One child had hypercalcaemia and hypercalciuria, none had hypertension. light microscopy of the kidney showed interstitial infiltration by mononuclear cells in all children, interstitial fibrosis in nine patients, epithelioid granulomas in seven, tubular involvement in eight, and mild glomerular involvement in seven patients. Renal immunofluorescence was negative. Ten children received prednisone for 1-11 years. After a mean follow up of 5.5 years, three patients had entered end-stage renal failure and one had chronic insufficiency after interruption of medical supervision and prednisone therapy. CONCLUSION: Renal failure, proteinuria, leukocyturia, haematuria, and concentration defect are the prominent features of renal granulomatous sarcoidosis in children. Steroid therapy, adjusted according to disease activity, may prevent end-stage renal failure.
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keywords = hypercalciuria
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2/12. Idiopathic external root resorption associated to hypercalciuria.

    Although external root resorption (ERR) is a physiological process in deciduous dentition, it is very infrequent in permanent dentition - where the phenomenon is related to the existence of inadequate occlusal forces, periodontal pathology and microtraumatisms, etc. However, in many cases root resorption cannot be attributed to any concrete cause; such cases are defined as idiopathic external root resorption (IERR). Epidemiological studies have found that the underlying cause can only be established in 5% of all ERR. The present study describes three cases of IERR with different degrees of involvement and associated to mild calciuria and a history of nephrolithiasis. hypercalciuria with normal blood calcium levels is usually idiopathic and exhibits a familial trait, with a prevalence of 20-40 cases per 1,000 individuals in adults. A form of hypercalciuria associated to nephrolithiasis with a mutation of the CLCN5 gene has been identified, involving low molecular weight proteinuria - though this mutation has not been uniformly demonstrated in most cases of idiopathic hypercalciuria. The peculiarity of the cases described in the present study is attributable to the coexistence of IERR with normocalcemic hypercalciuria and nephrolithiasis - thus pointing to the need for in-depth evaluation of the possible association of these three clinical situations.
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ranking = 7
keywords = hypercalciuria
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3/12. Examination of megalin in renal tubular epithelium from patients with dent disease.

    dent disease is characteristic for the urinary loss of low-molecular-weight proteins and calcium, leading to renal calcification and, in some patients, chronic renal failure. This disorder is caused by loss-of-function mutations in the renal chloride channel gene, CLCN5. The animal model of this disease has demonstrated the possible role of disturbed megalin expression, which is a member of the low-density lipoprotein receptor family and is associated with renal reabsorption of a variety of proteins, in dent disease. We examined the expression of megalin in the renal tubular epithelium of two unrelated patients with dent disease. One patient, whose CLCN5 gene was completely deleted, showed significantly decreased staining of megalin compared with controls, while there was no change in another patient with partial deletion of the gene. These results demonstrated that mutation of CLCN5 in some patients with dent disease may impair the expression of megalin, resulting in abnormal calcium metabolism, manifested as hypercalciuria and nephrocalcinosis.
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keywords = hypercalciuria
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4/12. Familial hypomagnesemia with hypercalciuria and nephrocalcinosis associated with CLDN16 mutations.

    Familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC), an autosomal recessive renal tubular disorder, is characterized by the impaired tubular reabsorption of magnesium and calcium in the thick ascending limb of the loop of henle and an eventual progression to end-stage renal disease. Recent studies have reported that this disease is caused by mutations in the CLDN16 gene, which encodes the tight junction protein, paracellin-1. Paracellin-1 belongs to the claudin family and regulates the paracellular transport of magnesium and calcium. Here, we report on two Korean siblings with typical clinical features of FHHNC in association with compound heterozygous mutations, G233C and 800delG, in CLDN16. Their parents were asymptomatic heterozygous carriers of the single mutations. This is the first report of FHHNC in korea, and the mutations reported are novel.
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keywords = hypercalciuria
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5/12. Familial hypomagnesemia with hypercalciuria and nephrocalcinosis: blocking endocytosis restores surface expression of a novel Claudin-16 mutant that lacks the entire C-terminal cytosolic tail.

    Mutations in the gene for Claudin-16 (CLDN16) are linked to familial hypomagnesemia with hypercalciuria and nephrocalcinosis (FHHNC), a renal Mg2 and Ca2 wasting disorder that leads to progressive kidney failure. More than 20 mutations have been identified in CLDN16, which, with a single exception, affect one of two extracellular loops or one of four transmembrane domains of the encoded protein. Here, we describe a novel missense mutation, Cldn16 L203X, which deletes the entire C-terminal cytosolic domain of the protein. Surface expression of Cldn16 L203X is strongly reduced and the protein is instead found in the endoplasmic reticulum (ER) and lysosomes. ER-retained Cldn16 L203X is subject to proteasomal degradation. Cldn16 L203X present in lysosomes reaches this compartment following transport to the plasma membrane and endocytosis. Blocking clathrin-mediated endocytosis increases surface expression of Cldn16 L203X. Thus, endocytosis inhibitors may provide a novel therapeutic approach for FHHNC patients carrying particular Cldn16 mutations.
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ranking = 5
keywords = hypercalciuria
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6/12. Albright's osteodystrophy in a patient with renal hypercalciuria.

    We have investigated an 18-yr-old hypercalciuric female with features of both renal hypercalciuria and pseudohypoparathyroidism. She had increased circulating parathyroid hormone levels, which are common to both diseases. She also had a modest hypocalcemia and low normal basal cAMP excretion, both of which are more likely to occur in pseudohypoparathyroidism. She also had Albright's osteodystrophy, which is frequent in patients with pseudohypoparathyroidism and has never been reported in patients with renal hypercalciuria. In contrast to patients with pseudohypoparathyroidism, her serum 1,25-dihydroxycholecalciferol level was increased and her renal responses to parathyroid hormone infusion, including renal calcium reabsorption, were normal. This patient, therefore, raises the possibility that some patients with renal hyperalciuria may have a forme fruste of pseudohypoparathyroidism.
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ranking = 6
keywords = hypercalciuria
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7/12. Hypercalciuric rickets: metabolic studies and pathophysiological considerations.

    Extensive metabolic studies were performed in a 14-year-old boy suffering from the rare clinical entity known as childhood idiopathic hypercalciuria associated with dwarfism, renal tubular abnormalities and bone lesions. The salient features were: hyperphosphaturia with hypophosphatemia, hypercalciuria with normocalcemia, elevated serum 1,25-dihydroxycholecalciferol[1,25(OH)2D3] levels, marked intestinal hyperabsorption of calcium and phosphorus, with low serum parathyroid hormone (PTH) and urinary adenosine 3':5'-cyclic monophosphate (c-AMP). Bone biopsy confirmed the clinical and radiological diagnosis of rickets. It appears that the following pathophysiological sequence is operating: primary renal phosphate leak with hypophosphatemia, increased 1,25(OH)2D3 synthesis, enhanced intestinal calcium absorption which in turn inhibits release of PTH and c-AMP. hypercalciuria is seen to be secondary to both avid intestinal calcium absorption and depressed PTH activity, and rickets the result of phosphate depletion. Treatment with oral phosphorus only resulted in an acceleration of growth rate, cure of rickets, and return of urinary calcium excretion to normal values.
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ranking = 2
keywords = hypercalciuria
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8/12. Atypical idiopathic hypercalciuria in an adolescent.

    Idiopathic hypercalciuria (IH) in adults is recognized as a cause of urolithiasis. If IH is symptomatic, the symptoms are hematuria, renal colic, or obstructive uropathy with or without infection. In children, IH has been linked to the spectrum of urinary symptoms including hematuria, pyuria, dysuria, recurrent urinary infections, abdominal or suprapubic pain, proteinuria, and the frequency-urgency syndrome. hematuria may appear prior to the appearance of stones, and thiazide therapy appears to prevent stone formation by decreasing urinary calcium excretion. This report describes an older adolescent with hematuria and flank pain. His urinary chemistry values were not consistently typical of IH, but a thiazide trial with withdrawal challenge was diagnostic. His case is remarkable because, though essentially an adult, his disease was typical of prepubertal disease. Adolescents with unexplained urinary symptoms should be evaluated for IH. The urinary calcium-creatinine ratio may not be elevated, and timed urinary calcium may be equivocal. In some cases a thiazide trial may be valuable and cost effective.
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ranking = 5
keywords = hypercalciuria
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9/12. hypercalciuria in idiopathic fanconi syndrome.

    A 9 year old girl with idiopathic fanconi syndrome and hypercalciuria is described. In order to determine whether the increased calcium excretion was directly or indirectly due to the disturbed phosphate metabolism, the behavior of the calcium excretion during therapy, the serum levels of 1,25-dihydroxyvitamin D and parathyroid hormone, and the effect of parathyroid hormone on the renal tubules were investigated. Normal serum 1,25-dihydroxyvitamin D and parathyroid hormone levels, lack of a correlation between the serum phosphate concentration and the degree of hypercalciuria, as well as unsuccessful therapy of the hypercalciuria with oral phosphate indicate that the increased calcium excretion cannot be explained by impaired renal phosphate reabsorption. The hypercalciuria in the patient was therefore regarded as being due to a primary decrease of tubular calcium reabsorption.
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ranking = 4
keywords = hypercalciuria
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10/12. Idiopathic hypercalciuria with bilateral macular colobomata: a new variant of oculo-renal syndrome.

    Two siblings from a consanguineous family, suffering from nephrocalcinosis and nephrolithiasis caused by idiopathic hypercalciuria are described. The condition is associated with bilateral macular colobomata and tapeto-retinal degeneration. It is known that the latter can occur together with different nephropathies; however, until now it has never been described in combination with idiopathic hypercalciuria. blood calcium levels were found to be normal, calcium excretion rates were, with one exception, more than 6 mg/kg/24 h corrected for 100 ml GFR. Hypomagnesemia of 1.5 and 1.2 mg/dl and hyermagnesuria of 1.9 and 2.5 mg/kg/24 h corrected for 100 ml GFR were found in both patients. Tubular phosphate reabsorption reached 87% and 84% at serum parathormone levels of 0.34 microgram/l and 0.31 microgram/l in the two patients, respectively. Under calcium and magnesium loading the clearance rates of calcium and magnesium were raised whilst there was only a small insignificant increase in the blood levels of these cations. Acid-base titrations showed normal excretion rates of acid and base in one patient and a mild proximal tubular acidosis in the other. Quantitative investigation of the renal concentrating and diluting capacity established a decrease in the formation of the medullary concentrating gradient in both patients.
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ranking = 6
keywords = hypercalciuria
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